Differential Mobility Spectrometry
Differential Ion Mobility Spectrometry
Field Asymmetric Ion Mobility Spectrometry ...
DMS takes atmospheric pressure generated ions (say from electrospray or your brand of atmospheric pressure chemical ionization) and selectively transmits them through a channel based on characteristic ion mobility behavior. A gas flow is created by a vacuum draw (sometimes from a mass spectrometer) between two parallel electrodes. Across the electrodes, we apply an electrical waveform alternating between high and low voltages that only allows a particular ion of interest through. Depending on the voltages applied, we can change the ion of interest which has a certain "differential mobility". When these filtered ions are sent downstream to a mass spec, we can clean up sample mixtures to empower the mass spec. Theresa likes the analogy of an extraction step before chromatographic analysis.
In our work, we've focused on drug forensics (amphetamines, opioids) and nuclear forensics (radionuclides and analogs). We have an old Sionex-based unit that we coupled to commercial atmospheric pressure inlet-based mass spectrometers, previously an Agilent 6230 (a TOF) and, more recently, a Thermo LTQ (a linear ion trap). The most useful thing when coupling to mass spec is primarily isobaric ions, things with the same nominal molecular weight and therefore m/z in the mass spectrum.