Control of Chemical Effects in the Separation Process of a Differential Mobility Mass Spectrometer System

Abstract

Differential mobility spectrometry (DMS) separates ions on the basis of the difference in their migration rates under high versus low electric fields. Several models describing the physical nature of this field mobility dependence have been proposed but emerging as a dominant effect is the clusterization model sometimes referred to as the dynamic cluster-decluster model. DMS resolution and peak capacity is strongly influenced by the addition of modifiers which results in the formation and dissociation of clusters. This process increases selectivity due to the unique chemical interactions that occur between an ion and neutral gas phase molecules. It is thus imperative to bring the parameters influencing the chemical interactions under control and find ways to exploit them in order to improve the analytical utility of the device. In this paper we describe three important areas that need consideration in order to stabilize and capitalize on the chemical processes that dominate a DMS separation. The first involves means of controlling the dynamic equilibrium of the clustering reactions with high concentrations of specific reagents. The second area involves a means to deal with the unwanted heterogeneous cluster ion populations emitted from the electrospray ionization process that degrade resolution and sensitivity. The third involves fine control of parameters that affect the fundamental collision processes, temperature and pressure.

A determination of the effective temperatures for the dissociation of the proton bound dimer of dimethyl methylphosphonate in a planar differential mobility spectrometer

“…This rate of change of temperature with voltage is consistent with the value of 0.2 K V −1 estimated by Schneider et al for the dissociation reaction SF À 6 ! SF À 5 þ F at about 24,000 V cm −1 [39]. When T eff is plotted as a function of (E/N) 2 a linear relationship is also observed, as seen in Fig.…”

Three-dimensional enhanced lipidomics analysis combining UPLC, differential ion mobility spectrometry, and mass spectrometric separation strategies

“…The ability of DMS to resolve lipid isobars lies in its ability to separate molecules based on their chemical properties ( 24,25,29 ) rather than size and shape alone, factors that are the basis for separation by ion mobility in drift tubes ( 19 ). The length of the DMS cell is short (3 cm) compared with more traditional ion mobility drift tubes, as the resolution lies in the separation of molecules based on their differential mobilities under oscillating high and low electrical fi elds.…”

“…Under high electrical fi elds, the modifi er declusters from the ion. Hence, the net effect of the modifi er is enhancement of the differential mobility under the oscillating electrical fi eld ( 25,29 ). This technique differs from traditional ion mobility spectrometry wherein molecules are separated by their crosssectional area, which is related to their shape and size (and hence molecular weight), rather than chemical effects ( 30 ).…”

Pulsed electron beams in ion mobility spectrometry

“…These sources were also examined in order to have non-radioactive alternatives because of the technical, organizational and related financial complications that accompany the application of radioactive substances. Regarding the voltage schemes, in particular high-field asymmetric field ion mobility spectrometry (FAIMS) (Klaassen et al 2009, Shvartsburg et al 2009, Schneider et al 2010, Barnett and Oullette 2011 has attracted a lot of interest in recent years.…”