Proceedings Article | 17 April 2008
KEYWORDS: Ions, Chemical analysis, Spectroscopy, Sensors, Biological research, Ionization, Electrodes, Explosives, Signal to noise ratio
Sionex Differential Mobility Spectrometer (DMS) sensors can be used as standalone detectors in many applications
because of their outstanding sensitivity and selectivity. However, in applications like field screening for toxic chemicals
and explosives, the number of possible interferents may be so high that additional separation becomes useful for
identification and for quantitative measurement. For these cases, we have developed several different hybrid
technologies. (1) DMS-IMS2 integrates bipolar differential mobility ion filtration with IMS drift time measurement in
IMS drift tubes, one tube for each ion polarity. (2)The Sionex
GC-DMS (microAnalyzer) combines a pre-concentrator, a
rapid and selective GC column that operates at high temperature in an air recirculation loop, and DMS ion filtration and
detection. (3) Sionex DMS-MS interfaces have been developed for several types of mass spectrometers, and dramatically
improve mass spec performance by filtering out unwanted species to reduce chemical noise and improve measurement
accuracy.
The Sionex DMS-IMS2 first uses DMS to select positive and negative ions based on ion mobility variation with field
(the α(E) function), then uses paired IMS sections to measure the low field mobility (K(0)). DMS separation depends on
many properties including the distribution of internal charges, rigidity, and clustering. The IMS drift times depend on
molecular size and conformation at low fields. A number of applications of this technology will be described, including
CWA's, TIC/TIM, and explosives.
The Sionex microAnalyzer GC-DMS system combines sophisticated preconcentration, thermal desorption, GC
temperature ramping, and DMS separation and detection in a compact, portable and field-deployable package. The list of
applications for this technology is growing rapidly, currently including CWAs, BTEX, H2S and mercaptans, and others.
Sionex DMS-MS interfaces are being used to make quantitative measurements of biomarkers, including breath markers,
biofluid markers, and cancer-linked agents. DMS-MS improves the performance / cost tradeoff for the mass
spectrometer, greatly speeds analysis compared to LC-MS, and maintains measurement accuracy.
