Jordan Journal of Chemistry Vol. 7 No.3, 2012, pp. 311-328

311

JJC

Identification of Polycyclic Aromatic Hydrocarbons in Air Samples from Zarqa City, Jordan, Using High Resolution Laser Excited Luminescence Spectroscopy Combined with Shpolskii Matrix

Technique

Yaser A. Yousef∗, Ahmed A. Alomary, Abdulrahman Shwayat, Idrees F. Almomani

Chemistry Department, Faculty of Science, Yarmouk Univesity, Irbid, Jordan Received on June 6, 2012 Accepted on July 12, 2012

Abstract Laser excited luminescence combined with Shpolskii matrix techniques were used for the

detection and identification of PAH pollutants in the atmosphere of the northern part of Zarqa city

in Jordan. The weather conditions in that area are dry and dusty most of the year. The presence

of the oil refinery plant and the thermal power station in addition to most of the local industries

are considered as the major sources of pollution to the atmosphere of that area. The extent of

pollution was detected by measuring the concentration levels of Polycyclic Aromatic

Hydrocarbons (PAHs). Air samples from the airborne of Zarqa were collected at different time

intervals using high volume air sampler. A clean-up procedure, soxhlet extraction, was used

before subjecting samples to analysis. Gas Chromatography (GC) was used for quantitative

analysis of sample components. Cooling the samples down to 77K was sufficient to produce an

environment similar to Shpolskii matrix which is necessary for resolving the complex

fluorescence spectra of PAH compounds. PAHs of low molecular weights such as fluorine,

phenanthrene, chrysene, and the most dangerous carcinogen namely benz(a)pyrene, were

dominant in all samples. The total average of PAHs concentration varied from (7.3 ng/m3) for

benz(a)pyrene to (48.3 ng/m3) for phenanthrene.

Keywords: Benz(a)pyrene; GC; Laser Excited Luminescence (LEL); PAHs; Zarqa.

Introduction Air pollution has long been a severe problem facing human beings. From

several air pollutants, it is of particular interest to concentrate on the most dangerous

group, namely polycyclic aromatic hydrocarbons (PAHs)[1,2,3]. They are sometimes

referred to as polynuclear aromatic hydrocarbons or as polycyclic aromatic

compounds. Aromatics (including PAHs) are considered to be the most acutely toxic

component of petroleum products, and are also associated with chronic and

carcinogenic effects [4]. Most of PAHs with low vapor pressure in air are adsorbed on to

the surface of the dust particles. Therefore, they are believed to be major contributors

to the higher death rate from lung cancer in urban areas as compared to rural

areas[5,6].

∗ Corresponding author: e-mail: yhaj@yu.edu.jo

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Zarqa, the second largest city in Jordan and home of 52% of the industries in

the country, suffers the worst water shortage and air pollution. Zarqa's climate is

desert-like, to a much greater degree than nearby Amman. The major air pollution

sources in the city are the national refinery complex and Hussein thermal power

station. The determination of the levels of PAHs in the air of that area is of great

importance for the whole country.

One of the most sensitive techniques used for detecting PAHs is the Laser

Excited Fluorescence (LEF) which can reach limits of detection several orders of

magnitude higher than Gas Chromatography (GC) and High Performance Liquid

Chromatography (HPLC) [7,8]. Recent advances in LEF have shown the possibility of

single molecule detection [9,10,11]. Combining LEF with Shpolskii matrix individual PAH

compounds can be identified without the need of using classical chromatographic

separation techniques [12,13]. Cooling the samples in a proper solvent highly enhances

the fluorescence intensity and significantly reduces the width of the fluorescence

bands. Cryogenic temperatures close to 10 K is one of the necessary conditions to

produce fluorescence lines characteristic to Shpolskii matrix. Solvent chain length,

concentration and excitation line width are the other necessary conditions. It was

believed that only at this range of temperature, the width of the fluorescence lines

becomes sharp enough to be used for the identification of PAH compounds. In this

work, similar resolution could be achieved by cooling the samples to 77K using liquid

nitrogen. The success in sample analysis at this temperature is expected to make the

technique more popular due to the low cost in using liquid nitrogen as compared to the

cost and difficulty in using liquid helium. It is hoped that this result will encourage

further use of the technique for environmental analysis of PAH pollutants.

Experimental Samples collection

The sampling site, selected to characterize the PAH concentrations in the

ambient air, was located in Alhashemite industrial centre 2km from the refinery

complex. The sampling of the suspended particulate matter (SPM) was carried out

using a high volume sampler (TE-5170D-BL-INT, Packwill Environmental, Canada).

The sampler was kept at the rooftop of the municipal building about 13m above the

ground. The airborne particles were collected for 6 hour time periods on glass-fibbers

filter papers (size: 8” ×10”). A standard clean up, extraction, and volume reduction

procedure were followed, as described by Wenclawiak et al.[13]. A total of thirty samples

were collected from the sampling site during the period July to December 2004.

Chemicals

Solid standards, (anthracene and pyrene), were purchased from Aldrich,

Germany, and used as received. Standard solution containing 13 PAHs (EPA 525 PAH

mix A) in methylene chloride where purchased from Subelco, USA. Details of the

standard composition are given in table 5. Spectroscopic grade n-heptane and hexane

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were purchased from Synchemica USA, and used as received. HPLC grade

dichloromethane was purchased from Aldrich. No detectable emission signals were

observed from all above solvents when excited in the range (250-500 nm). Silica and

alumina, (60 mm particle size), were purchased from Fluka. Liquid nitrogen was

obtained from the physics department.

Laser Excited Fluorescence (LEF) Set-up:

A block diagram for the LEF set-up is shown in figure 1. It is a modified version

of a home assembled system described in a previous work [14]. Nitrogen laser, PRA

(model LN-1000) (337.1 nm and 1mJ pulse energy) was used as the excitation light

source. The sample cell holder was a home designed and fabricated unit. It consists of

a pressure sealed stainless steel semi- spherical block with a quartz window. The cell

is designed for front surface excitation and emission. The topside of the cell can be

fitted to the tip of a homemade open cycle liquid nitrogen cryostat described in a

previous work [15]. Cell temperature was monitored by measuring the bias voltage

across a silicon diode fixed to the base of the cell. Chromex spectrograph (model

5001) with variable resolution is used to analyze the sample emission. It contains a set

of 3 gratings (75,150,300 grooves/mm) mounted on a turret. CCD, Princeton

Instruments (model ICCD-512x376) was used for detection. A programmable high

voltage pulsar (Princeton, model PG-200) is used to control the exposure time of the

CCD. Data acquisition, timing, and detector temperature were controlled by Model ST-

138 detector controller. Delay generator, Stanford Research Systems (model DG-535),

was used to synchronize the trigger of the high voltage pulsar with the laser and the

electromechanical shutters. Winspec software operating under Windows workgroups

V.3.11 was used to control the operation of the whole system and for data acquisition.

Gas Chromatography

GC Model-1000 from DANI Instruments was used for the separation and

quantitative analysis of the PAH compounds. The operating parameters for the unit are

listed in table 1.

Table 1: GC operating conditions

INSTRUMENT DANI GC 1000 INJECTOR Split-less mode. 250oC Detector Flame Ionization Detector (FID), 350 oC Column Capillary, 10m length x 0.53 mm id x- 2.65 µm film thickness,

Dimethyl-polysiloxane. Carrier Carrier: N2, flow 4 ml/min Oven 70 to 220 °C, rate 10 °C/min, hold time 20 min. Sample volume 5 µl

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LN-1000N2 Lasr 1 2

3

45

6 78

Spectrograph

Cryostat

ICCD (OMA IV)

ST- 138Detector controller

Comm 2Serial port

9 10

11

12 13

14

15

8 8 8

Temperature Indicator

PG - 200Fast Pulser

DG- 535Delay Generator

Oil vacuum pump

Oilless pumpLiquid nitrogen dewer

Figure 1: Low temperature fluorescence setup, (1,2 -quartz window, 3 – sample cell, 4,5,6,7 mirrors, 8-grating, 9,10 laser input output, 11 electromechanical shutter, 12,13,14 controller I/O, 15 pulsar I/O). Results and Discussion

The room temperature fluorescence spectrum for a solution of pyrene in n-

heptane is shown in figure 2.a. The spectrum is known to have a broad fluorescence

band which cannot be used for the identification of the compound in a mixture of PAHs

sample [12]. Figure 2-b shows the low temperature fluorescence spectrum of the same

sample of pyrene in n-heptane at 77 K. It is clear that it consists of highly resolved

narrow spectral lines that can be easily used as fingerprint for the molecule in high

resolution mode of analysis. The spectrum obtained here has a comparable or better

resolution than the spectrum reported by Abu-Zeid et al., although the latter was

recorded at 15K temperature [12]. This can be attributed to experimental conditions

such as the alignment optics, laser energy, and the sensitivity of the Charge Coupled

Device (CCD). The room and low temperature spectra for a number of standard

compounds such as pyrene, anthracene ..etc were recorded and stored as standard

spectra for comparison purposes. The collected spectra were in good agreement with

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those reported in the spectral atlas of organic compounds [16]. Further more, the

spectrum for a standard mixture sample containing 13 PAHs, (Subelco, EPA 525

PAHs mix A), was recorded at both room and low temperatures. The complete low

temperature spectrum was divided into four spectral frames, each of 20 nm width.

Figure 3 contains four spectral frames each shows the presence of a number of

compounds. Figure 3-a shows 9 sharp peaks related to the presence of anthracene,

benzo(a)anthracence, pyrene, and dibenzo(a,h)anthracence in the sample matrix. The

other three spectral frames are shown in their corresponding frames while the numbers

indicated above the peaks are related to the expected compounds. The spectral

frames in figure 3 could be successfully used to identify the compounds that were

detected with high sensitivity from the real samples.

Figure 2.a: Emission spectrum of pyrene solution at room temperature using low

resolution grating (150 groves/mm).

0.E+00

2.E+04

4.E+04

6.E+04

8.E+04

1.E+05

1.E+05

1.E+05

350 370 390 410 430 450 470 490

rela

tive

inte

nsity

wavelength (nm)

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Figure 2.b: Low resolution emission spectrum for the same sample in figure (2-a)

obtained at the same conditions except for the sample temperature 77K.

For demonstration purposes, the spectrum of one of the first period samples is

shown in figure 4. The results indicate the capability of the technique for the

identification of PAHs in the atmosphere. In addition, the technique has a low detection

limit; it was possible to detect all compounds in a standard mixture containing 50ng/ml

for each. Furthermore, the results indicate the presence of some PAHs in the study

area in concentrations close or higher to the concentration of the standard sample.

However, due to several experimental parameters such as variations in laser pulse to

pulse intensity, optical alignment, and internal or self absorption, the technique is

generally used for identification and semi-quantification analysis [17].

0.E+00

2.E+04

4.E+04

6.E+04

8.E+04

350 400 450 500

rela

tive

inte

nsity

wavelength (nm)

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Figure 3.a: High resolution emission spectrum for a mixture of PAH's (0.5 ppm each)

obtained at 77K, numbers indicate the characteristic peaks for the following

compounds; 1 and 2 for anthracene; 4 and 5 for benzo(a)anthracene; 3, 6, 7 and 8 for

pyrene and 9 for dibenz(a,h)anthracene.

2.E+05

2.E+05

2.E+05

3.E+05

375 380 385 390 395

rela

tive

inte

nsity

wavelength (nm)

12

3

5

6

7

8

4

9

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Figure 3.b: Emission spectrum for a mixture of PAHs (0.5 ppm each) obtained at 77K,

numbers indicate the characteristics peaks for the following compounds; 1, 7 for

benzo(a) pyrene. 2, 3,4,10 for benzo(g,h,i) perylene, 6,8, 9 for benzo(b)fluoranthene.

1

23

4 5

6

7

89

10

11

319

Figure 3.c: Third frame of emission spectrum for a mixture of PAHs (0.5 ppm each) obtained at 77K. Number (1) indicate the characteristic peak for phenanthrene molecule.

Figure 3.d: Last frame of emission spectrum for a mixture of PAHs (0.5 ppm each) obtained at 77K. All peaks are related to chrysene molecule.

6.E+04

7.E+04

8.E+04

9.E+04

1.E+05

1.E+05

458 460 462 464 466 468 470

Rel

ativ

e In

tens

ity

Wavelength (nm)

1

3.E+04

6.E+04

9.E+04

1.E+05

2.E+05

2.E+05

2.E+05

495 500 505 510 515 520

Rel

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Wavelength (nm)

320

Quantitative analysis is usually carried out using GC technique combined with

the method of internal standard. For this purpose, the collected samples were

analyzed for PAH components by GC. A 10 meter capillary column was used to

resolve the complex sample matrix. Figure 5 shows a GC chromatogram obtained for

the standard sample mixture containing 13 PAHs (EPA 525 PAH mix A). The retention

times and the peak areas for the eluted compounds are shown in table 2 and given in

figure 5.

Table 2: Retention times and peak areas for compounds recorded in figure 5.

No. Name Retention Time (min)

Peak Area

1 Acenaphthylene 7.78 380

2 Fluorine 8.80 277

3 Phenanthrene 9.95 911

4 Anthracene 10.4 1245

5 Pyrene 13.4 583.7

6 Benzo (a) anthracene 14.6 1753

7 Chrysene 15.7 1687

8 Benzo (b) fluoranthene 16.4 2128

9 Benzo (k) fluoranthene 19.1 871

10 Benzo (a) pyrene 21.9 3106

11 Indeno (1, 2, 3-cd) pyrene 22.3 1840

12 Dibenzo (a, h) anthracene 23.8 581

13 Benzo (ghi) perylene 24.2 620

321

Figure 4.a: First Frame of emission spectrum for an air polluted sample sample at 77K

using high resolution grating, numbers indicate the characteristics peaks for the

following compounds; 1, 2, 3, 4 for pyrene, 5 for dibenz(ah)anthracene.

1.E+05

1.E+05

1.E+05

2.E+05

2.E+05

2.E+05

2.E+05

2.E+05

3.E+05

380 385 390 395 400

Rel

ativ

e in

tens

ity

Wavelength (nm)

1

2

3

4

5

322

Figure 4.b: Second frame of emission spectrum for same sample in (4-a) at 77K using

high resolution grating at 77K, numbers indicate the characteristics peaks for the

following compounds; 1, 3 and 5 for benzo(a)pyrene; 4, 6, 7 and 8 for

benzo(b)fluoranthene; 2 and 9 for Benzo (g, h, i) Perylene.

1.E+05

1.E+05

1.E+05

2.E+05

2.E+05

2.E+05

2.E+05

2.E+05

2.E+05

2.E+05

2.E+05

400 405 410 415 420

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tive

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nsity

Wavelength (nm)

1

2

3

4

56

7

8

9

323

Figure 4.c: Third frame of emission spectrum at 77K. Peaks are assigned for

phenanthrene.

430.00 440.00 450.00 460.00 470.00Wavlength (nm)

4.0E+4

8.0E+4

1.2E+5

1.6E+5

2.0E+5

Rel

ativ

e In

tens

ity

1

2

3

Wavelength (nm)

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Figure 4.d: Last frame of emission spectrum at 77K.

Figure 5: GC chromatogram for 13 PAHs Standard, 1ppm each. Names retention times correspond to each peak number are summarized in table 2.

1.E+05

2.E+05

2.E+05

3.E+05

3.E+05

4.E+05

480 490 500 510 520

rela

tive

inte

nsity

Wavelength (nm)

10

40

70

100

130

5 10 15 20 25

mv

Retention time (min)

12

34

5

6 78

9

10

11

12 13

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When real samples were injected, the chromatogram was complex compared to

that of the standard. However, it was easy to pickup our compounds and identify them

by comparing their retention times with standard. The retention times and the peak

areas for the eluted compounds are shown in (Figure 6&7) and given in table 3.

Similarly, all samples collected during the different time intervals were analyzed

by GC following the same procedure and the results are summarized in tables 3 and 4.

Table 3: Retention times and peak areas for compounds recorded in figures 6 and 7.

Sample number 1-a 1-a 2-a 2-a

No. Name RetentionTime

PeakArea

Retention Time

Peak Area

2 fluorine 8.8 1230 8.8 1288

3 phenanthrene 9.9 2200 9.9 1950

6 benzo (a) anthracene 14.5 4675 14.5 5306

7 chrysene 15.8 1980 15.75 3250

10 benzo (a) pyrene 21.9 2800 21.9 2139

12 dibenzo (a, h) anthracene 23.8 1224 23.8 991

Table 4: Concentrations of PAHs (ng/m3) in collected aerosol samples.

PAH name B.a.a B.a.P B.k.f chry d.b.ah.a Flu phen

Total

Avg. 20.5 7.4 10.3 43.6 8.8 71.2 48.3

SD 27.8 11.5 18.5 43.9 8.9 39.2 25.9

A*

Avg 30.3 5.8 14.8 55.6 8.2 83.9 68.2

SD 35.1 5.9 24.5 61.7 8.0 39.1 25.2

B*

Avg 28.0 11.5 13.5 37.5 14.0 82.70 47.6

SD 27.4 17.9 19.9 31.3 10.9 35.9 20.2

C*

Avg 3.3 4.8 2.7 37.7 4.3 47.1 29.1

SD 3.2 6.1 3.0 34.3 4.1 34.0 16.4

t- test

t-test A-B 0.87 0.74 0.89 0.29 0.20 0.95 0.06

t-test A-C 0.04 0.41 0.15 0.20 0.19 0.04 0.00

t-test B-C 0.02 0.09 0.12 0.72 0.02 0.04 0.04

*: Time interval

A: time interval (6.00 am-10 am).

B: time interval (12.00 am-4.00 pm).

C: time interval (7.00 am-10.00 am).

B.a.a: benzo (a) anthracene; B.a.P: benzo (a) pyrene; B.k.f: benzo (k) fluoranthene; chry: chrysene; d.b.ah.a: dibenzo (a, h) anthracene; Flu: fluorine; phen: phenanthrene.

As it can be seen from the table, the predominant PAHs detected in our samples

were the low molecular weight PAHs. These are; phenanthrene, fluorine and chrysene.

These results are in good agreement with the results obtained using LEF. As can be

326

seen in Table 3, the highest total PAHs concentrations were during the first and

second time periods (6.00 am to 4.00 pm), which are the morning and afternoon

periods. T-test was used to check if there is a significant difference between the

concentrations in samples collected from different time intervals. Results indicated the

presence of a significant difference between the C period and both A and B periods.

Concentrations of PAHs in samples collected during the C period were generally

higher than those collected in either A or B. These higher concentrations during this

time period could be attributed to the increased human activities during the daytime

and the increased wind speed during night, which leads to dilution of concentrations in

the atmosphere.

Fluorine was found to have the highest concentration among the detected PAH

(84 ng/m3), while benzo(a)pyrene has the lowest average concentration (7.2ng/m3).

Comparison of the atmospheric data with the literature is one of the essential steps in

the atmospheric studies. Area under study is broadly classified as urban. The urban

areas are ones that are under the direct influence of the local anthropogenic

emissions. Therefore, in order to roughly know the extent of pollution in the area under

study, the result should be compared with literature data in which the pollution level is

known. Comparing the data with data obtained from resembling areas may help in

finding out the unusual results, which could be due to particular analytical problem.

Observed concentrations of PAHs are compared with those found by others in urban

areas. Therefore, literature values were also selected to be from urban areas.

Measured concentrations of PAHs in urban areas are presented together with our

results in table 5.

Table 5: Comparison of observed concentrations of PAHs (ng/m3) with reported literature data.

PAH This study

LahorePakistan

Taiwan

TaipeiChina

RomeItaly

Calcutta India

Fluo 71.2 1.0 138.5 15 - -

Phen 48.3 0.97 94.2 - - 11.2

B.a.a 20.5 5.4 14.2 9 1.27 30.2

B.a.p 7.4 9.3 9.0 1.7 1.74 43.2

B.k.f 10.3 4.61 14.5 1.1 1.19 22.4

Chry 43.6 8.6 50.7 3.3 2.8 32.2

D.b.ah.a 8.8 4.0 4.3 3.2 0.35 12.1

Fe

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Figure 6: GCeach peak ar

Figure 7: GCeach peak ar

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Acknowledgment The authors would like to thank Prof. Dr. Mohammad Al-Qudah and Dr. Natheer

Rwashdeh for their valuable discussion. This work was supported by the Deanship of

Scientific Research and Graduate Studies at Yarmouk University, project No. 017 and

IRDC Canada.

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of the Subcommittee on Air and Water Pollution, Committee on Public Works, United States Senate", U.S. Government Printing Office: U.S.A., 1968.

[3] Rand, G. M; Petrocelli, S. R., "Fundamentals of Aquatic Toxicology", Hemisphere Publishing Company: New Yourk, 1985, 666.

[4] Irwin, R. J.; VanMouwerik, M.; Stevens, L.; Seese, M. D., Basham W., "Environmental Contaminants Encyclopedia", National Park Service,Water Resources Division: Colorado, USA, 1997.

[5] Pott, F.; Heinrich, U., "International Agency for Research on Cancer (IARC)", No. 104, 1990, pp. 288–297.

[6] Cook, R. H.; et al., "Polycyclic Aromatic Hydrocarbons in Aquatic Environment: Formation, Sources, Fate and Effects on aquatic Biota", NRCC: Ontario, Canada, 1983.

[7] Wehry, E. L.; Rossiter, B.W.; Baetzold, R. C., "Physical Methods of Chemistry", vol. 8, Wiley: New York, 1993.

[8] Remediation and Redevelopment Division, Michigan Department of Environmental Quality, Operational Memorandum (2), October, 2004.

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Chemistry and Biology", Kluwer Academic Publisher, Netherlands, 1989, 2, 365. [13] Yousef, Y. A.; Abu-Zeid, M.E.; Kurdia, H., Abhath Al- Yarmouk, 1997, 6, 81. [14] Yousef, Y. A.; Fataftah Z.A.; Akasheh, T. S.; Rawashdeh, A. M., Optica Applicata, 2001

31, 563. [15] Yousef, Y. A., Optica applicata, 2005, 35, 67. [16] Karcher, W., et al.; "Spectral Atlas of Poly cyclic Aromatic Hydrocarbons", Holland, 1983. [17] Berlman, I. B.; "Handbook of fluorescence spectra of aromatic molecules", Academic

Press, 1971.