DMS-IMS2, GC-DMS, DMS-MS: DMS hybrid devices combining orthogonal principles of separation for challenging applications

Abstract

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-IMS 2 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-IMS 2 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, H 2 S 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. Differential mobility spectrometry 1,2,3 (DMS) is recognized as a powerful tool for separation and characterization of gasphase ions. In DMS, ions are distinguished by the difference between mobilities at high and low electric fields, exploiting the fact that ion mobility values depend on the applied field strength. Developed and refined over the past decade, differential mobility spectrometry (DMS) is also known as field-asymmetric waveform ion mobility spectrometry (FAIMS) 4 (FAIMS is often used to refer to a coaxial configuration). Several configurations of DMS analyzers have shown response to trace amounts of chemical species including explosives 5,6 , chemical warfare agents and simulants 7 , volatile organic compounds 8 , and a variety of other organic and inorganic substances 9 . Hybrid DMS techniques such as GC-DMS 10 , DMS-IMS 11 , D...

Quantitative determination of n-alkanethiols in air and in a blended gas mixture of methane with air by gas chromatography/differential mobility spectrometry

“…A Hewlett-Packard model 5721A gas chromatograph was equipped with a split-splitless injector, 25 m SP 2300 capillary column (Supelco, Bellefonte, PA), and a DMS analyzer (model SDP-1, SIONEX Corporation, Bedford, MA) as the detector [29,37]. Instrument parameters included: inlet pressure, 10 psig; split ratio, 200:1; and carrier gas, nitrogen purified using 5Å molecular sieve.…”

“…Differential mobility spectrometry (DMS) was shown early in its development to show favorable response to thiols [27] and the technology for DMS has matured rapidly from inception as a micro-fabricated analyzer [28] to refined commercial analyzers with GC inlets today [29]. Analyzers based on DMS have practical attractions from high portability and convenient operation, as do hand-held mobility spectrometers, and additional features of simultaneous detection of positive and negative ions and continuous monitoring or filtering of ions permitting selective ion monitoring.…”

Separation principle and Monte Carlo studies for differential mobility spectrometry

“…All simulations were performed on a laptop computer equipped with Intel Core i7 2.67 GHz CPU, 4.0 GB RAM using Windows 7 Enterprise 64 bit operating system. Validation experiments were done with a microanalyzer GC-DMS [2,23,24].…”

“…Since its first publication in 1991 [1], differential mobility spectrometry (DMS), also known as field asymmetric ion mobility spectrometry (FAIMS), is increasingly used as an analytical method, either as stand-alone detectors of trace chemicals or as selective filters for mass spectrometry (MS) [2][3][4][5][6]. In conventional ion mobility spectrometry (IMS), ions are separated according to their mobility.…”

Transient simulation of moving ion clouds in time-of-flight ion mobility spectrometers operating with DC and AC fields

“…Combining FAIMS and drift tube IMS will take advantage of complementary data on a given ion species and enhance the selectivity in comparison with stand-alone FAIMS or drift tube IMS. In [12] two drift tube IMS are coupled to a FAIMS system. However, the drift tube IMS can only analyze the ions passed through the FAIMS at a given time.…”