M.R. Menlyadiev, G.A. Eiceman
Department of Chemistry and Biochemistry
New Mexico State University
Las Cruces, NM 88003, USA
J.A. Stone
Department of Chemistry
Queen`s University
Kingston, ON K7L 3N6, Canada
TANDEM DIFFERENTIAL
MOBILITY SPECTROMETRY
1
TA
ND
EM
IO
N M
OB
ILIT
Y
SP
EC
TR
OM
ET
ER
198
5
(C
on
tra
ct
DA
AA
15-8
5-C
-0030)
2
TANDEM DMS-IMS2
G.A Eiceman, et al., Characterization of positive and negative ions
simultaneously through determination of K & ΔK by tandem DMS-
IMS2 ISIMS 2005, Paris 3
TANDEM DMS-IMS2
4
2 4 3
0
5
CV
(vo
lts
)
Drift Time (ms)
MH+
DMS-IMS2 & ORTHOGONALITY IN K AND ΔK
Alpha function modification
AH+ + B -------> AHB+ -------> AH+ + B
Stable ion/neutral cluster formation
AH+ + B -------> AHB+
Charge stripping
AH+ + B -------> A + BH+
Ion fragmentation (thermal, field, photo)
AH+ -------> M + BH+
RF field
6
POSSIBLE CHEMICAL PATHS TO ION
MODIFICATIONS
Purified air 0.1% CH2Cl2 in air
G.A
. E
icem
an
et
al.
, A
nal.
Ch
em
. 2004,
76,
4937-4
944
7
EXAMPLE OF CHEMICAL MODIFICATION
WITH CHANGE IN ALPHA PARAMETER
Most of today`s DMS have R<80 (typically ~20)
Ions with MW> ca. 150 are poorly resolved under normal conditions
One DMS analyzer is easily used to isolate ions for later ion chemistry studies
A tandem DMS/DMS is mechanically convenient and functionally simple
8
MOTIVATIONS FOR DMS/DMS
9
FIRST DMS/DMS/MS STUDY (PITTCON 2010)
Eiceman G.A. “Ion preparation before differential mobility spectrometry
including DMS/DMS analyzers”, Pittcon 2010
10
EXPERIMENTAL APPARATUS FOR
DMS/DMS/MS STUDIES
-20 -15 -10 -5 0 5
-20
-15
-10
-5
0
5
Inte
nsity
(a.u
.)
HeptanoneC:\Documents and Settings\hschmidt\My Documents\Hartwig\DMS DMS\20100226\
&G - Graph3D_heptanoneonly - 2/26/2010 21:23
Compensation Voltage fast (V)
Com
pensation V
oltage s
low
(V
)
10000
1.825E5
3.55E5
5.275E5
7E5
11
DMS/DMS ANALYSIS OF TRACE VAPOR
LEVELS OF 2-HEPTANONE IN PURIFIED AIR
CV
DM
S1
CVDMS2
-20 -15 -10 -5 0 5 -20
-15
-10
-5
0
5
RIP
MH+
M2H+
Purified air w/butanol
12
ION SELECTIVE PLOT FOR MH+ (m/z 115) OF
2-HEPTANONE
CV
DM
S1
CVDMS2
-20 -15 -10 -5 0 5
-20
-15
-10
-5
0
5
m/z 115C:\Documents and Settings\hschmidt\My Documents\Hartwig\DMS DMS\20100226\
20100226_1922_heptanone_extr_masses_DMSDMS - Graph115 - 2/28/2010 00:07
Inte
nsity (
a.u
.)
Compensation Voltage fast (V)
Com
pensation V
oltage s
low
(V
) 100.0
1.258E4
2.505E4
3.753E4
5E4
-15 -10 -5 0 5
-15
-10
-5
0
5
-20 -20
-20 -15 -10 -5 0 5
-20
-15
-10
-5
0
5
m/z 115
Inte
nsity (
V)
C:\Documents and Settings\hschmidt\My Documents\Hartwig\DMS DMS\20100226\
20100226_2024_extr_masses_butanol_heptanone - Graph115 - 2/27/2010 23:50
Compensation Voltage fast (V)
Com
pensation V
oltage s
low
(V
)
1000
7.075E4
1.405E5
2.103E5
2.8E5
-15 -10 -5 0 5
-15
-10
-5
0
5
-20 -20
(-3.5;-6.5) (-3.5;-1.5)
0.5 mm
DMS 1 Electronics &
PC Control
DMS 2 Electronics & PC
Control
Gas Flow Control with
Sample
Gas Flow Control with
Dopant
Faraday Plate &
Amplifier
5 mm
CVDMS1
SVDMS1
Det (-)
Det (+)
SVDMS2
CVDMS2
2 mm
13
BLOCK DIAGRAM of DMS/DMS WITH
FARDAY PLATE DETECTORS
0.5 mm
-20 -15 -10 -5 0 5 10-20
-10
0
10
Negative
CV 2, Volts
CV
1, V
olts
0.06000
0.09500
0.1300
0.1650
0.2000
0.2350
0.2700
0.3050
0.3400
-20 -15 -10 -5 0 5 10
-20
-15
-10
-5
0
5
10
Positive
CV2, Volts
CV
1, V
olts
0.05000
0.09375
0.1375
0.1813
0.2250
0.2688
0.3125
0.3563
0.4000
Positive Polarity Negative Polarity
-20 -15 -10 -5 0 5 10-20
-10
0
10
CV 2, Volts
CV
1, V
olts
0.06500
0.07250
0.08000
0.08750
0.09500
0.1025
0.1100
0.1175
0.1250
-20 -15 -10 -5 0 5 10
-20
-15
-10
-5
0
5
10
Positive
CV 2, Volts
CV
1, V
olts
0.08000
0.09375
0.1075
0.1213
0.1350
0.1488
0.1625
0.1763
0.1900
-20 -10 0 10-20
-15
-10
-5
0
5
10
Positive
CV 2, Volts
CV
1, V
olts
0.08000
0.09750
0.1150
0.1325
0.1500
0.1675
0.1850
0.2025
0.2200
H+(H2O)n
H+(H2O)n
H+(H2O)n O2
-(H2O)n
CVDMS2, V
CV
DM
S1, V
14
RF STEERING OF ION PEAKS FOR RIP
(IDENTICAL OPERATION TEST)
O2-(H2O)n
O2-(H2O)n
SVDMS1=SVDMS2=0VV
SVDMS1=500V VDMS2=900VV
SVDMS1=900V VDMS2=500VV
-20 -10 0 10-20
-10
0
10Negative
CV 2, Volts
CV
1, V
olts
0.06000
0.07125
0.08250
0.09375
0.1050
0.1163
0.1275
0.1388
0.1500
-20 -10 0 10
-20
-10
0
10
O2-(H2O)n
(0;0) (0;0)
(-4;-18) (-3;-15)
(-18;-4) (-15;-3)
CV
DM
S1, V
CVDMS2, V 15
RF STEERING OF ION PEAKS FOR SAMPLE
(IDENTICAL OPERATION TESTS)
-30 -20 -10 0 10
-30
-20
-10
0
10
CV 2, Volts
CV
1,
Vo
lts
0.06000
0.08000
0.1000
0.1200
0.1400
0.1600
0.1800
0.2000
0.2200
O2-(H2O)n
MO2-(H2O)n
SVDMS1=SVDMS2=700VV
(-3;-3)
(-10;-10)
connection
DMS1 DMS2 Tube
a
b
Sample gas flow 1.5 L/min
Dopant gas flow 0.2 L/min
c
Flo
w v
elo
city
, m/
s
16
COMSOL FLOW MODELING IN DMS/DMS
(FLOW DINAMICS TEST)
Flow velocity map
Flow velocity map
Pressure map
17
ORTHOGONALITY W/DOPANT: MSAL
M M
IPA
1) MO2-(H2O)n + mC3H7OH M + nH2O + O2
- (C3H7OH)m
2) O2-(H2O)n + mC3H7OH nH2O + MO2
- (C3H7OH)m
`
SPARTAN
ab initio modeling
∆H = 44kJ/mol at m=1
∆H = -23kJ/mol at m=2
-30 -20 -10 0 10
-30
-20
-10
0
10
CV 2, Volts
CV
1,
Vo
lts
0.06000
0.08000
0.1000
0.1200
0.1400
0.1600
0.1800
0.2000
0.2200
O2-(H2O)n
MO2-(H2O)n
CV
DM
S1,
V
(-3;-3)
(-10;-10)
CV
DM
S1,
V
-30 -20 -10 0 10
-30
-20
-10
0
10
CV2, Volts
CV
1,
Volts
0.007000
0.008125
0.009250
0.01038
0.01150
0.01263
0.01375
0.01488
0.01600
O2-(H2O)n
MO2-(H2O)n
O2-(C3H7OH)m
O2-(C3H7OH)m
(-3;-16)
(-10;-16)
(-3;-3)
(-10;-10)
CVDMS2, V
18
Low concentration, ~ tens of ppb
CV, V
RIP
MH + M2H+
ID (characteristic CV for
each OPC)
CV, V
Higher concentration or interferences
M2H+
Difficult to identify
HOW TO INCREASE PEAK
CAPACITY FOR OPCs IN DMS?
ORTHOGONALITY THROUGH DOPANT:
OPCs CASE
19
ORTHOGONALITY THROUGH DOPANT:
OPCs CASE
DMMP
CVDMS2, V
20
Inte
nsi
ty,
V
DMS2 SPECTRUM OF (DMMP)2H+ ION
SELECTED BY CV IN DMS1
10 -10 -20 -30 0
0
0.1
0.2
CVDMS2, V
M
0
10 -10 -20 -30 0
Inte
nsity,
V
CVDMS2, V -30 -20 -10 0 10
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
Inte
nsity
, V
CV, Volts
isopropanol
0.1
21
1% IPA CONTROL SPECTRUM
IPA
IPA
0
10 -10 -20 -30 0
Inte
nsity,
V
CVDMS2, V
-30 -20 -10 0 10
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
Inte
nsity
, V
CV, Volts
DMMP
isopropanol
0.1
22
DMS2 SPECTRUM OF (DMMP)2H+ ION
SELECTED BY CV IN DMS1 with 1% IPA AS DOPANT
M
IPA
23
Inte
nsity,
V
10 -10 -20 -30 0
0
0.1
TBP
CVDMS2, V
DMS2 SPECTRUM OF (TBP)2H+ ION
SELECTED BY CV IN DMS1
M
24
DMS2 SPECTRUM OF (TBP)2H+ ION
SELECTED BY CV IN DMS1 with 1% IPA AS DOPANT In
ten
sity
, V
CVDMS2, V -30 -20 -10 0 10
0.10
0.12
0.14
0.16
0.18
0.20
Inte
nsi
ty, V
CV, Volts
TBP
0
0.1
10 -10 -20 -30 0
b isopropanol
M
IPA
-30 -20 -10 0 10
0.10
0.12
0.14
0.16
0.18
0.20
Inten
sity,
V
CV, Volts
TBP
0
0
0.1
10 -10 -20 -30 0
Inte
nsity,
V
CVDMS2, V
-30 -20 -10 0 10
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
Inten
sity,
V
CV, Volts
DMMP
isopropanol
0.1
a
b isopropanol
25
COMPARISON OF DOPANT EFFECTS FOR
(DMMP)2H+ AND (TBP)2H
+ IONS
1) M2H+ + nC3H7OH M2H+ (C3H7OH)n
2) M2H (C3H7OH)n M2H+ (C3H7OH)n-x + M+ xC3H7OH
26
PRELIMINARY INTERPRETATION OF REACTION
OF (DMMP)2H+ AND (TBP)2H
+ IONS WITH
ISOPROPANOL
M. R. Menlyadiev, J.A. Stone, G.A. Eiceman, “Tandem differential mobility
spectrometry with chemical modification of ions,” Int. J. Ion Mobil. Spec. 2012
(to be published, now available online)
27
ION FRAGMENTATION: A WAY TO INCREASE
PEAK CAPACITY IN DMS
MO2 (M-H)- + HO2-
RF field
CVDMS2 , V
CV
DM
S1 ,
V
-20 -10 0
-30
-20
-10
0
10
CV 2, Volts
CV
1, V
olts
0.06000
0.08000
0.1000
0.1200
0.1400
0.1600
0.1800
0.2000
0.2200
O2-(H2O)n
M*O2-(H2O)n
(-3:-3)
(-10:-10)
SVDMS1= 700V
SVDMS2= 700V
SVDMS1= 700V
SVDMS2= 1400V
-20 -10 0
-30
-20
-10
0
10
CV 2, Volts
CV
1, V
olts
0.07500
0.08188
0.08875
0.09563
0.1025
0.1094
0.1163
0.1231
0.1300
(M-H)-
(-3:-8)
28
DMS/DMS OPERATION MODES
1.DMS1 CV ion selection, DMS2 CV scan (similar to
product ion scan in MS/MS)
2. DMS1 CV scan, DMS2 CV ion selection (similar to
parent ion scan in MS/MS)
3. DMS1 CV scan and DMS2 CV scan with fixed
(CV2-CV1) offset value (similar to neutral loss scan
in MS/MS)
4. DMS1 ion selection, DMS2 ion selection (similar
to SRM in MS/MS)
DMS/DMS in mobility spectrometry, as MS/MS in mass
spectrometry, is based on idea that chemical properties of
ions, can be employed to increase specificity of ion
characterization and identification in mobility analyses
DMS/DMS is a versatile platform for studying chemical
orthogonality in DMS by exploring various gas phase
chemical phenomena
The tandem system is flexible with multiple modes of
operation, tailorable to specific applications
29
SUMMARY
Better control of DMS1 and DMS 2 electronics
and synchronicity of operation
Mass identification with new reactions
Elimination of excessive neutrals present in
DMS1 (for ESI work)
30
FUTURE PLANS
Dr. H. Schmidt (Morpho
Detection)
Dr. E. Nazarov (Draper
laboratory)
John Tobin (NMSU)
Aldo Maldonado (NMSU)
31
ACKNOWLEDGEMENTS