G.A. Eiceman
Department of Chemistry & Biochemistry
New Mexico State University
Las Cruces, NM 88003
TANDEM CONFIGURATIONS OF ION MOBILITY
SPECTROMETERS AT AMBIENT PRESSURE
CONCEPTS AND PRACTICES
Department of Chemistry
Loughborough University
Loughborough, Leics LE11 3TU
PRINCIPLE I. TANDEM ANALYZERS HAVE
ADVANTAGES AND ALSO SOME DISADVANTAGES.
NET RESULT IN QUANT. MEASUREMENTS = POSITIVE
APPLICATION. IONS DERIVED FROM ESI SOURCES AND
CERTAIN SAMPLES CAN BE COMPLEX MIXTURES. ION
FILTERING BY MOBILITY AT ~AMBIENT PRESSURE
BETWEEN SOURCE AND MS IMPROVES S/N.
clenbuterol in urine 5 pg/µl
MS ESI
MS ESI IMS
“if we spent a tiny fraction of the effort and
resources on ionic processes outside the vacuum
system compared to those occurring in vacuum,
progress in mass spectrometry would be
accelerated.”
Graham Cooks 2013
PRINCIPLE II. ION HANDLING AT OR NEAR
AMBIENT PRESSURE HAS ADVANTAGES OF:
a. LOW COST AND HIGH CONVENIENCE
b. OPPORTUNITY IN ION PROCESSES AVAILABLE ONLY WITH
HIGH COLLISION FREQ.
POSSIBLE CONSEQUENCE OR GOAL OF R&D PROGRAM
MASS SPECTROMETER IMS LC
MASS SPECTROMETER IMS LC
2013
2016
Eiceman, et al. “Characterization of positive and negative ions simultaneously through determination of K & ΔK by tandem DMS-IMS2 ”, ISIMS 2005, Chateau de Maffliers, France
PRINCIPLE III. ANALYTICAL PERFORMANCE WITH
TANDEM MEASUREMENTS IS NOT IMPROVED
WITHOUT SIGNIFICANT TRANFORMATION OF IONS BETWEEN STAGES
WHICH FORM OF MOBILITY SPECTROMETRY?
Asymmetric Waveform 1.1 MHz 30KV/cm +
-
1 to 10 ms RESIDENCE TIME
R.A. Miller, G.A. Eiceman, E.G. Nazarov and A.T. King, Sensors and
Actuators B. Chemical 2000, 67, 300-306.
SMALL ION MOBILITY ANALYZERS*
*See Owlstone Nanotech for very small analyzers
+K
COMPENSATION VOLTAGE (V)
4
3
-20 -15 -10 -5 0 5 10
1
2
PROTON BOUND DIMER
-K
PROTONATED MONOMER
MOBILITY SPECTRUM : 1 to 3 s SCAN TIMES
DISPERSION PLOTS: Ion evaluation from field
dependence of mobility: Time: 1 to 3 min. S
ep
ara
tio
n V
olt
ag
e
Compensation Voltage
CLOSE OBJECTIVE OF DMS DMS: Fast selectivity
based on E/N dependence. Time: 10 ms
DMS 1 DMS 2
Sep
ara
tio
n V
olt
ag
e
Compensation Voltage
SV 1000 V
NOT ONLY K(E/N)-ALSO DIFFERENCES IN K(E/N)
-16 -12 -8 -4 0
600
700
800
900
1000
1100
Compensation Voltage, V
Se
para
tio
n V
olta
ge
, V
0.4120
0.4500
0.4750
0.5800
0.6430
0.7007
0.7585
0.8163
0.8740
methanol
IPA
butanol
ethanol
clusters
0.5 mm
DMS 1 Electronics &
PC Control
DMS 2 Electronics & PC
Control
Gas Flow Control with
Sample
Faraday Plate &
Amplifier
5 mm
CVDMS1
SVDMS1
Det (-)
Det (+)
SVDMS2
CVDMS2
2 mm
BLOCK DIAGRAM of DMS/DMS WITH
FARDAY PLATE DETECTORS
0.5 mm
GC 63Ni
ALL PASS (no Separation Voltage) SCANNING CV (& SCAN Separation V)
FIXED CV (at a Separation Voltage) SCANNING CV (at a Separation Voltage)
FIXED CV (at a Separation Voltage) SCANNING CV (at SV + 50 V)
FIXED CV (at a Separation Voltage) FIXED CV (at SV + 50 V)
DMS 1 DMS 2
Gas
Chromatograph
STUDIES AND MEASUREMENTS ON
SELECTIVITY AND SPEED OF RESPONSE FOR
DMS DMS
GC DMS/DMS SEPARATION OF 23 CONSTITUTENTS
1 2 3 4 5 6 7 8 9 10
0.5
0.6
0.7
0.8
0.9
1.0
1.1
ALL PASS (600 V) SCANNING CV (at fixed SV, -12 to 2 V)
DMS 1 DMS 2
Retention Time (min)
Inte
nsity, V
-12 -10 -8 -6 -4 -2 0 2
1
2
3
4
5
6
7
8
9
10
11
Compensation Voltage (V) for DMS2
Rete
ntion T
ime (
min
)
0.3650
0.4888
0.6125
0.7362
0.8600
0.9838
1.107
1.231
1.355
Separation Voltage 700V
GC DMS DMS SEPARATION OF 23 CONSTITUTENTS
-15 -12 -9 -6 -3 0 3 6
1
2
3
4
5
6
7
8
9
10
11
Compensation Voltage (V) for DMS2
Rete
ntion T
ime (
min
)
0.3600
0.4607
0.5615
0.6623
0.7630
0.8638
0.9645
1.065
1.166
Separation Voltage 1000V
GC DMS DMS SEPARATION OF 23 CONSTITUTENTS
1-Hexanol DMMP
5-5-10 0
Compensation voltage, V
-15
1500
1200
900
600
Se
pa
ratio
n v
olta
ge
, VDMS1
DMS2
5-5-10 0
Compensation voltage, V
-15
1500
1200
900
600
Se
pa
ratio
n v
olta
ge
, V DMS2
DMS1
DISPERSION PLOTS FOR TWO CONSITUTENTS
IN MIXTURE. SELECT TWO PAIRS FOR:
SV AND CV
Retention time, min
Inte
nsity,
V
2 4 6 8 10
0.6
0.8
1.0
0.4
0.5
0.5
0.6
1-hexanol
DMMP
SIGNAL VS CHEM NOISE BY DMS/DMS ALONE
Iso-propanol
Acetone
ION EXTRACTION AS GC PEAKS MERGE:
CONTROL
Extracted ion chromatogram
SV1=600V, CV1= -2.4V
SV2=550V;
-1.8V
Extracted ion chromatogram
SV1=600V, CV1= -0.5V
SV2=550V;
-0.8V
Total ion chromatogram
Retention Time (min)
Inte
nsity, V
1.4 2.2
Iso-propanol Acetone
ION EXTRACTION AS GC PEAKS MERGE:
MERGED
Extracted ion chromatogram
SV1=600V, CV1= -2.4V
SV2=550V;
-1.8V
Extracted ion chromatogram
SV1=600V, CV1= -0.5V
SV2=550V;
-0.8V
Total ion chromatogram
Retention Time (min)
Inte
nsity, V
0.6 1.2
EARLY CONCLUSIONS
B. Alpha function alone contained orthogonality
enough to select an ion over “chemical noise”.
A. DMS DMS with fixed SV and CV provide
response times near 100 ms ----> 10ms (in theory).
C. Results suggest demands on mass
spectrometers may be lessened by ion “handling”
outside vacuum chamber.
LONG OBJECTIVE OF DMS DMS: High
Selectivity by ion modification at ambient
pressure
DMS 1 DMS 2
Fragmentation by E
Formation of clusters
Charge stripping
Other
Fragmentation by hv
DMS1 DMS2
a
b
Sample gas flow 1.5 L/min
Dopant gas flow 0.2 L/min
c
Flo
w v
elo
cit
y,
m/s
COMSOL FLOW MODELING IN DMS/DMS
(FLOW DYNAMICS TEST)
Flow velocity map
Flow velocity map
Pressure map
ORTHOGONALITY WITH REAGENT CHEMISTRY Methyl salicylate and isopropanol
M M
IPA
1) MO2-(H2O)n + mC3H7OH M + nH2O + O2
- (C3H7OH)m
2) MO2-(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
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
O2-(C3H7OH)m
O2-(C3H7OH)m
(-3;-16)
(-10;-16)
CVDMS2, V
ELECTRIC FIELD FRAGMENTATION OF GAS
IONS AT AMBIENT PRESSURE
DMS 1 DMS 3 MS/MS
MS/MS
Final Design
Stage 1 Studies
DMS 2
DMS
FIELD DIRECTED DISSOCIATION &
FRAGMENTATION OF GAS IONS
Compensation Field (Td)
-4.92 -3.28 -1.64 0 1.64
Sep
ara
tio
n F
ield
(T
d)
59
117
176
M2H+
F+
RIP
MH+
At 100°C
MH+
F+
M2H+
0.00
0.50
1.00
80 110 139 168
DMS
Separation Field (Td)
No
rma
lize
d I
nte
nsit
y
59 94 129 164 0.00
0.50
1.00 F+
M2H+
MH+
DMS/MS
DMS MS OF M2H+ AND CID OF MH+
Rela
tive I
nte
ns
ity
50 100 150 200
43 61
97
m/z
55 73
121
139
205 (a) 70 Td
97
121 79 73
205 (b) 117 Td
97
79
(c) 164 Td
40 60 80 100
79
73: (H2O)4H+
55: (H2O)3H+
97: CH3COOH2+(H2O)2
79: CH3COOH2+(H2O)
61: CH3COOH2+
43: CH3CO+
Fragment Ions
205: M2H+
139: MH+ (H2O)2
121: MH+(H2O)
Ions of Ester
Reactant ions
(d) CAD of m/z 97
POSSIBLE FRAGMENTATION PATHWAY:
THROUGH THE PROTONATED MONOMER
energy changes were computed and compared favorably to literature
values; Can. J. Chem. 57 (1979) 2996-3004
87
117
147
30 70 110 150
Temperature (°C)
Sep
ara
tio
n F
ield
(T
d)
144
130
116
102
116
Ethyl hexanoate
Ethyl Propionate 102
Propyl
propionate
130
144
Propyl butyrate
-0.68 + 0.06 Td/°C
or
1.5°C/Td Acetates
E/N THRESHOLDS FOR FIELD INDUCED
REACTIONS AS ƒ(TEMP)
CONCLUSIONS
A. DMS DMS is demonstrated as a comparatively simple
and method with consistent control of ion behavior
B. DMS DMS with fixed SV and CV
provide response with selectivity
and response time at 100 ms----
>10ms.
C. Routes to addition of
orthogonality through ion
chemistry demonstrated in a few
examples all at ambient pressure.
ACKNOWLEDGEMENTS
Financial Support
National Science Foundation, Award
No.
CHE-1306388
Material Support:
CHEMRING Detection
Systems