THE ANALYSIS OF UNFIRED PROPELLANT PARTICLES BY GAS CHROMATOGRAPHY...

THE ANALYSIS

OF

UNFIRED PROPELLANT PARTICLES

BY

GAS CHROMATOGRAPHY –

MASS SPECTROMETRY:

A

FORENSIC APPROACH

A thesis presented to the

Queensland University of Technology

in fulfilment of the requirements for the degree of

Masters of Applied Science (Research)

by

Shiona Croft Bachelor of Applied Science

Under the Supervision of:

Dr John Bartley

School of Physical and Chemical Sciences

Queensland University of Technology

April 2008

The Analysis of Unfired Propellant Particles by Gas Chromatography-Mass Spectrometry: A Forensic Approach Shiona Croft

ii

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In Australia, the 0.22 calibre ammunition is the most encountered ammunition type

found at a crime scene [1]. Previous analysis of gun shot residue (GSR) and unfired

propellant has involved studying the inorganic constituents by Scanning Electron

Microscopy or similar technique. However, due to the heavy metal build up that

comes with some ammunition types, manufacturing companies are now making

propellant that is safer to use. Therefore, it has become appropriate to study and

analyse unfired propellant by other means. One such technique is unfired propellant

analysis by gas chromatography – mass spectrometry (GC-MS). This technique

focuses on the organic constituent make up of the propellant paying particular

attention to diphenylamine, ethyl centralite and dibutyl phthalate. It was proposed

that different batches of ammunition could be discriminated or matched to each other

by using this technique. However, since the main constituents of unfired propellant

are highly reactive, it was not possible to accomplish batch determination of

ammunition. However, by improving extraction techniques and by removing oxygen

(a catalyst for the degradation of diphenylamine) a superior method was established

to help in the analysis of unfired propellant. Furthermore, it was shown that whilst

differentiating batches of the same ammunition was not possible, the improved

methods have helped identify different types of the same brand of ammunition. With

the aid of future studies to fully explore this avenue, the analysis of unfired

propellant could one day become an integral part of forensic science.


iii

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The work contained in this thesis has not been previously submitted to meet

requirements for an award at this or any other higher education institution. To the

best of my knowledge and belief, the thesis contains no material previously

published or written by another person except where due reference is made.

Shiona Croft Date


iv

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I wish to thank all those people who over the past years have seen me through my

best and my worst….

Firstly, to my supervisor Dr John Bartley (QUT) for your advise, patience and

support throughout my research. Your expert knowledge and direction was greatly

appreciated. In particular, your considerable experience with mass spectrometry and

research methodologies. Also, for your endless endurance, patience and guidance

with regards to the thesis write up. For all your help, I thank you.

To the Queensland Police Service (Mr Gary Asmussen and the members of the

Analytical Services Unit) for allowing me to take up this research but for also giving

me the freedom to explore this project in the direction I thought most appropriate.

Thank you.

To my colleague and friend Dr Helen Panayiotou, thank you for your words of

wisdom. Your encouragement and valuable direction when I felt lost was appreciated

greatly.

To my mum and dad who has been supportive from day one. Your support,

enthusiasm and confidence in my abilities allowed me to have courage in my work.

Thank you for never allowing me to give up – although I am too stubborn to do so!

To my dear Chris, who everyday told me how proud of me he was. Thank you for

putting up with the late nights and the stress. For your love, friendship and strength –

I honestly could not have done this without you. You mean everything to me.

To my brother Kevin, who I know is very proud of me. Thanks for your support

Kev!


v

To my Ouma and Grandad, Connie and Gerald Campbell, I wish you could be here

but you are always in my thoughts. Thank you for your support and interest in my

thesis. It means so much to me that even though you are far away your love and

encouragement is not forgotten. I miss you.

To my very much loved group of friends; Scott, Niki, Amy, Mick, Nikki and

everyone else who has been there for me. Some of you have been around for more

than a decade and your love, encouragement and support is never forgotten. You all

mean the world to me and thank you for giving me the strength to go on.

Finally, to all the post graduate students whom I may not have seen as much as I

would have liked (since being off campus) but to my friend Dr Sarah Ede in

particular, who constantly inspired me and who I always knew would do great things.

Thank you.


vi

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1.1 BACKGROUND .......................................................................................... 1

1.2 THE 0.22 CALIBRE AMMUNITION .............................................................. 1

1.2.1 The Cartridge ................................................................................... 2

1.2.2 The Projectile.................................................................................... 2

1.2.3 The Propellant .................................................................................. 3

1.2.4 The Primer........................................................................................ 3

1.3 PREVIOUS WORK RELATED TO ORGANIC GUN SHOT RESIDUE OR UNFIRED

PROPELLANT ANALYSIS........................................................................................ 4

�� (;3(5,0(17$/ ......................................................................... 18

2.1 MATERIALS ............................................................................................ 18

2.2 INSTRUMENTATION ................................................................................ 18

2.3 STANDARD PREPARATION....................................................................... 19

2.4 ETHYL ACETATE ALONE PROCEDURE..................................................... 19

2.5 ETHYL ACETATE/DICHLOROMETHANE PROCEDURE............................... 19

2.6 CONSISTENCY OF PROPELLANT COMPOSITION EXPERIMENT ................. 20

2.7 EXCLUSION OF OXYGEN EXPERIMENT .................................................... 20

2.8 TYPE DETERMINATION OF WINCHESTER AMMUNITION ......................... 20

�� 5(68/76�$1'�',6&866,21 .................................................. 22

3.1 MASS SPECTRA OF UNFIRED PROPELLANT COMPONENTS ....................... 22


vii

3.1.1 Diphenylamine (C12H11N) ............................................................... 22

3.1.2 Ethyl centralite (C17H20N2O)........................................................... 24

3.1.3 Dibutyl phthalate (C16H22O4) .......................................................... 26

3.2 CONTROLLED STANDARDS ..................................................................... 28

3.2.1 Diphenylamine, ethyl centralite and dibutyl phthalate variation...... 29

3.3 THE ANALYSIS OF PROPELLANT USING ETHYL ACETATE ALONE ........... 30

3.4 REMOVAL OF THE NITROCELLULOSE COMPONENT OF PROPELLANT USING

ETHYL ACETATE AND DICHLOROMETHANE........................................................ 44

3.5 CONSISTENCY OF PROPELLANT COMPOSITION FROM A SINGLE

BOX/BATCH OF AMMUNITION ............................................................................. 53

3.6 THE EFFECTS OF EXCLUDING OXYGEN ................................................... 58

3.7 TYPE DETERMINATION OF WINCHESTER AMMUNITION......................... 65

3.7.1 Winchester Laser LR HP 2DRM41.................................................. 65

3.7.2 Winchester Expert 23DLH02........................................................... 66

3.7.3 Winchester Winner IDKE52 ............................................................ 66

3.7.4 Winchester Subsonic LR Rim fire AED1FH31................................. 67

3.7.5 Winchester Superspeed LR HV solid SDSB51.................................. 68

3.7.6 Winchester Superspeed LR HV hollow point 2DRL62...................... 69

�� &21&/86,216�$1'�)8785(�:25. ................................. 72

4.1 CONCLUSIONS ........................................................................................ 72

4.2 FUTURE WORK....................................................................................... 73

$33(1',; ............................................................................................... 74

Ethyl Centralite standard ............................................................................... 74

Dibutyl phthalate standard ............................................................................. 75

Diphenylamine standard................................................................................. 76

Winchester Laser Long Rifle Hollow point 2DRM41 ...................................... 77

Winchester Expert 23DLH02.......................................................................... 78

Winchester Winner IDKE52 ........................................................................... 79

Winchester Subsonic Long rifle Rim fire AED1FH31...................................... 80

Winchester Superspeed Long Rifle High velocity solid 2DSB51...................... 80

Winchester Superspeed long rifle high velocity hollow point 2DRL62............. 81

5()(5(1&(6 ......................................................................................... 82


viii

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Figure 1.1: Dissected view of the case [8] ................................................................ 2

Table 1.1: Elution order for constituents using HPLC-MS[29] ................................. 6

Figure 1.2 Degradation of DPA [10,11].................................................................... 7

Table 1.2: Results from Northrop[46,47] ................................................................ 15

Table 3.1: Selected target compounds (from NIST library)..................................... 22

Figure 3.1 Mass spectrum of diphenylamine........................................................... 24

Figure 3.2 Chemical structure of diphenylamine and m/z = 77 fragment ion (C6H5)

.......................................................................................................... 24

Figure 3.3: Ethyl Centralite .................................................................................... 25

Figure 3.4: Mass spectrum of ethyl centralite ......................................................... 25

Figure 3.5: Fragmentation ions of ethyl centralite................................................... 25

Figure 3.6: Fragment A = m/z 120 and Fragment B = m/z 148 ............................... 26

Figure 3.7: General structure of phthalate esters where R, R’ = CnH2n+1; n=4-

15[50] ............................................................................................... 26

Figure 3.8: Characteristic fragmentation ions of butyl phthalate esters [51] ............ 27

Figure 3.9: Mass spectrum and chemical structure of dibutyl phthalate................... 28

Table 3.2 DPA, EC and DBPH standard variation .................................................. 29

Table 3.3 Variation in peak area of DPA between three random propellant samples

and variation observed between the three samples ............................. 31

Figure 3.10: Diphenylamine degradation over time ................................................ 31

Figure 3.11: Sample 1 - diphenylamine degradation ............................................... 32



Figure 3.14: 2-nitro-diphenylamine amounts detected (three random samples) –

Extrapolated to time zero to give appreciation of initial amounts of 2-

nitro-DPA in each sample.................................................................. 34

Figure 3.15: Mechanisms of N-Nitroso-DPA in the presence of NO2 and O2 [16] ... 36

Figure 3.16: Lussier and Gagnon [14]: Concentration of DPA and its derivatives as a

function of added nitrogen dioxide .................................................... 37


ix

Figure 3.17: Effect of storage on diphenylamine concentration (sample one and two)

.......................................................................................................... 38

Figure 3.18: Sample 1 - Effect of storage on diphenylamine (triplicate).................. 39

Figure 3.19: Sample 1 - The effect of storage on 2- nitro-diphenylamine (analysed

three times) ....................................................................................... 40

Figure 3.20: Sample one and two analysed each three times (average): comparison

between stored samples and samples left in solution for one week..... 41

Figure 3.21: The effect of leaving propellant in solution over one week (2-nitro-DPA

average – each sample analysed three times) ..................................... 42

Figure 3.22: Diphenylamine response (EtAc/Ch2Cl2 procedure) ............................. 45

Figure 3.23: Comparison between EtAc alone and EtAc/CH2Cl2 on DPA (average)

.......................................................................................................... 46

Figure 3.24: Comparison of EtAc alone and EtAc/CH2Cl2 procedures - 2-nitro-dpa

(average: each sample analysed three times)...................................... 47

Figure 3.25: 2-nitro-dpa levels - sample 1: comparison between EtAc alone and

EtAc/CH2Cl2 procedures ................................................................... 48

Figure 3.26: Comparison between EtAc alone and EtAc/CH2Cl2 procedures (ethyl

centralite average) ............................................................................. 50

Figure 3.27: Dibutyl phthalate – comparison between EtAc alone and EtAc/CH2Cl2

procedures......................................................................................... 51

Table 3.4: Relationship between sample size and population size ........................... 53

Table 3.5: Masses from ten random samples from one box of ammunition ............. 53

Figure 3.28: Levels of diphenylamine of ten (10) random samples of propellant from

the one box of ammunition ................................................................ 55

Figure 3.29: Levels of dibutyl phthalate detected of ten (10) random samples of

propellant from the one box of ammunition ....................................... 55

Table 3.6: Ratios (peak area) of main constituents from one box of ammunition .... 56

Figure 3.30 Inert gas procedure consequences on the main constituents of unfired

propellant particles ............................................................................ 58

Figure 3.31: Inert gas procedure (dibutyl phthalate)................................................ 60

Figure 3.32: The effects of leaving propellant in solution under an inert atmosphere

.......................................................................................................... 61


x

Figures 3.33: Re-analysis of samples A-D 24 hours later (individually separated for

visual clarity) .................................................................................... 63

Figure 3.34: Winchester Laser LR HP 2DRM41 .................................................... 65

Figure 3.35: Winchester Expert 23DLH02 ............................................................. 66

Figure 3.36: Winchester Winner IDKE52............................................................... 67

Figure 3.37: Winchester Subsonic LR Rim fire AED1FH31................................... 68

Figure 3.38: Winchester Superspeed LR HV solid 2DSB51 ................................... 69

Figure 3.39: Winchester Superspeed LR HV hollow point 2DRL62 ....................... 70

Table 3.7: Type determination of Winchester ammunition...................................... 71


xi

$%%5(9,$7,216�CH2Cl2: Dichloromethane

DBPH: Dibutyl phthalate

DEPH: Diethyl phthalate

DNT: 2,4-dinitrotoluene

DPA: Diphenylamine

EC: Ethyl centralite

EtAc: Ethyl Acetate

GC-MS: Gas chromatography – mass spectrometry

GSR: Gun shot residue

HP: Hollow Point

HPLC: High performance liquid chromatography

HV: High Velocity

LC: Liquid chromatography

LR: Long Rifle

MC: Methyl centralite

NC: Nitrocellulose

NG: Nitro-glycerine

N-nitroso-DPA: N-nitroso-diphenylamine

OGSR: Organic gun shot residue

SEM: Scanning electron microscopy

THC: Tetrahydrocannabinol

THC acid: Tetrahydrocannabinol acid

TLC: Thin layer chromatography

TNT: Trinitrotoluene

2-nitro-DPA: 2-nitro diphenylamine

4-nitro-DPA: 4-nitro diphenylamine


1

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Gun shot residue analysis has evolved into a significant, integral part of forensic

science today. Increased research into methodology, detection and subsequent

examination of the gunshot residue has allowed this type of evidence to be used more

effectively by analysts for the purpose of solving crime.

One area of research that has been explored is investigating the organic constituents

of unfired propellant to identify their key role in ammunition make up and functions.

It is widely known that the inorganic components of gunshot residue are readily

analysed by the scanning electron microscope to identify lead, barium and antimony

and other key ingredients[2-5]. However, the potential health risks associated with

heavy metal build up, have led to heavy metal free ammunition being introduced [6].

In this situation, organic analysis of the residue or propellant is required and

subsequently, analysts have demonstrated that this is possible. There are some

discrepancies though with which constituents are unique to smokeless powders,

which will aid in the identification of the ammunition.

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In Australia, the use of 0.22 calibre ammunition is wide spread[1] and so,

investigative forces are mostly concerned with this type of ammunition. To fully

appreciate the diversity of the 0.22 calibre projectile some background information

will be given about the physical make up of ammunition itself, including: the

cartridge and cartridge case, projectile, propellant; and primer and their roles in the

organic make-up of the ammunition[1,7].


2

1.2.1 The Cartridge

The calibre of the ammunition refers to the diameter of the bore inside the firearm. A

typical cartridge will contain the case, primer, propellant and projectile. The

ammunition can either be rim fire or centre fire. In rim fire ammunition, the priming

materials are concentrated around the outer edge of the base of the cartridge making

the rim the most susceptible to detonation. Conversely, centre fire concentrates the

priming material into the centre of the base of the cartridge leading to this centre

being the most susceptible to ignition.

Figure 1.1: Dissected view of the case [8]

1.2.2 The Projectile

Lands and grooves are often marked onto fired projectiles as they spiral out of the

muzzle of the firearm. These physical striations can help in the physical

characterisation of the projectile through the use of a comparison microscope. The

shape, cannelures, dimensions of the hollow point and coating can all be

discriminating identifiers of the projectile origin. It is known that the inorganic

composition of the projectile is usually lead, or lead with antimony added as a

hardener[2,4,5,9].

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This figure is not available online. Please consult the hardcopy thesis available from the QUT Library


3

1.2.3 The Propellant

The most important part of the ammunition in relation to analysis is the propellant.

The propellant occupies considerable space inside the cartridge case and contains

various compounds. For 0.22 calibre ammunitions, smokeless powders are the

propellant of choice[1]. These powders come in two varieties, single and double

based. Single based powders are those that contain nitrocellulose (NC) as the main

explosive material whereas double based powders contain both NC and nitro-

glycerine (NG). The addition of NG increases the hydrophobic tendencies of the

powder, raises the energy content and softens the powder. The stabilizers ethyl and

methyl centralite behave in a chemically similar way however, only one compound is

used in the ammunition make up, never both. The role of these compounds is to

remove oxides formed by the decomposition of NG and NC. If these oxides are not

removed, they behave as catalysts and are involved in further decomposition, which

will shorten the shelf life of the ammunition. It has also been stated that self-ignition

may occur from the increased degradation due to the auto-catalysis[10-17] of the

ammunition. Ethyl centralite (EC) removes oxides by acting as a weak base and

reacts with the decomposition products to form nitro and nitroso derivates.

Diphenylamine (DPA) is another stabilizer commonly seen in single based powders.

Its usual concentration is only 1% and it is common to see both EC and DPA in

ammunition types. Its function is similar to that of EC, as its main function is to

absorb the free nitrates that have derived from the nitrocellulose. Its degradation and

the subsequent derivatives that are formed will be discussed later in the chapter.

Plasticizers are also found in propellants and work to convert NC from its natural

fibrous state into a gel state. Dibutyl phthalate, diethyl phthalate, dioctyl phthalate,

and glycerol triacetate are common plasticizers found in ammunition today[9,18].

These compounds can also function as burning modifiers which reduce the initial

burning rate of the propellant grains and increase pressure and efficiency[19].

1.2.4 The Primer


4

Most primers have explosive and oxidizing properties. Many of the compounds

found in primers can be multi or mono functional. Organic compounds with nitro

functional groups are often used as primers. Such compounds include Trinitrotoluene

(TNT) or derivatives thereof. In addition to these organic compounds mentioned,

primers are also comprised of inorganic elements such as barium, lead and antimony.

These elements play key roles; for instance, an initiator (lead styphnate), an oxidiser

(barium nitrate) and a fuel source (antimony sulphide)[2,5,9,18,20].

The primer is ignited when hit by the firing pin of the weapon which results in hot

gases and temperatures being created. The ignited primer now decomposes and the

enormous pressure and energy build up consequently causes the projectile to be

expelled from the chamber of the firearm. Lead, Antimony and barium are converted

into a gas during this process which in turn condenses into tiny spheres or droplets of

residue. These spheres can range in size from 0.5 to 10 microns, making them a

valuable tool in forensic science.

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The use of Gas Chromatography-Mass Spectrometry (GC-MS) as a method for

analysing organic compounds in the forensic field is well established in areas such as

drug analysis, which suggests it could be extended to GSR research. Aebi et al[21]

has stated that GC coupled with dual MS and a Nitrogen-Phosphorous Detector

(NPD) is a powerful tool for forensic analysis. Their study concentrated on

identifying masked pharmacologically active compounds via this method and noting

its advantages over other detection systems. However, they observed that not all

pharmacologically active compounds contain nitrogen and phosphorous. Their

LQYHVWLJDWLRQ�RI� ��– tetrahydrocannabinol and its metabolites (THC acid) show this.

This compound is the active component in marijuana or cannabis, is non volatile and

therefore Liquid Chromatography (LC) is often used to establish the concentration of

THC in a particular sample. The reason for this is because with higher temperatures

often used within a GC system, THC acid is decarboxylated to THC. This

subsequently results in an inaccurate estimation of the total concentration of THC in


5

the sample. This is of significance as a small amount of THC acid decarboxylating to

THC in this process has a dramatic effect on the amount of THC detected. In their

study, while not covering a large number of compounds, did show the possible

advantages of using GC-MS in organic studies of this nature. GC allows for rapid

and sensitive separation of compounds while MS provides identification of the

resulting peaks from the chromatogram. By using mass spectral libraries, unknown

substances can usually be identified. This in turn has allowed GC-MS to be a

valuable tool in forensic analysis and will continue to do so in the future, with many

studies utilising this analytical technique[22-25].

Within the field of unfired propellant analysis, the organic compounds used for

identification have not changed significantly over the years, however, major

discrepancies exist over which of these organic compounds are totally ‘unique’ to

smokeless powders.

Mach undertook two studies in 1977[26] and 1978[27] of 33 different kinds of

ammunition to determine the feasibility of identifying gunshot residue via its organic

constituents using GC-MS. From their earlier study[26] they were not able to predict

the composition of the powder just by its brand and type. Their later study[27] agreed

with Wu et al[28,29] that the main characteristic compound is ethyl centralite but it

is present in comparatively small amounts. Mach’s work did not extend to

discriminating different batches of ammunition. Their main focus was on comparing

the unburnt particles to burnt ones. The results indicated the components detected

were of varying concentrations. It could have been useful, therefore, to establish a

database of the concentrations of the various components detected. Unknown

samples could have been compared to this database to establish whether it had

similar properties to the samples of known origin in the database (i.e. a profiling

method). Interestingly, their results showed that diphenylamine was the most

common additive, and while this is not a new discovery, the lack of investigation into

other organic compounds in the samples would indicate their method is in need of

further exploration. Dibutyl phthalate was seen in about half of their samples but

nitro-glycerine was seen in a substantial number of samples, which suggests that

their work was paving the way for further investigations into this area.


6

Wu et al[29] used a tandem mass spectrometry system (MS-MS) to show that the

organic components of GSR are more characteristic than their inorganic counterparts.

MS-MS has the added advantage of being more selective in that molecular ions are

separated by the first mass spectrometer, and these subsequent selected ions are

reanalysed by a second mass spectrometer to give a more specific pattern. It was

stated that the main components of the gunshot residue are NG, trinitrotoluene

(TNT), 2, 4-dinitrotoluene (DNT), DPA and methyl centralite (MC). In their research

they were able to separate the main components of the gunshot residue by High

Performance Liquid Chromatography (HPLC) and observe the molecular ions of the

main stabilizer methyl centralite, which are said to be the most characteristic

compounds of gunshot residue[28]. The components were analysed by HPLC-MS

and the compounds eluted in the following order (table 1.1):

Table 1.1: Elution order for constituents using HPLC-MS[29]

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When the compounds were then subjected to MS, characteristic ions were seen. This

however, was done using negative ion mass spectrometry which is not the usual

methodology. The Molecular ion (M-H)- at m/z 226 was seen with fragmentation

ions: (M-HNO3)- at m/z 163 and (NO3)

- at m/z 62. These ions are said to be

characteristic of NG[29]. The characteristic molecular ion of MC was seen at m/z

241 and the fragmentation ions at m/z 134, 106, 77, 51. While it has been suggested

that the various components of the smokeless powder do have other origins, MC and

EC are thought to be characteristic of smokeless powders especially when seen with

NG[28]. These two compounds are uncommon in other industries. NC, on the other

hand, is used in lacquers, varnishes, printing and in the pharmaceutical industries

while DPA is used in rubber preparations and in the food industry. NG has uses in

the explosive and pharmaceutical industries[28].

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This table is not available online. Please consult the hardcopy thesis available from the QUT Library


7

Wu et al [29] did however suggest that by focusing their studies on methyl centralite

and using concentrated sample volumes, the level of contamination of the injector

contributed to lower than expected detection levels. Several cleaning methods did not

help the situation and so, they adopted a 100 fold dilution of the samples with

methanol to avoid further contamination. Once this method was adopted, they were

able to successfully discriminate 10 persons who had recently fired a revolver, from

10 persons who had not fired a gun. Further experiments could adequately identify

MC on a person who had fired a pistol eight hours earlier and on the hand of an

individual who had washed their hands after firing a pistol. Both tests showed a

positive correlation and they argued that their work could be used in criminal

investigations when an offender managed to escape after firing a firearm, but was

caught several hours later. They proposed that even if the offender washed their

hands with water, detectable amounts of MC could be identified using this method.

This method was found to be sensitive and selective when using Multiple Reaction

Monitoring (MRM) mode, which used ions of m/z 241 as precursor ions and ions of

m/z 134 as product ions, and while their method mainly focused on methyl centralite,

it could be adapted to identify other components, and therefore is a promising

technique.

While Wu et al [29] concentrated on MC as the most characteristic compound for the

identification of smokeless powders; DPA and its derivates have received wide

attention. It is known to decompose substantially[10-17,30-35] and Tong et al[17]

suggested that the ‘detection of DPA may be taken as evidence’ as many gun

powders do not contain the stabilizers methyl or ethyl centralite. However, it should

be noted that DPA is also found in the rubber and food industry.

[2-nitro-DPA]

[DPA] [N-nitroso-DPA]

[4-nitro-DPA]

Figure 1.2 Degradation of DPA [10,11]


8

Bergens and Danielsson[10,11] investigated the degradation mechanism of DPA and

their results are shown above in figure 1.2, however, this is in contradiction to the

report of Lussier[14] who suggested other reaction mechanisms. Bergens and

Danielsson concentrated on monitoring the DPA at a temperature of 85ÛC to note the

breakdown products achieved. The conclusion was after analysis by LC, only a small

percentage of the DPA is converted to 2-nitro-DPA and 4-nitro-DPA. Conversely, N-

nitroso DPA corresponds to the largest breakdown product produced, which in turn is

responsible for further interaction with the NC degradation products. After 15 days

of storage at this temperature, the concentration of the 4-nitro-DPA is about twice as

much as 2-nitro-DPA which is supported by the work by Lussier and Gagnon[14].

The concentration-time curves further support the idea that the DPA is rapidly

degraded into these products when introduced to a NC matrix.

Concentration anomalies of DPA were observed in another study[14] which

encountered difficulties during extraction stages; however in the study, critical

evaluation of their extraction and solvent techniques have rendered the paper quite

useful. The cause of the significant DPA loss was not fully explained, and while it is

of extreme importance to understand the chemistry of the reactions, the authors have

suggested that the interaction between the NC matrix and DPA has produced a

compound not amenable to extraction techniques. Methylene chloride was used

suggesting that most of the NC matrix should have been removed during the

extraction stage. It does then beg the question of what DPA is reacting with to create

degradation products. The authors gave many possible explanations including the

interaction with nitrate esters, causing cleavage to leave alkoxy radicals, which are

said to be responsible for rupture of the cellulose chain. Furthermore, the NC-DPA

structure that is then formed could react with nitrous oxides and N-nitroso-DPA, with

2 and 4-nitro-DPA possibly being by-products of this interaction. In part 2 of the

study[10] it was suggested that spectroscopic techniques be employed to determine

whether or not the DPA has been incorporated into the NC matrix. While more

complex reasons were suggested for the DPA degradation, it is important to note the

possible interaction with oxygen as a degradation source[11]. The authors did not

give reasons behind the reaction between DPA and oxygen nor its interaction with


9

light. It may be worth investigating these two physical properties on the

decomposition of DPA.

Mathis et al [36] further highlighted the importance of developing an analytical tool

for the characterisation of GSR. Their study involved seven compounds; DPA, N-

nitroso-DPA, MC, EC, dimethylphalate, diethylphthalate and dibutylphthalate

(DBPH). Mathis et al understood the necessity of producing a chemical profile that

allows for determination of distinguishable characteristics. While they acknowledged

the use of GC as a tool for the analysis of GSR, the study involved the use of

gradient reversed phase liquid chromatography as it was felt that the nitro

compounds were susceptible to thermal degradation by GC-MS. This contrasts with

the work of Burns et al[22] who used GC-MS to analyse and characterise NG based

explosives. Burns et al successfully identified nitro esters and nitro aromatic

compounds from the samples and undertook the important task of examining any

batch-to-batch differences between commercial explosives. Determination of the

sample’s total DNT content allowed for further discrimination of the ammunition

type. This information was compared to the manufacturer’s specifications, which

enabled the explosive batch number to be established.

Despite the contradiction, Mathis et al were able to quantify several organic

constituents such as centralites, phthalates and diphenylamine by gradient reversed

phase LC. This phase was chosen due to the spread in polarities of the main

constituents. Coupled with MS, this technique is very powerful in both separating

and identifying capabilities. The separation method was further developed by

Wissinger et al in 2002[37] however slight changes were made to accommodate

Mathis’ study. Ammonium acetate (CH3COONH4) was used to assist the ionisation

process. Methylene chloride as a an extraction solvent was also used as its

application is well documented in OGSR[10,11,25,37]. Its role is to keep the NG

insoluble, which enables ease of removal upon reconstitution. The LC conditions

were modified compared to those used by Wissinger by using a lower flow rate,

smaller column and by adding ammonium acetate to the mobile phase to help in the

ionization stage. The study was significant to GSR analysis as it successfully

discriminated characteristic organic compounds; however, the ambiguity of the


10

conclusions reduces the overall value of the work. Wissinger did comment on the

power of GC-MS, particularly with respect to the analysis of phthalates which may

have been missed by LC-MS.

In 1989, Keto et al[18] compared smokeless powders using Pyrolysis Capillary Gas

Chromatography. This method was chosen since there is no sample preparation

involved and consequently any error associated is eliminated. The authors also

argued that by using the capillary column, the better separation would increase the

analytical benefit. Meng et al [20]agreed with this statement by saying that the

‘separating power of the capillary column in the GC is unparalleled’. However, by

using statistical measurements, the amount of detectable difference between

manufacturers was shown to be very small, rendering this method limited in source

identification. This is a situation where the use of MS could be of significance to

properly identify the peaks in the chromatogram. While no real differences seen

between different manufacturers, close examination of the results showed different

levels of peak intensity, which was not appropriately recognised in the paper. The

size of the study was limited to only three samples: Hercules Red Dot; Winchester-

Western 540; and Dupont Hi-Skor 700x brands. This factor could be the reason for

their poor results. Many brands and types of ammunition should have been included,

especially when their statistical method of validation is a chemometric method,

which requires a large sample population.

In a survey of GSR analysis by Meng et al[9], efforts were made to compare the

various techniques available for the study of GSR. They incorporated both inorganic

and organic analysis. From this report, it is clear that there is a variety of techniques

available for analysis of the organic components, whereas in inorganic analysis there

are only four main instruments of choice: Atomic Absorption Spectrometry (AAS);

Anodic Stripping Voltammetry (ASV); Neutron Activation analysis (NAA); and

Scanning Electron Microscopy coupled with the Energy Dispersive X-Ray detector

(SEM/EDX). When analysing the organic components, there is a greater variety of

methods to choose from. Such techniques include Thin Layer Chromatography

(TLC); Gas Chromatography (GC); Infrared Spectroscopy (IR); High Performance

Liquid Chromatography (HPLC); Mass Spectrometry (MS); Fluorometric detection;


11

Supercritical Fluid Chromatography (SFC) and Capillary Electrophoresis (CE). The

use of Raman Microscopy has also been noted in Organic GSR analysis[38]. More

recently, the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) has

been noted in the study and characterisation of propellant samples[39,40]. This

analytical technique has the advantage of obtaining elemental and molecular

information from surface samples with a particularly low level of detection. It can

also capture molecular images which may be useful for investigating distribution of

additives and explosives constituents of the powder.

TLC has the advantage of being simple, rapid, moderately sensitive and relatively

cheap. However, it has poor quantification capabilities and requires a large amount

of sample. Infrared Spectroscopy (IR) has been successfully used to determine the

presence of nitrocellulose in samples[41]. However, it was not as successful in

determining the other minor components present at low concentration, but which are

equally important in function. Such components include the stabilizers in the

propellant grains, which may be used as characteristic compounds of GSR.

Furthermore, the fact that only NC (not being totally unique to GSR) was accurately

detected in this study may render this technique unsuitable for the analysis of GSR,

as there are many other vital components, which have been overlooked. It may be

useful for the confirmation of substances when a positive result using another

method such as HPLC, has been obtained.

HPLC can be used for the analysis of organic compounds and has the added

advantage of being able to separate ionic compounds, polymeric materials and poly-

functional compounds of high molecular weight. Also, HPLC is not limited by

thermal stability of the compounds. Due to the higher temperatures in the GC

instrument, some compounds cannot be adequately analysed as they may undergo

decomposition during injection.

The MS system is a highly specific and sensitive method and has previously been

shown to be a powerful tool in analysing explosive compound[28,29]. Mass

Spectrometry is an excellent analytical system which is best coupled with the GC or

HPLC systems to give both separation and identification of the compounds in a


12

mixture. It has been proposed that the coupling of MS with GC will render the best

results since both operate in the gaseous phase and the separated components can

sequentially flow to the MS detector where the individual mass spectra can be

obtained[21]. Most investigations into the organic compounds of GSR have coupled

the MS with HPLC but the use of GC is equally as valid.

Fluorometric detection has been noted as a sensitive and selective mode of detecting

organic components when using HPLC. Meng et al[20] in 1996 investigated the

detection of ethyl centralite and 2-4 DNT in GSR after derivatisation with 9-

fluorenylmethylchlorformate. Their method used a fluorometric detection which they

claimed to be a more sensitive and selective method for the detection of organic

GSR. EC was first hydrolysed to N-ethylaniline (NEA), which was further

derivatised with dansyl chloride (DNS-Cl). The end product was a fluorescent

compound that could be separated using TLC or reversed phase HPLC. While the

authors claim that fluorometric detection is sensitive and selective, their analysis

revealed that only three out of eleven kinds of ammunition contained EC. They

analysed three other compounds recommended as characteristic compounds[35].

These were 2,4 DNT, 2–nitro diphenylamine, and 4–nitro diphenylamine. It is

suggested that they can be reduced to their aromatic amines which then allows for

derivatisation using the labelling agents such as 9-fluorenylmethylchloroformate

(FMOC). Interestingly, the use of diphenylamine derivatives is in complete

contradiction to their previous statement in 1994[42] where they stated that, ‘DPA

has been regarded as an evidentially irrelevant compound’. The authors were able to

achieve good detection levels (1 pg levels) which is lower than their previous

detection limits of 60pg using DNS-Cl[42]. However, only six out of eleven samples

were shown to contain EC or 2, 4-DNT or a combination thereof. Their method

failed to detect the other two compounds previously mentioned to be more

characteristic than EC and DNT. The authors suggested that while the method may

be sensitive, further analysis of the reduction, hydrolysis, derivatisation and

fluorescent steps could ultimately improve the technique.

The use of Supercritical Fluid Chromatography (SFC) has not been extensive in the

area of organic gunshot residue analysis; however it has been reported that its


13

application is suitable for thermally labile or non-volatile substances. An advantage

of SFC is that it is compatible with virtually all detectors used in established

chromatographic techniques such as GC and HPLC. In a study by Munder et al,

smokeless powders were analysed using this technique and while they were able to

detect several minor constituents such as ethyl centralite, diphenylamine,

dinitrotoluenes and dibutyl phthalate, they were not able to distinguish between

different brands. The possibility then of classifying smokeless powders by

manufacturer using this technique is low.

An interesting example of characterising black powders is the study by MacCrehan

et al in 2002[43] who looked at associating gun powders and residues by

compositional analysis. They identified the main constituents of the powder to be

nitrocellulose, nitro-glycerine, diphenylamine and ethyl centralite. Characterisation

of the ammunition type was achieved by calculating a propellant to stabiliser ratio

(P/S ratio) developed by Reardon et al which is a simple method to use and interpret.

The study collected 7 brands with only 50 rounds in each. Each of the cartridges

were assigned numbers from 1 – 50 and the, numbers 1, 10, 20, 30, 40, 50 were

assigned codes. The powder was removed from the cartridge and placed in a vial

which could only be traced back to this code. This method then allowed for a random

choice for the order of analysis. Ultrasonic Solvent Extraction/Capillary

Electrophoresis was their method of choice and while it was adequate for detection

of certain compounds, some brands were shown to contain diphenylamine only. This

observation is unusual as powders are comprised of various substances such as

propellants, hardeners, stabilisers and so on and therefore detection of these would be

expected. To fully appreciate the characteristic associations, a more sensitive and

selective analytical procedure should be adopted so that a characteristic profile for

each cartridge could have been developed. Furthermore, as suggested by Smith et

al[44], electrophoresis should only be a complementary tool as results can vary

according to different parameters. The study however shows promise in selectivity

and sensitivity but compared to other analytical techniques, it appears that this

method is somewhat lacking. MacCrehan’s study is an example however, of how

important it is to characterise and discriminate powders from each other. This can


14

only be of benefit for investigating authorities who rely on validated databases with

which to compare their unknown samples.

Furthermore, in an important recent study by MacCrehan[45] an attempt was made to

create a smokeless powder reference material for laboratories undertaking explosive

and propellant analysis. The aim was to characterise the organic additives commonly

found in smokeless powders such as nitroglycerin, ethyl centralite, diphenylamine

and the nitration product N-nitrosodiphenylamine. This would be achieved using the

analytical techniques Micellar capillary electrophoresis (CE) and Liquid

Chromatography (LC). Three candidate smokeless powders were studied. Powder 1

was Hi Skor 700X (an NG containing powder stabilized with EC). Powder 2 was

Winchester 231 (an NG powder stabilized with DPA) and handgun reloading

smokeless powders purchased from a local gun shop. Powders 1 and 2 became the

inter laboratory comparisons of smokeless powders analysis and measurement and

interestingly, MacCrehan noted a number of inconsistencies from the 20 participants.

Many laboratories reported surprising results with some identifying EC in powder 2

which was stabilized by DPA. They report that manufacturers often use recycled

surplus of materials and this material may have different compositions than intended.

These trace compounds and inhomogeneity of the propellant lead to uncertainty of

the true make up and chemical composition of the smokeless powder. For this

reason, the commercial powders were deemed unsuitable for reference materials.

However, the use of Powder 3 (the handgun reloading smokeless powder) was

explored and through a series of experiments and involving thermal stability and

homogeneity, it was deemed that Powder 3 was suitable for reference materials with

the use of LC. The testing revealed that storage at room temperature or below was

acceptable and sampling sizes should be 20 mg or greater. These conclusions were

supported by the fact that relative uncertainties for the additives were much smaller

with room temperature stored samples and of sizes 20mg or greater. The study was

able to provide a reference material from Powder 3 with a level of uncertainty <5%.

As this is a relatively new study, further follow up inter laboratory analysis and

testing should be carried out to support the long term use of such reference material.


15

Electrophoresis also has been applied to organic gunshot residue analysis [44-47].

Northrop completed a two part study[46,47] which concentrated on 13 compounds

including derivatives of the main organic constituents. This work was an extension of

previous work undertaken in 1992[48] which examined sampling protocol for

Micellar Electrokinetic Capillary Electrophoresis (MECE). Results are shown in

Table 1.2.

Table 1.2: Results from Northrop[46,47]

Compound Detection Levels (pg)

2,4 DNT 1.1

2,6-DNT 1.2

3,4-DNT 1

2,3-DNT 1.3

Diphenylamine 0.9

2-Nitrodiphenylamine 1.9

4-Nitrodiphenylamine 2.1

N-nitroso-diphenylamine 1

Dibutyl Phthalate 2.6

Diethyl Phthalate 2.2

Ethyl centralite 1.8

Methyl centralite 1.1

Nitro-glycerine 3.8

Zeichner et al[25] argued that MECE with diode array UV detector is not sensitive

enough for crime scene comparison however Northrop used this tool to develop a

method for separating organic constituents of gunpowder. Northrop argued that the

phthalate esters commonly seen in OGSR analysis are not unique to gunpowder and

have not been included in his study. While this may be the case, the detection of

phthalate esters is a confirmatory tool in the identification of smokeless powders and

their inclusion is both important and significant to the ammunition makeup. Part two

of the study[46] concentrated more on the direct examination and characterisation of

the main organic compounds of GSR. 16 out of 26 samples taken from the back of

the right hand after firing under controlled conditions, showed no detectable GSR.

The other samples were found to contain mostly nitro-glycerine, diphenylamine, and

N-nitroso diphenylamine. Two samples were shown to contain ethyl centralite and

only one sample was shown to contain all components (nitro-glycerine,

diphenylamine, N-nitroso diphenylamine, 2-nitrodiphenylamine, 4-

nitrodiphenylamine and ethyl centralite). When a 0.22 calibre weapon was used, no


16

detectable OGSR was found. It was suggested that re-testing of other 0.22 weapons

would be of use to determine whether the lack of OGSR is due to the size of the

weapon or ammunition, or because of the configuration of the weapon. This

assumption is flawed as no attempt was made to discover if the analytical techniques

and recovery procedures played a significant role here. Furthermore, it was suggested

that it may be possible for OGSR not to be deposited on skin surfaces, or that the

weapon characteristics prevent detectable OGSR from being deposited after each

firing. Further investigations into more reliable techniques could dramatically

improve the research. However, this study has demonstrated its limited use in

forensic casework which relies on validated analytical procedures for reliable

conclusions.

The important paper by Wrobel et al[1] emphasizes the necessity for a method that

combines all information pertaining to the organic make up of smokeless powders.

Their work indicated that 0.22 calibre ammunition is the most commonly

encountered projectile in Australia and it appears that this trend has not altered. The

identification of the ammunition was carried out using both physical and chemical

characteristics, which generally were from an inorganic source. A database was

created that consisted mainly of SEM/EDX spectra, which can be compared directly

from materials gathered from a crime scene. The database was useful in identifying

the cartridges from crime scenes, since physical characteristics were being included

into the database. However, the conclusions were limited due to the project

consisting mainly of inorganic substituents which unfortunately do not vary

substantially between types.

A database consisting of organic substituents could in fact be beneficial to

investigating personnel. By combining the powerful separating and identification

qualities that GC-MS possess, a database of considerable importance could be

created which ultimately should be able to differentiate the type of ammunition by

the type and quantity of organic matter present. It is vital that even though a database

could be implemented, it must be constantly reviewed with the changing times and

possible new ingredients. This idea is supported in the study by Collins et al[49]

where recent research has shown that glass containing particles in gunshot residue


17

can be analysed and characterised. Even though their study concentrated on the

inorganic components of GSR, it does raise the important point that new discoveries

are constant and analysts need to be aware of this.

Organic constituents can be more characteristic and by using GC-MS, reproducible

and repeatable results can be obtained. Due to the lack of validated GC-MS

methodology, this work will focus on establishing a tool for the forensic

investigation of gunshot residue. Previous studies have shown that GC will not be the

ideal instrumentation to analyse non-volatile substances. However, this can be

overcome by ignoring the major nitrocellulose matrix and maintaining lower port

temperatures. By doing this, it can determine the presence of the major organic

compounds by a sensitive and selective analytical tool. An instrument such as GC-

MS readily fits this description. It is important to distinguish which compounds are

unique to smokeless powders and by intercalating the literature assessed in this

survey, decisions about these compounds can be made.

As previously mentioned, the 0.22 calibre ammunition is the most commonly

encountered ammunition type recovered at a crime scene. This study will therefore

focus on using this type of ammunition. Furthermore, investigations into proper

solvent choice, developing an extraction technique to remove the nitrocellulose

matrix, will be established. To fully appreciate the possibility of matching or

discriminating propellant to a box or batch of ammunition, it is imperative that the

propellant is examined for homogeneity. Also, as previous papers have indicated,

oxygen plays a significant role in the degradation of diphenylamine, it may therefore

be important to investigate the effects of removing oxygen from the experiments.

The ultimate aim will be to determine whether it is possible to match a propellant

sample back to its batch of manufacture.


18

�� ([SHULPHQWDO��

�� 0DWHULDOV� The standard compounds DPA (99% purity), EC (98% purity) and DBPH (99%

purity) were obtained from Sigma-Aldrich (USA). HPLC-grade ethyl acetate and

dichloromethane (DCM) were obtained from Selby (Brisbane, Australia). The

propellant samples were obtained from the Ballistics section of the Queensland

Police Service (Brisbane, Australia). The GC vials and 300µL glass inserts were

obtained from Biolab (Brisbane, Australia).

�� ,QVWUXPHQWDWLRQ�

The GC-MS consisted of a Hewlett Packard HP6890 Series GC system and 5973

Series Mass Selective Detector (Agilent Technologies) equipped with an auto

sampler and injector. Chromatography was achieved using a DB-1 capillary column

(0.25mm x 30m x 0.25µm) using a pulsed splitless injection technique at one ml/min.

The oven initial temperature was set at 50 degrees for one minute with an

equilibration time of 0.2 minutes. A rate of six degrees per minute was selected to

reach a maximum of 270 degrees. The front inlet had a temperature of 250 degrees

with a pulse pressure of 40 psi. The MSD transfer line heater was set at 280 degrees.

1µL of sample was injected into the GC with a total run time for each sample being

45.7 minutes. EI was used over a mass range of 29-300 amu and an operating voltage

of 70eV. MS Chemstation software (Hewlett Packard) was used for automation and

data analysis. Each sample was analysed under these conditions and was used for the

detection of all compounds except nitro-glycerine. Unless stated otherwise, NIST

library was used for compound identification.

To analyse nitro-glycerine, another pulsed split-less technique was used. The same

operating parameters as previously described were used; however, the initial front

inlet temperature was set at 150 degrees and a sampling volume of 2µL was used. As


19

all samples analysed in this study were double based in nature (i.e. it contained both

NG and NC), it was decided that analysis of NG would not be efficient.

�� 6WDQGDUG�SUHSDUDWLRQ�

To gain an understanding of the instrumental variation, standard solutions for DPA,

EC and DBPH were made. This was done by dissolving in volumetric flasks 5mg in

50 ml ethyl acetate (0.01% w/v) for DPA and 100mg in 100ml ethyl acetate (0.1%

w/v) for EC and DBPH. Three stock solutions containing DPA was made and ten

stock solutions for EC and DBPH were made. An aliquot from each stock solution

was taken and analysed. Due to limited availability of DPA, three stock solutions

could only be made.

�� (WK\O�DFHWDWH�DORQH�SURFHGXUH�

Three random rounds of ammunition were obtained from Winchester 0.22 Expediter

with batch number ADD1BGH2. 50mg of the propellant from each projectile was

accurately weighed and dissolved into three separate volumetric flasks with 5ml of

ethyl acetate in each. An aliquot from each volumetric flask was taken and placed in

a 2ml GC vial labelled sample 1, 2 and 3. Each of the vials was analysed three times

to gain an understanding of the variation caused by this dissolution method.

�� (WK\O�DFHWDWH�GLFKORURPHWKDQH�SURFHGXUH��

One random projectile was obtained from the same batch of ammunition as

previously stated. 50mg of the propellant was accurately weighed and dissolved into

a 5 ml volumetric flask with 5ml of ethyl acetate. Three separate aliquots of 0.3ml

were taken and placed into three separate GC vials labelled 1, 2 and 3. Each vial was

evaporated to dryness with an inert gas (nitrogen) and then reconstituted in 0.3ml of

dichloromethane. The reconstituted samples were then placed in a new GC vials with

a 300µL glass inserts. Each of the vials were analysed three times to gain an

understanding of the variation caused by the extraction technique.


20

�� &RQVLVWHQF\�RI�SURSHOODQW�FRPSRVLWLRQ�H[SHULPHQW�

Ten random projectiles were obtained from Winchester Superspeed 0.22 with batch

number 2DSM92. 50mg of the propellant was accurately weighed and dissolved into

a volumetric flask with 5ml of ethyl acetate. An aliquot of 0.3ml was taken and

placed into a separate GC vial. The vial was brought to dryness with an inert gas

(nitrogen) and then reconstituted in 0.3ml of dichloromethane. The reconstituted

sample was then placed in a new GC vials with a 300µL glass inserts. Each of the ten

samples were made and analysed one at a time to reduce any effect caused by oxygen

and light on the degradation of the propellant.

�� ([FOXVLRQ�RI�R[\JHQ�H[SHULPHQW�

Five random projectiles were again obtained from the same batch of ammunition as

previously stated. 50mg of the propellant was accurately weighed and dissolved into

a volumetric flask with 5ml of ethyl acetate. Each of the five samples were made and

analysed one at a time. All manipulations were carried out in a nitrogen filled glove

box which had been allowed to flush to remove oxygen for 24 hours. During the

experiment, the N2 flow was maintained at 2ml/min.

�� 7\SH�GHWHUPLQDWLRQ�RI�:LQFKHVWHU�DPPXQLWLRQ�

Six different types of Winchester brand 0.22 ammunition were selected; (1)

Winchester laser Long Rifle High Performance with batch number 2DRM41, (2)

Winchester Expert with batch number 23DLH02, (3) Winchester winner with batch

number IDKE52, (4) Winchester subsonic long rifle rim fire with batch number

AED1FH31, (5) Winchester super speed long rifle high velocity solid with batch

number 2DSB51 and (6) Winchester super speed long rifle high velocity high

performance with batch number 2DLRL62. From each type of ammunition listed two

projectiles were randomly selected from each and analysed as per conditions

described in the extraction procedure.


21


22

�� 5HVXOWV�DQG�'LVFXVVLRQ��

�� 0DVV�VSHFWUD�RI�XQILUHG�SURSHOODQW�FRPSRQHQWV�

In order to monitor any changes between unfired propellant particles, it is vital to

initially determine the constituent compounds. This was done with GC-MS, which

allowed for the peak identification through comparison with standards and mass

spectral library matching.

The selected target compounds are listed in table 3.1, with their major ions. These

compounds were diphenylamine (DPA), N,N-Diethylcarbanilide (Ethyl centralite,

EC) and dibutyl phthalate (DBPH). Due to the fact some components are rare, and/or

are explosive in nature with associated health and safety issues, nitro-glycerine and

nitrated derivatives of DPA could not be obtained commercially. As a consequence,

analysis was concentrated on DPA, EC and DBPH.

Table 3.1: Selected target compounds (from NIST library)

Major ion data for standard compounds

Compound Major ions (m/z)

DPA 169,77

EC 120,148

DBPH 149

3.1.1 Diphenylamine (C12H11N)

Diphenylamine (which is used as a stabilizer in propellant) is classed as a secondary

aromatic amine which is a group of basic organic compounds derived from the

ammonia (NH3) group by replacing two hydrogen atoms by alkyl, aryl groups or


23

organic radicals. Amines, like ammonia, are weak bases because the unshared

electron pair of the nitrogen atom can form a coordinate bond with a proton. Amides

can be produced by reacting amines with acids anhydrides or esters. Furthermore,

amines react with acids to give salts or reaction with halogenated alkanes can occur

to form longer chains.

Many amines are not only bases but also nucleophiles that form a variety of

substituted compounds. Due to their basic chemical functionality, they are important

intermediates for chemical syntheses with substitution occurring at the nitrogen

atom.

Aromatic amines also exist, such as phenylamine and benzylamine, which dissociate

in water (some very weakly). Aromatic amines are much weaker bases than

aliphatics. The term benzyl describes the radical, ion or functional group C6H5CH2-,

derived by the methyl group of toluene losing one hydrogen atom. Phenyl on the

other hand is the term for the monovalent radical C6H5-, derived by the removal of a

hydrogen atom from a benzene ring. One of the most important aromatic amines is

aniline, a primary aromatic amine replaced by one hydrogen atom of a benzene

molecule with an amino group.

Diphenylamine or N-phenyl aniline is a highly reactive secondary aromatic amine

which undergoes electrophilic aromatic substitution (for example in the presence of

nitrogen oxides) which is heavily activated by the amino function (which is an

otho/para director) and the electron rich benzene ring.

The mass spectrum for commercially available diphenylamine is shown in figure 3.1.


24

Figure 3.1 Mass spectrum of diphenylamine

The mass spectrum of DPA is identifiable by the characteristic m/z 169 ion which is

the molecular weight of DPA. The next major ion is m/z 77 which relates to the

aromatic residue found in DPA (C6H5 = m/z 77).

Figure 3.2 Chemical structure of diphenylamine and m/z = 77 fragment ion (C6H5)

3.1.2 Ethyl centralite (C17H20N2O)

Ethyl centralite or its synonyms N,N-Diethylcarbanilide and N,N-diphenyl urea is a

white to grey crystalline powder which is commonly used as a burning modifier and

stabilizer in propellant manufacture. It serves a similar purpose in ammunition to

diphenylamine however its molecular weight is substantially larger than that of

diphenylamine. The chemical structure of ethyl centralite is presented in figure 3.3.


25

Figure 3.3: Ethyl Centralite

Figure 3.4: Mass spectrum of ethyl centralite

The mass spectrum (figure 3.4) of ethyl centralite shows a characteristic ion at m/z

268 which corresponds to the molecular ion. Again, m/z 77 ion is observed which is

indicative of the phenyl ring. The m/z ions of 148 and 120 indicate a cleaved bond

between carbon and nitrogen to form radical ions. This is illustrated in figures 3.5

and 3.6.

N

C2H5

C

O

N

C2H5

Figure 3.5: Fragmentation ions of ethyl centralite


26

N

C2H5

N

C2H5

C

O

A B

Figure 3.6: Fragment A = m/z 120 and Fragment B = m/z 148

3.1.3 Dibutyl phthalate (C16H22O4)

Dibutyl phthalate is a compound within a group called phthalate esters. Phthalate

esters exhibit similar chemical properties to each other with a general structure of the

group shown in figure 3.7.

&

&

2

2

2

2

5C

5

Figure 3.7: General structure of phthalate esters where R, R’ = CnH2n+1; n=4-15[50]

Phthalate esters are a group of plasticizers which are made by the reaction of alcohol

with phthalic anhydride which results in a stable compound. Its use in propellant is

primarily to convert NC from its natural fibrous state into a gel (treated with solvent

first which is later evaporated). Furthermore it provides flexibility to the powder

grains.

Phthalate esters not only exhibit similar chemical properties, the mass spectra for this

group of compounds is remarkably similar, with the indicative ion m/z 149

displayed. Diagnostic ions are shown in figure 3.8 which show the chemical

fragmentation of butyl phthalate esters.


27

C

C

OH

O

O

C

C

O

O

O C4H9

C

C

O

O

OR

OR‘

C

C

OH

OH

O

OC4H9

m/z = 149 m/z = 205 m/z = 222 (where R and R‘ = butyl) m/z = 223

Figure 3.8: Characteristic fragmentation ions of butyl phthalate esters [51]

As previously stated, the characterization of phthalate esters is usually relied upon

the identification of m/z 149. However, for this reason it is imperative that correct

identification of each phthalate ester occurs. In the instance of dibutyl phthalate, it is

important to consider the higher mass range ions which are usually low in abundance

and readily overlooked. Dibutyl phthalate has two indicative ions in the higher mass

region; being m/z 205 and m/z 223[50]. Figure 3.9 shows the mass spectrum of

dibutyl phthalate and its chemical structure.


28

O

O

O

O

Figure 3.9: Mass spectrum and chemical structure of dibutyl phthalate

�

�� &RQWUROOHG�6WDQGDUGV�

To gain a preliminary understanding of instrumental variation with respect to each of

the previous compounds listed, standard stock solutions of each were made and

analysed using methodology described in chapter 2.


29

3.2.1 Diphenylamine, ethyl centralite and dibutyl phthalate variation

Table 3.2 DPA, EC and DBPH standard variation

DPA EC DBPH

1 14531326 6890266 16237299

2 15203256 6933313 16767661

3 15408997 6918529 16640942

4 6914442 16798652

5 6993372 16629834

6 7055142 16418809

7 7010126 16677736

8 7042268 16643994

9 7058014 16369011

10 7008347 16577326

Average 15047860 6982382 16576126

% Variation 3% 1% 1%

Each solution was analysed as discussed in chapter 2. The results in table 3.2 show a

satisfactory variation of 1-3% for the components.


30

�� 7KH�DQDO\VLV�RI�SURSHOODQW�XVLQJ�(WK\O�$FHWDWH�DORQH�

Current methods involve the dissolution of the propellant into an organic solvent and

analysis by various techniques such as electrophoresis, HPLC or the GC-mass

spectrometer. Acetonitrile and methanol are commonly used as extraction solvents

however the toxic nature of these solvents makes them undesirable to work with. A

small scale investigation into the extraction efficiency of different solvents was

performed and ethyl acetate has been chosen for this experiment because it is has

similar solvent properties to other commonly used chemicals but with less toxicity.

From the standards preparation, optimal weights of the propellant were determined.

This was carried out by using a single point calibration and ensuring that the signals

obtained for each of the analytes DPA, EC and DBPH in the standard preparation

were not overloaded during the GC-MS analysis. From this it was determined that

50mg of propellant to 5ml of ethyl acetate would be adequate in achieving this. Since

the GC-MS methodology had been previously established by the Queensland Police

Service, chapter two explains the instrument parameters used. However, from the

standard preparations it was shown that good peak separation and shape was

occurring (see appendix).

To determine the variation caused by using ethyl acetate extraction, three random

projectiles were opened and the propellant extracted. The propellant was dissolved

using methods already discussed and triplicate samples were analysed.

Unfortunately, samples cannot be analysed simultaneously. The second sample

cannot be injected until the chromatography of the first sample is complete and the

injection of the third sample is delayed even longer. Hence there is an unavoidable

time delay between the analysis of each sample. Any changes which occur during

this time delay could clearly influence the outcome of the analysis.

From the results shown below in table 3.3, a significant variation in DPA response

can be seen. There are many possible reasons for this variation. For example, the

variation could be due to the variation in propellant composition, decomposition or


31

reactions occurring in solution. The later is a likely cause as the literature contains

several reports on the nitrated derivatives of gun shot residue. This will be discussed

later.

Table 3.3 Variation in peak area of DPA between three random propellant samples and

variation observed between the three samples

Sample one 1048904

Sample one 979882 Average 950110

Sample one 821543 % Variation 12%

Standard deviation 125511

Sample two 950589 Average 858474

Sample two 824614 Average 832339 % Variation 15%

Sample two 721814 % Variation 14%

Sample three 919557 Average 792973

Sample three 794653 % Variation 16%

Sample three 664709

Diphenylamine degradation

Sample 1

Sample 1

Sample 1

Sample 2

Sample 2

Sample 2

Sample 3

Sample 3

Sample 3

600000

700000

800000

900000

1000000

1100000

1200000

0 50 100 150 200 250 300 350 400

Time (mins)

Peak

Are

a

Figure 3.10: Diphenylamine degradation over time

It can be seen from figure 3.10 that the amount of diphenylamine detected drops

significantly over the 360 minute analysis time. When each individual sample is

observed more closely, the true effect of degradation can be more easily seen. This is

illustrated in figures 3.11 - 3.13.


32

The variation levels of over 16% are evident in the figures, indicating a great

degradation of diphenylamine over the course of analysis. Variation due to

instrumentation has been established at approximately 6%, which is a lot less then

the actual variation observed in this study. Another 10% variation therefore has been

likely observed in the propellant sample.

Sample 1: Diphenylamine degradation

Sample 1

Sample 1

Sample 1

600000

700000

800000

900000

1000000

1100000

1200000

0 50 100 150 200 250 300

Time (mins)

Peak

Are

a

Figure 3.11: Sample 1 - diphenylamine degradation


33


Sample 2

Sample 2

Sample 2

650000

700000

750000

800000

850000

900000

950000

1000000

1050000

1100000

0 50 100 150 200 250 300 350

Time (mins)

Peak

Are

a



Sample 3

Sample 3

Sample 3

450000

550000

650000

750000

850000

950000

1050000

0 50 100 150 200 250 300 350 400

Time (mins)

Peak

Are

a



34

It has been extensively reported in the literature that decomposition of diphenylamine

occurs in nitrocellulose based propellants. Nitrocellulose and nitro-glycerine (both

commonly found in 0.22 calibre double based smokeless powders) break down to

form nitrogen oxides which are highly reactive. If these decomposition products are

not removed from the propellant, they serve as a catalyst for further reaction and the

shelf life of propellant samples can be shortened. Furthermore, self-ignition of the

propellants is possible, thus making this situation highly dangerous.

The downward trend of the amount of diphenylamine detected could therefore be

attributed to the creation of nitrated diphenylamine decomposition products.

2-nitro-DPA

Sample 1, 270

Sample 1, 0

Sample 1, 135

Sample 2, 315

Sample 2, 180

Sample 2, 45

Sample 3, 360

Sample 3, 225

Sample 3, 90

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

26000

28000

30000

0 50 100 150 200 250 300 350 400

Time (mins)

Pe

ak

are

a

Figure 3.14: 2-nitro-diphenylamine amounts detected (three random samples) – Extrapolated to

time zero to give appreciation of initial amounts of 2-nitro-DPA in each sample

This is confirmed in figure 3.14 which demonstrates the presence of 2-nitro-

diphenylamine in the propellant samples. Each of the three samples show an increase

in the amount of nitrated derivative detected over time. As the samples remain in

solution on the auto sampler for extended periods of time, reactions occur resulting

in the increased concentration of this nitrated derivative. The results shown in figure

3.14 complement the results shown in figure 3.10; since as the amount of

diphenylamine decreases the concentration of nitrated diphenylamine derivative


35

increases. Interestingly, since the rate of increase appears to be linear, extrapolation

to time zero provides an estimate of 2-nitro-DPA present initially in each cartridge.

The results are consistent with the initial DPA concentrations. Sample one (with the

largest initial DPA response) also gave the largest 2-nitro-DPA response. This is also

observed with samples two and three.

Furthermore, it is interesting to observe that the three random samples taken for this

experiment, yield different amounts of not only diphenylamine but also its nitrated

derivative. The rise in the mono-nitrated derivative can be explained by the fact that

by 360 minutes, DPA has had the longest time to react with any breakdown products

of nitrocellulose. However, it should be pointed out that a variation in levels of

diphenylamine could be attributed to differing amounts of diphenylamine in each

individual projectile. This proposal will be explored further later.

For Sample one DPA concentration fell by 28% in 270 minutes while 2-nitro-DPA

increased by 26% during the same time. The equivalent numbers for sample 2 were

32% and 22% and for sample three, 38% and 25%.

The production of nitrated derivates can be rationalized as follows: the breakdown of

nitrocellulose yields NO2 radicals[10,11,13-17,30,32]. In the presence of

diphenylamine, N-nitroso-diphenylamine (N-NO-DPA), a highly reactive weak

stabilizer nitrosamine, is produced. Moriarty et al [16] investigated the role of N-

nitroso-diphenylamine as a stabilizer in cellulose matrices. In the presence of NO2,

N-nitroso-DPA can react to give 2-nitro-DPA and 4-nitro-DPA + NO (nitric oxide).

In the presence of oxygen, nitric oxide will be converted into nitrogen dioxide again,

and hence the cycle will continue until complete nitration occurs to give 4,4-diNO2-

DPA, 2,2-diNO2-DPA, 2,4-diNO2DPA or other derivatives. The mechanisms for

these reactions can be seen below in figure 3.15.


36

Figure 3.15: Mechanisms of N-Nitroso-DPA in the presence of NO2 and O2 [16]

It is important to note however that the degradation mechanisms of nitrocellulose are

still not definitely known, nor exactly how the nitration of the diphenylamine occurs.

The above mechanism is one proposed reaction sequence to explain the

phenomenon.

Although, Lussier et al[14] studied chemical reactions of diphenylamine with

nitrogen dioxide and report that diphenylamine does react with NO2 radicals to give

N-nitroso-DPA. Interestingly, as more NO2 was added to diphenylamine, a

distinctive trend was observed. This is illustrated in figure 3.16.

halla



37

Figure 3.16: Lussier and Gagnon [14]: Concentration of DPA and its derivatives as a function of

added nitrogen dioxide

As the concentration of NO2 increases, the level of DPA decreases, probably caused

by nitration. This is supported by the fact that the amount of N-nitroso-DPA

increases at the same time. Interestingly, the amount of N-nitroso-DPA falls further

as the other nitrated derivatives begin to increase. It could be proposed that N-

nitroso-DPA is responsible for the further nitration of diphenylamine or its mono-

nitrated derivatives to give fully nitrated derivates (2 or 4-NO2-N-NO-DPA).

While these theories have been put forward, the loss of diphenylamine could simply

be the result of nitrocellulose matrix and diphenylamine interacting to form a

compound not amendable to extraction techniques.

The reasons for the loss of diphenylamine and consequent detection of mono-nitrated

derivates are therefore supported by the literature. However, as the experiments were

carried out in an oxygen rich environment, oxygen may function as a catalyst for the

reactions.

halla



38

While the heavily saturated nitrated derivatives such as 2 and 4-NO2-N-NO-DPA

were not observed, this could be due to thermal decomposition in the GC inlet or to

insufficient time in the methodology for further reactions to occur.

To support the theory that oxygen, storage and light play a role in the decomposition

of the propellant, an opened cartridge case was placed in a screw capped vial and left

for two weeks in low light and adequate oxygen before analysis. In order to minimize

variation, the same box of ammunition previously studied was used. The results can

be seen in figure 3.17.

Effect of storage on Diphenylamine amounts detected

Sample 1

Sample 1

Sample 2

Sample 2

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000

Stored Fresh

Average response (triplicate)

Peak

Are

a

Figure 3.17: Effect of storage on diphenylamine concentration (sample one and two)


39

Sample 1: The effect of storage on Diphenylamine

Fresh

Fresh

Fresh

Stored

Stored

Stored

0

200000

400000

600000

800000

1000000

1200000

0 20 40 60 80 100 120 140 160 180 200

Time (minutes)

Pea

k A

rea

Figure 3.18: Sample 1 - Effect of storage on diphenylamine (triplicate)

Figure 3.17 shows the effect of leaving the propellant in an oxygen rich environment.

Over the course of two weeks, the amount of diphenylamine in the samples has

decreased quite significantly. Again, the downward trend for the fresh and stored

samples could now be attributed to the compounds being in solution and reactions

occurring via mechanisms previously discussed. Figure 3.18 allows a closer

examination of sample one. An average decrease of 21% is observed which supports

previous observations which indicated that leaving diphenylamine in solution over a

period of time is not recommended.

Observation of the levels of nitrated derivates further explains these reactions.


40

Sample 1: The effect of storage on 2-nitro-diphenylamine amounts detected

270 min

135 min

0 min

0

5000

10000

15000

20000

25000

30000

Time (minutes)

Pe

ak

Are

a

fresh 20078 23528 27276

stored 11111 18336 20276

0 135 270

Figure 3.19: Sample 1 - The effect of storage on 2- nitro-diphenylamine (analysed three times)

Figure 3.19, shows a significant increase of nitrated derivates with time. Figure 3.19

shows a triplicate analysis of sample one and the trends previously observed are

evident here also. Bergens et al[10,11] proposed that after day 20 of propellant

storage, mono nitrated derivatives are at their maximum which coincides with DPA

being at its lowest. This could explain why the amounts of 2-nitro-DPA in stored

samples are relatively high. An increase of 45% was observed over the period of

analysis (180 minutes). This indicates that the stored samples are significantly more

reactive than the freshly analysed samples. The freshly prepared samples showed an

increase of 26% over the period of analysis (180 minutes). Whilst it is clear that the

stored samples actually yielded lower detectable concentrations of nitrated DPA

derivatives, this could be due to the fact that the diphenylamine concentrations

decreased in the samples exposed to oxygen for extended periods of time. Or

possibly, it could be due to further reactions to give di-NO2 species. To fully

understand the mechanisms that differ between the fresh and opened samples, a more

comprehensive study would need to be done.


41

In order to establish the effect of leaving propellant in solution the same samples that

were stored in low light were left in solution for one week. Figure 3.20 illustrates the

effect this had on diphenylamine concentration.

The effect of leaving propellant in solution for one week on diphenylamine

Sample 1

Sample 1

Sample 2

Sample 2

0

5000

10000

15000

20000

25000

30000

Stored Solution

Sample (analysis average)

Peak

Are

a

Figure 3.20: Sample one and two analysed each three times (average): comparison between

stored samples and samples left in solution for one week.

It is evident that leaving propellant in solution affects the concentration of

diphenylamine, and again reinforces the consequences of leaving the samples in

solution for long periods of time.

For sample one DPA concentration fell by 28% in 270 minutes. For sample two in

the same time, DPA fell by 15%.

The variation in concentrations of DPA between sample one and two is further

suggests that individual rounds of ammunition may contain differing concentrations

of the main constituents. This will be investigated further later. However, from the

results above, it is clear that leaving propellant samples in solution for extended

periods of time has detrimental effects on the quantifiable amounts of

diphenylamine. As the scope of the project was to ‘match’ batches of ammunition,


42

the fact that diphenylamine is reactive and unstable may suggest that this is not

possible.

A solution to the phenomenon would be to extract the propellant at the time of the

analysis (see later).

Furthermore, the concentration of the mono nitrated derivate (figure 3.21) also

suffers a 20% reduction in levels.

The effect of leaving propellant in solution over one week on 2-nitro DPA

Sample 1

Sample 1

Sample 2

Sample 2

0

5000

10000

15000

20000

25000

30000

Stored Solution

Sample (analysis average)

Peak

Are

a

Figure 3.21: The effect of leaving propellant in solution over one week (2-nitro-DPA average –

each sample analysed three times)

For sample one 2-nitro-DPA concentration fell by 27% and sample two fell by 13%

in the same time.

It has been demonstrated that the use of ethyl acetate as a solvent is adequate to

dissolve the propellant, however, leaving propellant in solution in the auto sampler

and the removing of the propellant from its cartridge case all contribute to a

significant variation in amounts of diphenylamine and its mono nitrated derivatives.

The degree of variation observed compromises the aim of matching a cartridge case


43

found at a scene to a box of ammunition. It appears that once the propellant is

exposed to oxygen or placed in solution, reactions degrade the propellant and make it

more difficult to quantify the amount of compounds present. Especially when left it

solution, the reaction with free nitrogen oxides present from the breakdown of

nitrocellulose, make the task of discriminating or matching propellant samples

almost impossible. To alleviate this situation, it is proposed that an extraction

technique to remove the nitrocellulose matrix from the sample be developed. This

would eliminate the source of the free nitrogen oxides.


44

�� 5HPRYDO�RI�WKH�QLWURFHOOXORVH�FRPSRQHQW�RI�SURSHOODQW�XVLQJ�HWK\O�DFHWDWH�DQG�GLFKORURPHWKDQH��

Optimizing the extraction procedure that will help minimize the effect of free

nitrogen dioxides in solution is of importance to the study of unfired propellant.

Otherwise the variations in the levels of DPA have been shown to be unacceptable.

The extraction technique used by Mathis et al[36] used methylene chloride as the

propellant solvent. A known mass of propellant was dissolved in methylene chloride

and an aliquot taken. This aliquot was dried with nitrogen gas and the samples

reconstituted in methanol. It was claimed that by doing this, nitro-glycerine and

nitrocellulose would remain insoluble and be removed as a source for further

nitration of diphenylamine.

Whilst the study made no attempt to establish whether discriminating or matching

propellants from the same case could be achieved, the benefits of removing the

nitrocellulose matrix are clear.

Based on this observation, samples were dissolved in ethyl acetate (EtAc) as before.

However, an aliquot was transferred to a vial and evaporated to dryness with an inert

gas (nitrogen). A globular mixture was left behind which was not analysed. The

sample was then reconstituted in dichloromethane (CH2Cl2) and left to stand for a

period of time to ensure that the globular nitrocellulose was properly removed. The

reconstituted sample was then analysed using parameters previously discussed.

Triplicates of three random samples were analysed. Results are shown in figure 3.22.


45

Ethyl acetate/dichloromethane procedure (DPA detected)

sample 1

sample 1

sample 1

sample 2

sample 2

sample 2

sample 3

sample 3

sample 3

600000

700000

800000

900000

1000000

1100000

1200000

1300000

1400000

0 50 100 150 200 250 300 350 400

Time (minutes)

Peak

Are

a

sample 1

sample 2

sample 3

Figure 3.22: Diphenylamine response (EtAc/Ch2Cl2 procedure)

It can be seen that a downward trend is still observed. This could be an indication

that not all of nitrocellulose could be completely removed when reconstituted in

dichloromethane. As a consequence, free nitrogen oxides could still be present in

solution, albeit at a lower concentration than previously. To establish the effect of the

EtAc/CH2Cl2 procedure, it must be compared to the previous dissolution method of

using only ethyl acetate.


46

Comparison between ethy acetate alone and ethyl acetate/dichloromethane procedures (DPA)

EtAc/CH2Cl2, sample 3

EtAc/CH2Cl2, sample 2EtAc/CH2Cl2, sample 1

EtAc, sample 3

EtAc, sample 2

EtAc, sample 1

0

200000

400000

600000

800000

1000000

1200000

1400000

Sample average: each analysed three times

Pe

ak

Are

a

EtAc/CH2Cl2 1162287 1130223 1022974

EtAc 973017 866383 736022

sample 1 sample 2 sample 3

Figure 3.23: Comparison between EtAc alone and EtAc/CH2Cl2 on DPA (average)

When the EtAc/CH2Cl2 procedure is compared to using ethyl acetate alone, a clear

difference is observed.

For sample one DPA concentration fell by 16% between the combined EtAC/CH2Cl2

procedure and using EtAc alone. For sample two and three, a decrease of 23% and

28% respectively was observed.

The variation between samples is further evidence that the samples should not be left

in solution for extended periods of time. Sample three had the greatest variation of

diphenylamine concentration since the time prior to analysis was longer.

Interestingly, the differences in DPA yield between the two procedures revealed that

the EtAc/CH2Cl2 procedure had an overall variation of 12% whereas the ethyl acetate

alone method revealed an overall difference of 24%. This is a significant difference

between the two methods; and it indicates that the EtAc/CH2Cl2 procedure is

preferred.


47

As previously established, it is the breakdown of nitrocellulose that gives the free

nitrogen oxides responsible for the nitration of diphenylamine, thus reducing the

possibility of matching or discriminating propellant based on the diphenylamine

levels. As shown in figure 3.23, while it is evident that diphenylamine is reacting

with nitrogen oxides and thus, yielding the downward trend of diphenylamine

amounts, the amount of diphenylamine degradation appears to have reduced. To

confirm this, the efficiency of this extraction technique was investigated by

examining the amount of mono-nitrated derivatives that were produced.

Comparison between ethyl acetate alone and ethyl acetate/dichlormethane procedures

(2-nitro DPA)



EtAc/CH2Cl2, sample 1 EtAc, sample 3

EtAc, sample 2

EtAc, sample 1

0

5000

10000

15000

20000

25000

Sample (average)

Pea

k a

rea

EtAc/CH2Cl2 19800 17718 15641

EtAc 23627 21702 19862


Figure 3.24: Comparison of EtAc alone and EtAc/CH2Cl2 procedures - 2-nitro-dpa (average:

each sample analysed three times)

Figure 3.24, shows the ethyl acetate alone procedure produces significantly more

nitrated derivatives of DPA, than the EtAc/CH2Cl2 procedure. The amount of nitrated

derivatives formed in sample 1, was reduced by 19% when using the EtAc/CH2Cl2

procedure; sample 2 by 22% and sample 3 by 27%. This suggest that the

EtAc/CH2Cl2 procedure is desirable when analysing propellant samples as it has

assisted in slowing or diminishing the amount of nitrated derivatives formed over

long periods of time.


48

To gain a better illustration exactly what is happening, a more thorough analysis of

sample one is shown below.

Sample 1: Comparison between EtAc alone and EtAc/CH2Cl2 procedures (2-nitro DPA)

EtAc/CH2Cl2, 270

EtAc/CH2Cl2, 135EtAc/CH2Cl2, 0

EtAc, 270

EtAc, 135

EtAc, 0

0

5000

10000

15000

20000

25000

30000

Time (minutes)

Pea

k A

rea

EtAc/CH2Cl2 20084 21319 17998

EtAc 20078 23528 27276

0 135 270

Figure 3.25: 2-nitro-dpa levels - sample 1: comparison between EtAc alone and EtAc/CH2Cl2

procedures

From figure 3.25, the differences in levels of 2-nitro-DPA are clear. The

EtAc/CH2Cl2 technique has slowed the production of 2-nitro-DPA. Compared with

the EtAc alone procedure which appears to produce higher amounts of 2-nitro-dpa as

the analysis progresses (EtAc alone procedure resulted in an increase in production

of 2-nitro-DPA of 27% compared to the EtAc/CH2Cl2 procedure which saw a

decrease in 2-nitro-DPA production of 12%). It is suggested that a reason for this

phenomenon is that when the propellant is in solution with ethyl acetate, the

concentration of free nitrogen oxides is much higher than when extracted using

dichloromethane. The higher concentration of free nitrogen oxides present in solution

could be responsible for the greater amount of nitration that is evident as the analysis

progresses. Conversely, when the propellant is in solution with dichloromethane, the


49

concentration of nitrogen oxides is much lower as it was proposed that the

EtAC/CH2Cl2 extraction technique should remove the source of these oxides. This

would indicate that 2-nitro-DPA is less likely to be produced.

It has been shown that the combined EtAc/CH2Cl2 technique has provided an

environment less susceptible to nitrocellulose breakdown, thus reducing the amount

of mono-nitrated derivatives being formed in solution. This is of importance as the

degree of nitration can interfere with observed diphenylamine and consequently, the

levels.

While attention has been concentrated on diphenylamine, it is important to establish

whether the EtAc/CH2Cl2 technique was suitable for the other components of unfired

propellant; ethyl centralite and dibutyl phthalate. Firstly, a comparative diagram is

shown in figure 3.26 which indicates that while similar amounts of ethyl centralite

were detected, a higher level of ethyl centralite was observed using the EtAc/CH2Cl2

technique. This provides further evidence to support the proposal that the

EtAc/CH2Cl2 technique will be a better method for unfired propellant analysis.


50

Comparison between EtAc alone and EtAc/CH2Cl2 procedures (Ethyl Centralite)

EtAc/CH2Cl2EtAc/CH2Cl2EtAc/CH2Cl2

EtAcEtAcEtAc

0

1000000

2000000

3000000

4000000

5000000

6000000

Sample (average)

Pe

ak

Are

a

EtAc/CH2Cl2 5511039 5511129 5488933

EtAc 5173739 5056856 4972894


Figure 3.26: Comparison between EtAc alone and EtAc/CH2Cl2 procedures (ethyl centralite

average)

The degree of variation of EC between the two methodologies is not as great as for

DPA. For sample one, the use of the extraction procedure increased the yield of EC

by 6%. For sample two, an increase of 8% and for sample 3 an increase of 9%. This

is an overall average of 8% increase. The degree of variation in the concentrations of

EC between samples could be attributed to varying amounts of EC within the

propellant.

Furthermore, as shown in figure 3.27 the effect of reconstituting dibutyl phthalate in

dichloromethane as opposed to ethyl acetate, seems to have no significant bearing on

the amount detected. This compound did however show a decrease in level for the

three samples when using the extraction procedure (sample 1: -6%, sample 2: -2%

and sample 3: -1%). Whilst the decrease cannot be fully explained, it is likely that

solubility is the major cause for this situation.


51

Comparison between Ethyl acetate alone and ethyl acetate/dichlormethane procedures

(dibutyl phthalate)

EtAc

EtAcEtAcEtAc/CH2Cl2

EtAc/CH2Cl2EtAc/CH2Cl2

0

200000

400000

600000

800000

1000000

1200000

1400000

Sample (average)

Pe

ak A

rea

EtAc/CH2Cl2 1238280 1230035 1189287

EtAc 1315107 1255621 1204949


Figure 3.27: Dibutyl phthalate – comparison between EtAc alone and EtAc/CH2Cl2 procedures

In contrast to the results reported previously, Bergens et al[10,11] used

dichloromethane to extract the analytes and they compared this new solvent to

acetonitrile. No significant differences in the level of diphenylamine were detected

between the two solvents. They were unable to explain the losses of diphenylamine

over time, and suggested that the losses of diphenylamine using acetonitrile were due

to poor extraction techniques. It is more likely however, that while the extraction

technique has removed most of the nitrocellulose and nitro-glycerine matrix, some of

it may have been left behind, leaving a possible source of free nitrogen oxides once

more.

In this project, a higher level of diphenylamine was detected. The discrepancy

between this result and that of Bergens et al[10,11] could be explained by the

following reasons; (1) the propellant in this study was fresher or closer to the time of

manufacture and had less time to decompose inside the cartridge case. (2) Their

extraction technique did not involve evaporation and so the solution was more

susceptible to possible nitration. (3) Perhaps the interaction between diphenylamine


52

and nitrocellulose produces a product that may be susceptible to extraction

depending on the amount of nitrocellulose or diphenylamine concentrations in the

propellant.

The act of reconstituting the mixture in dichloromethane appears to have a positive

effect not only on the level of the main constituents of unfired propellant, but it also

slows down the effect of nitration by removing most of the nitrocellulose matrix. As

a consequence, it is desirable to use this method for the analysis of unfired propellant

and to determine whether matching or discriminating propellant is possible.

Before exploring this it is necessary to establish whether the propellant within a

single batch is consistent.


53

�� &RQVLVWHQF\�RI�SURSHOODQW�FRPSRVLWLRQ�IURP�D�VLQJOH�ER[�EDWFK�RI�DPPXQLWLRQ�

Establishing the consistency of propellant composition from a single batch of

ammunition is of great importance to the success of the project. This clearly

influences the possibility for matching or discriminating propellant.

Statistics is needed to establish a population size for sampling. A population analysis

by definition will include samples from a global population; however, in the case of

ammunition studies it would be impossible to sample every 0.22 ammunition type

available. For this reason, a sampling size of ten bullets was deemed to be suitable as

it is shown statistically to represent 0.989 of the population.

Table 3.4: Relationship between sample size and population size

Relationship between sample size and population size

sample size n population size N sampling fraction ¥{N-n)/N}

10 50 0.9990

10 500 0.9899

10 5000 0.8944

Using the EtAc/CH2Cl2 technique previously developed, investigation of the

chemical constituents from ten (10) random propellant samples was carried out.

Each propellant sample was weighed to establish the variation in the amount used in

a particular brand of ammunition. Interestingly, from the ten random samples

analysed, a variation in mass was observed. The masses of the ten samples can be

viewed in table 3.5.

Table 3.5: Masses from ten random samples from one box of ammunition

Masses from ten random samples from one box of ammunition (mg)

Sample A

Sample B

Sample C

Sample D

Sample E

Sample F

Sample G

Sample H

Sample I

Sample J

94.9 100.2 96.5 96.2 96.3 95.9 96.8 99.9 96.7 96.1


54

The average across the ten samples is 96.9mg with a standard deviation of 1.7 and a

percentage variation of 1.7%, which is not significantly high.

Ammunition relies on a particular barrel pressure of the cartridge to reduce any

possibility of back-fire or loss of velocity of the ammunition once it has left the

barrel of the weapon. In order to maintain quality control of the ammunition, it is the

barrel pressure of the ammunition that is tested, not the exact weight of the

propellant. Therefore, this could include changing the weight of the propellant

slightly in order to maintain the ammunition performance. Barrel pressure should lie

within certain predetermined specifications within any given batch. It is unclear from

the manufactures information whether the same material is used for a single batch.

However, this work showed a variation in the amount of propellant within one batch.

Management of Winchester, Geelong stated that a batch of ammunition referred to

all boxes made on the same day by the same machine. It is also interesting to note

that the propellant (while traceable) was left to stand in the open air for hours even

days at a time. This would undoubtedly have an effect on the degradation of the main

constituents, particularly diphenylamine. Furthermore, Winchester do not

manufacture their own propellant, rather it is outsourced to other companies from

overseas. All these issues indicate the possibility of the propellant being inconsistent

in both amount and composition.


55

DPA: Amounts detected from ten (10) random propellant samples

0

50000

100000

150000

200000

250000

Sample No.

Pea

k a

rea

DPA 200936 155303 109123 105767 83675 68655 84550 51156 52088 41490

A B C D E F G H I J

Figure 3.28: Levels of diphenylamine of ten (10) random samples of propellant from the one box

of ammunition

DBPH: Amounts detected from ten (10) random propellant samples

0

50000

100000

150000

200000

250000

Sample No.

Pea

k a

rea

DBPH 205462 143263 148343 128776 126006 111910 111315 121002 90854 97238

A B C D E F G H I J

Figure 3.29: Levels of dibutyl phthalate detected of ten (10) random samples of propellant from

the one box of ammunition


56

It can be seen from figures 3.28 and 3.29 that a large variation is observed in the

concentration of each constituent (variation equated to 53% for DPA). It should be

noted that all analyses were performed under the same conditions as previously

discussed, and to help eliminate the effect of propellant remaining in solution and

exposed to oxygen, all samples were made freshly one at a time and analysed

immediately. The instrument was tuned at the start of the experiment and found to

be working satisfactorily. It can therefore be assumed that the instrument was

correctly functioning at the time of each sample analysis.

MacChrehan et al[52,53] established a propellant (p) to stabilizer (s) ratio as a

parameter to explain any variation. Ammunition relies on nitro-cellulose as its

explosive source. While a method was established to detect and quantify nitro-

glycerine in this project, nitro-glycerine was often not analysed as it was assumed

that all ammunition was double based. This means testing for nitro-glycerine was not

carried out in all experiments. However, other ratios could be used to explain

variations that may be evident. By comparing ethyl centralite, diphenylamine and

dibutyl phthalate, a different perspective can be obtained for the differences between

the samples. The results are shown in table 3.6.

Table 3.6: Ratios (peak area) of main constituents from one box of ammunition

Ratio A B C D E F G H I J

DPA/EC 27.6 46.2 32.6 32.6 27.6 30.7 33.4 22.0 36.7 24.8

EC/DBPH 0.035 0.023 0.022 0.025 0.024 0.020 0.022 0.019 0.016 0.017

DPA/DBPH 0.97 1.08 0.74 0.82 0.66 0.61 0.76 0.42 0.57 0.43

Average Standard Deviation

% Variation

DPA/EC 31.5 6.79 21.5

EC/DBPH 0.023 0.0055 24.3

DPA/DBPH 0.71 0.22 30.5

It can be seen from table 3.6 that the variation between the ten random samples is

significant and indicates that the propellant is not consistent in composition. It would


57

be expected that the variation in the ratios containing diphenylamine would be high

for reasons previously discussed, however, when ethyl centralite and dibutyl

phthalate were compared, the variation is still around 25%.

In a situation where only three major components (DPA, EC and DBPH) are found in

the propellant it is questionable whether the use of ratios will successfully

discriminate between propellant samples. Considering that diphenylamine is reactive

it is appropriate to question whether this component should in fact be used in a ratio

to explain variation. This only leaves two components (EC and DBPH) left for

comparison and determining that any two samples are from the same source or are in

fact different may be difficult.

It should be noted however that only one brand of ammunition has been tested and to

establish whether this is true for all ammunition types, a more comprehensive study

would need to be carried out. Not only are there different calibres of ammunition, but

different brands, types and batches. Furthermore, any discrepancies discovered could

be a result of the storage of the propellant before being placed into the cartridge case.

As the manufacturers of the propellant exercise proprietary over their details of the

propellant it is difficult to establish the exact nature and ingredients of the propellant

before Winchester use this to engineer their products.

The variation is over 30% (ratio) and 50% (peak area) which is well beyond

instrumental variation of 1-3% or the EtAc/CH2Cl2 procedure variation of 9%. This

indicates that the source of the variation is the propellant itself, not the conditions

under which it was analysed.

To further establish whether the propellant composition variation is coming from the

propellant itself or from other sources (e.g. oxygen), an experiment was designed in

which the propellant was manipulated in an inert atmosphere.


58

�� 7KH�HIIHFWV�RI�H[FOXGLQJ�R[\JHQ�

The effect of oxygen on the degradation of diphenylamine has been widely accepted

[10-12,14,16,22,30,33,35]. It has been proposed that oxygen provides a catalytic

effect, resulting in the nitrated derivative by-products. Therefore, it could help to

perform all manipulations under an inert atmosphere.

Five (5) random samples were chosen from the same batch of ammunition and

prepared as previously. However, all manipulations were done in a nitrogen filled

glove box. The glove box was allowed to flush for 24 hours before use to eliminate

all traces of oxygen. Samples were again dissolved one at a time and analysed

immediately. The results are tabulated in figure 3.30.

Inert gas procedure: Main constituents

DPADPA DPA DPA

DPAEC EC EC EC EC

DBPH

DBPH DBPH

DBPH

DBPH

0

200000

400000

600000

800000

1000000

1200000

1400000

Sample No.

Peak

Are

a

DPA 107617 155900 173591 156886 125608

EC 86859 80196 90023 90767 87273

DBPH 1156875 1062508 1079445 1181054 1126170

A B C D E

Figure 3.30 Inert gas procedure consequences on the main constituents of unfired propellant

particles

It is evident from figure 3.30 that variation still exists between the five random

samples. DPA shows a percentage variation of 19%. EC displays a percentage

variation of 5% and DBPH a percentage variation of 4%. This not only indicates that

performing the analysis under an inert atmosphere dramatically affects the degree of


59

variation between samples, but it reinforces the impact that storage has on the

ammunition itself. However, the results could also indicate the actual degree of

variation between propellant samples within a box of ammunition. Whilst the

variation for EC and DBPH is respectable at less than 5%, the degree of variation for

DPA at 18% is too high for batch comparison to be accurately performed.

The variation between samples in an oxygenated environment was as high as 25-30%

for DPA. The EtAc/CH2Cl2 extraction technique showed a variation of

approximately 12% for DPA and the inert gas procedure showed a variation of

approximately 18%. This indicates a real variation in DPA levels which is

independent to methodology.

To further explore the variation of the propellant make-up, it may be beneficial to

examine the degree of variation for dibutyl phthalate, a plasticizer and therefore a

more stable compound. Figure 3.30, shows the variation of propellant composition.

Whilst it was previously suggested that storage of the propellant plays a significant

role in accelerated decomposition of the nitrocellulose, the levels of dibutyl phthalate

should not be affected by storage and so any variation suggests an inconsistency in

propellant composition.


60

Inert gas procedure: DBPH (5 random propellant samples)

0

200000

400000

600000

800000

1000000

1200000

Sample No.

Pe

ak A

rea

DBPH 1156875 1062508 1079445 1181054 1126170

A B C D E

Figure 3.31: Inert gas procedure (dibutyl phthalate)

The variation of DBPH in an oxygenated environment was 4%. The variation of

DBPH observed here is difficult to explain.

It is shown in figures 3.30 and 3.31 that no downward trend has occurred using the

inert gas procedure. The downward trend was attributed to the length of time each

sample waited to be analysed and this direct correlation with diphenylamine in

solution. However it may be possible to leave samples in the auto-sampler for long

periods of time under a nitrogen atmosphere provided the seal has not been

perforated. This possibility was explored further.

Another five (5) random samples were dissolved and manipulated in the inert

atmosphere. When the samples were left in the auto sampler, the nitrogen filled GC

vial has prevented any further reaction that would have occurred if oxygen was

present.


61

The effects of leaving propellant in solution on five (5) random samples

dpa

dpa

dpa dpa dpa

ec ec ec ec ec

dbph

dbphdbph

dbph

dbph

0

50000

100000

150000

200000

250000

300000

350000

Sample No.

Pe

ak

Are

a

dpa 72050 87269 101338 97371 94718

ec 17943 23275 22465 25304 27766

dbph 213869 269585 263629 289639 314656

sample f sample g sample h sample i sample j

Figure 3.32: The effects of leaving propellant in solution under an inert atmosphere

In this series of experiments the levels of concentration variation of each component

were in the vicinity of 13% (DPA 13%, EC 15% and DBPH 14%). The results

further support the idea that the concentration of each constituent is different within a

batch of ammunition. In the presence of oxygen, the variation observed was DPA

18%, EC 5% and DBPH 4%. However, the main point is that the concentration of the

constituents is scattered and not in a downward trend shown when dissolution in

ethyl acetate alone was used. It appears that with the lack of oxygen, no catalytic

effect is present and a true representation of the constituent concentrations is

observed.

While this may be the case, the importance of leaving samples in the auto sampler is

evident. In a busy laboratory, time is important and bulk sample preparation is more

efficient. While the use of inert gas glove boxes is appropriate in studying the origin

of variation, it could also be incorporated into regular forensic testing.

The effect of leaving the sample in solution is further explored by re-analysis of

previous samples A-D 24 hours later. A new screw capped vial lid with septa was the


62

only change that occurred to these samples and the results are shown as below in

figure 3.33.

Re-analysis 24 hours later - the effect of time on Diphenylamine

0

20000

40000

60000

80000

100000

120000

140000

160000

180000

200000

A B C D

Sample No.

Peak

Are

a

DPA

DPA (+24 Hours)

Re-analysis 24 hours later - the effect of time on Ethyl Centralite

70000

75000

80000

85000

90000

95000

A B C D

Sample No.

Peak

Are

a

EC

EC (+24 Hours)


63

Re-analysis 24 hours later - the effect of time on Dibutyl phthalate

950000

1000000

1050000

1100000

1150000

1200000

1250000

A B C D

Sample No.

Peak

Are

a

DBPH

DBPH (+24 Hours)

Figures 3.33: Re-analysis of samples A-D 24 hours later (individually separated for visual

clarity)

As shown in figures 3.33 the changes are significantly different from leaving the

solution in an oxygen fuelled environment. DPA concentration has changed by 15%

over 24 hours, EC by 1% and DBPH by 1%. Interestingly, in the case of EC and

DBPH, an increase in the amount detected of these additives has been observed. This

differs from the oxygen rich environment where a 30% variation for DPA was

observed over 360 minutes. It is clear that the effect of manipulating samples in an

inert atmosphere has slowed down the catalysis by oxygen, and thus the amount of

the constituents has not altered greatly. In a real life situation, the sample at a crime

scene would have been exposed to oxygen until police or crime scene examiners can

collect the evidence. Since oxygen plays a significant and detrimental effect on

quantifying diphenylamine, the possibility of matching any crime scene evidence to a

box or batch of ammunition would be almost impossible. To overcome this it may be

possible to develop inert atmosphere sampling bags to minimise the effects that

oxygen has on the propellant. It has so far been shown that the propellant is

susceptible to chemical reactions both in solution and on storage. Furthermore, the

total mass of the charge within individual cartridges also varies. This suggests that


64

the possibility of matching a sample to its original box is unlikely. Nevertheless it

may be possible to match ammunition to a particular brand since different

manufacturers may have their own unique propellant composition.


65

�� 7\SH�GHWHUPLQDWLRQ�RI�:LQFKHVWHU�$PPXQLWLRQ�

Matching a projectile to a batch of ammunition is not possible however, it may be

possible to determine the type or brand of ammunition. To explore this suggestion, a

small study was carried out using six different types of ammunition selected from the

Winchester brand with two projectiles from each type analysed. Ammunition types

included Long rifle (LR), Hollow Point (HP) and High velocity (HV) varieties.

3.7.1 Winchester Laser LR HP 2DRM41

This type of ammunition was found to contain the following constituents; Diethyl

phthalate (DEPH), DPA, EC, DBPH and 2-nitro-DPA. The concentration of DEPH

was found to vary by 77% between the two samples from this batch. This is a

significant variation. DPA was found to have a variation of 2%, EC of 13%, DBPH

of 4% and 2-nitro-DPA of 12%. This is shown in figure 3.34.

Winchester Laser Long Rifle Hollow Point D2RM41

0 0 77941113537

12090531

69363

5839487

399766

6050093

45213925910

12367704

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

2,4 DNT DEPH DPA EC DBPH 2-Nitro DPA

Component

Pea

k A

rea

Laser 1

Laser 2

Figure 3.34: Winchester Laser LR HP 2DRM41


66

3.7.2 Winchester Expert 23DLH02

Interestingly, this Winchester ammunition type was found to contain an extra

constituent; 2, 4-dinitrotoluene (DNT). It was also found to contain DEPH, DPA,

EC, DBPH and 2-nitro-DPA, similar to Winchester Laser as shown before. The

variation in DNT concentration between the two samples was found to be 53%.

DEPH was found to have 75% variation, DPA showed 13.9% variation, EC showed

19% variation, DBPH showed 15% variation and 2-nitro-DPA showed 40%

variation. This is shown in figure 3.35.

Winchester Expert 23DLH02

13018543

7817919

29428 109952472540

1406662202

6645549

11199852

66117381547

245960

2000000

4000000

6000000

8000000

10000000

12000000

14000000


Component

Pea

k A

rea

Expert 1

Expert 2

Figure 3.35: Winchester Expert 23DLH02

3.7.3 Winchester Winner IDKE52

The level of variation between the two samples is significant for this type of

ammunition. Whilst in one propellant sample, DNT was detected in the other it was

not. The same observation applies to DEPH and 2-nitro-DPA. The level of variation


67

for all constituent concentrations was over 90%. This could indicate propellant make

up differences, human or random error. This is shown in figure 3.36.

Winchester Winner IDKE52

67272 34122

12412663

411209

8228937

726200 0

750668

34599

654262

00

2000000

4000000

6000000

8000000

10000000

12000000

14000000


Component

Pea

k A

rea

Winner 1

Winner 2

Figure 3.36: Winchester Winner IDKE52

3.7.4 Winchester Subsonic LR Rim fire AED1FH31

The number of constituents detected for this type of ammunition was significantly

lower than previous ammunition types. DPA, EC and DBPH were the only

constituents detected. The level of variation for DPA had dropped significantly to

0.6%. EC and DBPH showed a variation of 18% and 11% respectively. No DNT,

DEPH or 2-nitro-DPA were detected indicating that this type of ammunition is

chemically different to other types of Winchester ammunition. This is shown in

figure 3.37.


68

Winchester Subsonic Long Rifle Rimfire AED1FH31

0

34122

00 0 0

38872

277880

526481

31802

246360

523411

0

100000

200000

300000

400000

500000

600000


Component

Pea

k A

rea

Subsonic 1

Subsonic 2

Figure 3.37: Winchester Subsonic LR Rim fire AED1FH31

3.7.5 Winchester Superspeed LR HV solid SDSB51

Again, this ammunition type was found to contain only three main constituents;

DPA, EC and DBPH. The level of variation between each of the constituents was

found to be: DPA (11%), EC (20%) and DBPH (11%). Again, no DNT, DEPH or 2-

nitro-DPA was detected in either Superspeed sample. It is interesting to note the

larger response for DBPH as opposed to that of DPA in this ammunition type,

compared to the subsonic samples previously. Figure 3.38 shows the results.


69

Winchester Superspeed Long Rifle High Velocity solid 2DSB51

0 0

722919

00 0

894639

0

808693

35690 42846

641360

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1000000


Component

Pea

k A

rea

Solid 1

Solid 2

Figure 3.38: Winchester Superspeed LR HV solid 2DSB51

3.7.6 Winchester Superspeed LR HV hollow point 2DRL62

The chemical make up of this type of ammunition is very similar to the solid

propellant type described previously. Three main constituents were again detected;

DPA, EC and DBPH. However, in this instance the Superspeed hollow point

propellant showed greater amounts detected of DPA as opposed to the Superspeed

solid propellant. The level of variation between the two samples of Superspeed

hollow point propellant samples was found to be 15% (DPA), 20% (EC) and 30%

(DBPH). Figure 3.39 shows these results.


70

Winchester Superspeed Long Rifle High Velocity Hollow Point 2DRL62

0 0 00 0

1044449

520898

0

906741

401057

46743 55838

0

200000

400000

600000

800000

1000000

1200000


Component

Pea

k A

rea

Super 1

Super 2

Figure 3.39: Winchester Superspeed LR HV hollow point 2DRL62

Table 3.7 shows the peak areas for the six different Winchester types. Significant

variation for each type was observed between the two propellant samples. This

complements the earlier results suggesting that batch determination is not possible

due to the constituent concentration variation within each batch of ammunition and

sample degradation by oxygen and auto-catalytic reactions. However, while it is the

case that batch determination is not possible, from table 3.7 it is clear that significant

difference exists between different types of ammunition. One of the types contained

five constituents (Laser type), two types contained six constituents (Expert and

Winner types) whilst the other types studied contained three constituents (Subsonic,

Superspeed solid and Superspeed Hollow point).


71

Table 3.7: Type determination of Winchester ammunition

TYPE DETERMINATION OF WINCHESTER AMMUNITION

2,4 DNT DEPH DPA EC DBPH 2-nitro-DPA

LASER 1 0 113537 12090531 399766 5839487 69363

LASER 2 0 25910 12367704 452139 6050093 77941

EXPERT 1 62202 14066 13018543 472540 7817919 109952

EXPERT 2 29428 24596 11199852 381547 6645549 66117

WINNER 1 67272 34122 12412663 411209 8228937 72620

WINNER 2 0 0 750668 34599 654262 0 SUBSONIC 1 0 0 526481 38872 277880 0

SUBSONIC 2 0 0 523411 31802 246360 0

SOLID 1 0 0 722919 35690 808693 0

SOLID 2 0 0 641360 42846 894639 0

SUPER 1 0 0 906741 46743 401057 0

SUPER 2 0 0 1044449 55838 520898 0

It is not recommended to discriminate these types of ammunitions based on the

quantity of each constituent as it varies between rounds of ammunition.

Discrimination could be performed on the basis of constituents in each type of

ammunition. For example, Expert type ammunition could be discriminated from

Laser type ammunitions based on the presence of DNT. It may be possible to

distinguish between ammunition based on the concentrations of DPA, EC and

DBPH. In a crime scene scenario, it would be recommended to analyse more than

two controls to gain a better measure of the variation found within that box of

ammunition. In that way, an average or range of DPA, EC and DBPH concentrations

could be obtained for that particular box of ammunition and the recovered propellant

sample could then be compared to the average or range.


72

�� &RQFOXVLRQV�DQG�)XWXUH�:RUN��

�� &RQFOXVLRQV�� The possibility of discriminating batches of ammunition based on their organic

composition has been deemed to be difficult. The chemical nature of some of the

compounds present in the propellant means that they are reactive compounds.

Therefore, to match propellant samples back to a known source is impossible. For

example, it has been mentioned that diphenylamine is a propellant stabilizer and is

present to react with free nitrogen oxides to prevent auto ignition of the propellant.

As a consequence, diphenylamine is a reactive compound and is not a suitable

analyte to use for batch discrimination. The compound ethyl centralite is quite

similar in chemical function and therefore is also reactive and unstable. The only

stable organic compounds present in propellant are the phthalates or plasticizers. It

could be argued that ammunition from different sources could be differentiated based

on the concentration of the phthalates present, even on the different types of

phthalates present. However, the variations within the same batch of ammunition

would need to be further explored. Conversely, it may be argued that due to the

abundance of phthalates in our everyday lives, discriminating ammunition using this

common compound may not be valid. Furthermore, the exact chemical make up of

propellant and smokeless powders remains unclear [45]. My own observations of the

manufacturing process support this claim.

Throughout the project, the effects of oxygen are apparent. Removing oxygen from

the samples did play a significant role in preserving the representative chemical

make up of the propellant. Furthermore, extracting the nitrocellulose component

from the propellant extract did benefit the project in that it removed the source of

further nitration and reactions. However, it was shown that the homogeneity of the

propellant could not be established as varying concentrations of propellant are placed


73

randomly in each cartridge case. Manufacturing companies are interested in barrel

pressure of the ammunition, not the mass of the charge.

Even though the possibility of batch determination could not be carried out, new

extraction techniques and improved methodologies have been established that could

benefit the study of unfired propellants and organic gun shot residue. Furthermore it

is suggested that brand determination of the ammunition may be a possibility.

�� )XWXUH�:RUN�

Future studies should be carried out, however, the focus of these studies should be on

brand and types of ammunitions as opposed to batches. It was shown that different

types of ammunition have different chemical compositions and therefore could be

discriminated based on this characteristic. A more comprehensive study of different

Winchester ammunition types could reveal chemical differences and therefore could

be useful to law enforcing agencies. Furthermore, studies of different brands of

ammunition could also reveal diverse chemical compositions. A database could be

created to indicate whether a propellant sample recovered from a crime scene, could

be similar in chemical composition to different brands of ammunition found in

Australia and overseas. Another study which could explore the possibility of

handling the propellant under nitrogen includes opening a cartridge case under

nitrogen and collecting the propellant sample. Half of the sample could be stored

under nitrogen for a set period of time whilst the other is subjected to open air for the

same period of time. The subsequent extraction and analysis of the two separated

propellant samples could provide a direct comparison between the storage and

manipulation methods.

Whilst batch matching may not be a possibility, unfired propellant analysis may be

able to give the police useful information into the likely sources of the recovered

propellant sample. Therefore this type of analysis could play an integral role in the

field of forensic science.


74

$33(1',;�

Ethyl Centralite standard


75

Dibutyl phthalate standard


76

Diphenylamine standard

��


77

��

Winchester Laser Long Rifle Hollow point 2DRM41

(A – Diethylphthalate; B – Diphenylamine; C –N, N diphenylformamide; D – Ethyl

Centralite; E – Dibutyl phthalate; F: 2-nitro-diphenylamine)


78

Winchester Expert 23DLH02

(A – 2,4 Dinitrotoluene; B – Diethylphthalate; C – Diphenylamine; D – N,N-

diphenylformamide; E – Ethyl centralite; F – Dibutyl phthalate; G – 2-nitro

diphenylamine)


79

�Winchester Winner IDKE52

(A – 2,4 Dinitrotoluene; B – Diethylphthalate; C – Diphenylamine; D – N,N

Diphenylformamide; E – Ethyl Centralite; F – Dibutyl phthalate; G – 2-nitro

diphenylamine)


80

�Winchester Subsonic Long rifle Rim fire AED1FH31

(A – Diphenylamine; B – Ethyl centralite; C – Dibutyl phthalate)

Winchester Superspeed Long Rifle High velocity solid 2DSB51

(A –Diphenylamine; B – Ethyl Centralite; C – Dibutyl phthalate)


81

Winchester Superspeed long rifle high velocity hollow point 2DRL62

(A – Diphenylamine; B – Ethyl centralite; C – Dibutyl phthalate)


82

5()(5(1&(6

1 Wrobel, H., Kijek, M, Millar, J (1998) Identification of Ammunition from

gunshot residues and other cartridge related materials - A preliminary model

using 0.22 caliber rimfire ammunition. Journal of Forensic Sciences 43 (2),

324-328

2 D’Uffizi, M., Falso, G, Ingo, G, Padeletti, G. (2002) Microchemical and

micromorphological features of gunshot residue observed by combined use of

AFM, SA-XPS and SEM + EDS. Surface and interface analysis 34, 52-506

3 Garofano, L., Capra, M, Ferrari, F, Bizzaro, G, Di Tullio, D, Dell’Olio, M,

Ghitti, A. (1999) Gunshot residue further studies on particles of

environmental and occupational origin. Forensic Science International 103,

1-21

4 Romolo, F., Margot, P. (2001) Identification of gunshot residue: a critical

review. Forensic Science International 119, 195-211

5 Singer, R., Davis, D, Houck, M. (1996) A survey of gunshot residue analysis

methods. Journal of Forensic Sciences 41 (2), 195-198

6 Bull, S., Roux, C, Dawson, M, Lennard, C. (2001) Organic propellant and

explosives analysis by LC/MS/MS. 13th Interpol Forensic Science

Symposium, Lyon, France

7 Krcma, V. (1996) Fluted and annular grooved barrel chambers in firearms.

Journal of Forensic Sciences 41 (3), 407-417

8 Corporation, M. (2001) How stuff is Made: The modern bullet cartridge (Vol.

2008), Windows Live

9 Meng, H., Caddy, B. (1997) Gunshot residue analysis - A review. Journal of

Forensic Sciences 42 (4), 553-570

10 Bergens, A., Danielsson, R (1995) Decomposition of diphenylamine in

nitrocellulose based propellants - II. Application of a numerical model to

concentration-time data determined by liquid chromatography and dual-

wavelength detection. Talanta 42 (2), 185-196

11 Bergens, A., Danielsson, R. (1995) Decomposition of diphenylamine in

nitrocellulose based propellants - I. Optimization of a numerical model to

concentration-time data for diphenylamine and its primary degradation

products determined by liquid chromatography with dual-amperometric

detection. Talanta 42 (2), 171-183

12 Bohn, M., Vok,F. (1992) Aging behaviour of propellants investigated by heat

generation, stabilizer consumption and molar mass degradation. Propellants,

Explosives, Pyrotechnics 17, 171-178

13 Elliot, M., Smith, F. (2000) Synthetic procedures yielding targeted nitro and

nitroso derivatives of the propellant stabilizer diphenylamine, N-Methyl-4-

nitroaniline, and N,N‘-diphenylurea. Propellants, Explosives, Pyrotechnics

25, 31-36

14 Lussier, L., Gagnon, H. (2000) On the chemical reactions of diphenylamine

and its derivatives with nitrogen dioxide at normal storage temperature

conditions. Propellants, Explosives, Pyrotechnics 25, 117-125

15 Martinez, A., Tascon, M, Vazquez, M, Sanchez Batanero, P. (2004)

Polarographic study on the evolution of the diphenylamine as stabilizer of the

solid propellants. Talanta 62, 165-173


83

16 Moriarty, R., Richardson, A, Lee, D, Patel, J, Liu, J. (1991) Reaction of

diphenylamine and n-nitroso diphenylamine with NO2 in cellulose. 5th

International Gun propellant and propulsion symposium, 481-497

17 Tong, Y., Wu, X, Yang, C, Yu, J, Zhang, X, Yang, S, Deng, X, Xu, Y, Wen,

Y. (2001) Determination of diphenylamine stabilizer and its nitrated

derivatives in smokeless gunpowder using a tandem MS method. The Analyst

126, 480-484

18 Keto, R. (1989) Comparison of smokeless powders by pyrolysis capillary gas

chromatography and pattern recognition. Journal of Forensic Sciences 34 (1),

74-82

19 Heramb, R., McCord, B. (2002) The manufacture of smokeless powders and

their forensic analysis: A brief review. Forensic Science Communications 4

(2)

20 Meng, H., Caddy, B. (1996) High-performance liquid chromatographic

analysis with fluorescence detection of ethyl centralite and 2,4-dinitrotoluene

in gunshot residue after derivatization with 9-fluorenylmethylchloroformate.


21 Aebi, B., Bernard, W. (1999) Gas chromatography with dual mass

spectrometric and nitrogen-phosphorus specific detection: a new and

powerful tool for forensic scientists. Forensic Science International 102, 91-

101

22 Burns, D., Lewis, R. (1995) Analysis and characterisation of nitroglycerin-

based explosives by gas chromatography-mass spectrometry. Analytica

Chimica Acta 307, 89-95

23 Cropek, D., Kemme, P, Day, J. (2002) Use of pyrolysis GC/MS for predicting

emission byproducts from the incineration of double-base propellant.

Enironmental Science and Technology 36 (20), 4346-4351

24 Sigman, M., Ma, C. (2001) Detection limits for GC/MS analysis of organic

explosives. Journal of Forensic Sciences 46 (1), 6-11

25 Zeichner, A., Eldar, B, Glattstein, B, Koffman, A, Tamiri, T, Muller, D.

(2003) Vacuum collection of gunpowder residues from clothing worn by

shooting suspect, and their analysis by GC/TEA, IMS and GC/MS. Journal of


26 Mach, M., Pallos, A, Jones, P. (1977) Feasibility of gunshot residue detection

via its organic constituents. Part I: Analysis of smokeless powders by

combined gas chromatography-chemical ionization mass spectrometry.

Journal of Forensic Sciences, 433-445

27 Mach, M., Pallos, A, Jones, P. (1977) Feasibility of gunshot residue detection

via its organic constituents. Part II: A gas chromatography-mass spectrometry

method. Journal of Forensic Sciences, 446-455

28 Wu, Z., Tong, Y, Yu, J, Zhang, X, Pan, C, Deng, X, Xu, Y, Wen, Y. (1999)

Detection of N,N‘-diphenyl-N,N‘-dimethylurea (methyl centralite) in gunshot

residues using MS-MS method. The Analyst 124, 1563-1567

29 Wu, Z., Tong, Y, Yu, J, Zhang, Yang, C, Pan, C, Deng, X, Wen, Y, Xu, Y.

(2001) The utilization of MS-MS method in detection of GSRs. Journal of


30 Curtis, N. (1990) Isomer distribution of nitro derivatives of diphenylamine in

gun propellants: Nitrosamine chemistry. Propellants, Explosives,

Pyrotechnics 15, 222-230


84

31 Drzyzga, O. (2003) Diphenylamine and derivatives in the environment: a

review. Chemosphere 53, 809-818

32 Curtis, N., Rogasch, P. (1987) Determination of derivatives of diphenylamine

in Australian gun propellant by High performance liquid chromatography.

Propellants, Explosives, Pyrotechnics 12, 158-163

33 Jelisavac, L., Filipovic, M. (2002) A kinetic model for the consumption of

stabilizer in single base gun propellants. Journal of Seb.Chem.Soc 67 (2),

103-109

34 Curtis, N., Berry, P. (1989) Derivatives of ethyl centralite in Australian gun

propellants. Propellants, Explosives, Pyrotechnics 14, 260-265

35 Thornton, E. (1994) Characterisation of smokeless powders by means of

diphenylamine stabilizer and its nitrated derivatives. Analytica Chimica Acta

288, 57-69

36 Mathis, J., McCord, B. (2003) Gradient reversed-phase liquid

chromatographic-electrospray ionization mass spectrometric method for the

comparison of smokeless powders. Journal of Chromatography A 988, 107-

116

37 Wissinger, C., McCord, B. (2002) A gradient reversed phased HPLC

procedure for smokeless powder comparison. Journal of Forensic Sciences

47 (1), 168-174

38 Stich, S., Bard, D, Gros, L, Wenz, W, Yarwood, J, Williams, K. (1998)

Raman Microscopic identification of gunshot residues. Journal of Raman

Spectroscopy 29, 787-790

39 Coumbaros, J., Kirkbride, K.P, Klass, G, Skinner, W. (2001) Characterisation

of 0.22 caliber rimfire gunshot residues by time-of-flight secondary ion mass

spectrometry (TOF-SIMS): a preliminary study. Forensic Science

International 119, 72-81

40 Mahoney, C., Gillen, G, Fahey, A. (2006) Characterization of gunpowder

samples using time-of-flight secondary ion mass spectrometry (TOF-SIMS).

Forensic Science International 158, 39-51

41 Kee, T., Hamill, J. (1990) The identification of individual propellant

particles. Journal of Forensic Sciences 30, 285-292

42 Meng, H. (1994) Fluoresence detection of Ethyl Centralite in Gunshot

residues. Journal of Forensic Sciences 39 (5), 1215-1226

43 MacChrehan, W.R., M; Duewer, D. (2002) A Quantitative comparison of

Smokeless powder measurements. Journal of Forensic Sciences 47 (6), 1283-

1287

44 Smith, K., McCord, B, MacCrehan, W, Mount, K, Rowe, W. (1999)

Detection of smokeless powder residue on pipe bombs by micellar

electrokinetic capillary electrophoresis. Journal of Forensic Sciences 44 (4),

789-794

45 MacChrehan, W.B., M. (2006) Development of a smokeless powder

reference material for propellant and explosives analysis. Forensic Science

International 163, 119-124

46 Northrop, D. (2001) Gunshot residue analysis by Micellar electrokinetic

capillary electrophoresis assessment for application to casework. Part II.



85

47 Northrop, D. (2001) Gunshot residue analysis by micellar electrokinetic

capillary electrophoresis assessment for application to casework. Part I.


48 Northrop, D. (1992) Sample collection, preparation and quantitation in the

micellar electrokinetic capillary electrophoresis of gunshot residues. Journal

of Liquid Chromatography 15 (6-7), 1041-1063

49 Collins, P., Lynch, G, Kirkbride, K, Skinner, W, Klass, G. (2003) Glass

containing gunshot residue particles: A new type of highly characteristic

particle? Journal of Forensic Sciences 48 (3), 1-16

50 Kurnar, R. (1999) A mass spectral guide for quick identification of phthalate

esters. In American Laboratory (Vol. 33-35)

51 McLafferty, F.W. (1980) Interpretations of mass spectra: 3rd Edition,

Cornell University

52 MacChrehan, E.D., D; Reardon, M. (2002) Associating gunpowder and

residues from commercial ammunition using compositional analysis. Journal

of Forensic Sciences 47 (2), 260-266

53 MacChrehan, W.P., E; Duewer, D; Reardon, M. (2001) Investigating the

effect of changing ammunition on the composition of Organic additives in

gunshot residue (OGSR). Journal of Forensic Sciences 46 (1), 57-62

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