Differential mobility spectrometry with nanospray ion source as a compact detector for small organics and inorganics.

Electrospray ionization (ESI) is an important tool in chemical and biochemical survey and targeted analysis in many applications. For chemical detection and identification electrospray is usually used with mass spectrometry (MS). However, for screening and monitoring of chemicals of interest in light, low power field-deployable instrumentation, an alternative detection technology with chemical selectivity would be highly useful, especially since small, lightweight, chip-based gas and liquid chromatographic technologies are being developed.

Planar differential mobility spectrometer as a pre-filter for atmospheric pressure ionization mass spectrometry.

Ion filters based on planar DMS can be integrated with the inlet configuration of most mass spectrometers, and are able to enhance the quality of mass analysis and quantitative accuracy by reducing chemical noise, and by pre-separating ions of similar mass. This paper is the first in a series of three papers describing the optimization of DMS / MS instrumentation. In this paper the important physical parameters of a planar DMS-MS interface including analyzer geometry, analyzer coupling to a mass spectrometer, and transport gas flow control are considered.

Detection of Radiation-Exposure Biomarkers by Differential Mobility Prefiltered Mass Spectrometry (DMS-MS).

Technology to enable rapid screening for radiation exposure has been identified as an important need, and, as a part of a NIH / NIAD effort in this direction, metabolomic biomarkers for radiation exposure have been identified in a recent series of papers. To reduce the time necessary to detect and measure these biomarkers, differential mobility spectrometry - mass spectrometry (DMS-MS) systems have been developed and tested. Differential mobility ion filters preselect specific ions and also suppress chemical noise created in typical atmospheric-pressure ionization sources (ESI, MALDI, and others).

Selection and generation of waveforms for differential mobility spectrometry.

Devices based on differential mobility spectrometry (DMS) are used in a number of ways, including applications as ion prefilters for API-MS systems, as detectors or selectors in hybrid instruments (GC-DMS, DMS-IMS), and in standalone systems for chemical detection and identification. DMS ion separation is based on the relative difference between high field and low field ion mobility known as the alpha dependence, and requires the application of an intense asymmetric electric field known as the DMS separation field, typically in the megahertz frequency range. DMS performance depends on the waveform and on the magnitude of this separation field.

Chemical effects in the separation process of a differential mobility/mass spectrometer system.

In differential mobility spectrometry (also referred to as high-field asymmetric waveform ion mobility spectrometry), ions are separated on the basis of the difference in their mobility under high and low electric fields. The addition of polar modifiers to the gas transporting the ions through a differential mobility spectrometer enhances the formation of clusters in a field-dependent way and thus amplifies the high- and low-field mobility difference, resulting in increased peak capacity and separation power. Observations of the increase in mobility field dependence are consistent with a cluster formation model, also referred to as the dynamic cluster-decluster model.

Control of chemical effects in the separation process of a differential mobility mass spectrometer system.

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.

Pressure effects in differential mobility spectrometry.

A microfabricated planar differential ion mobility spectrometer operating from 0.4 to 1.55 atm in a supporting atmosphere of purified air was used to characterize the effects of pressure and electric field strength on compensation voltage, ion transmission, peak width, and peak intensity in differential mobility spectra.