Differential Mobility Spectrometry
Differential Ion Mobility Spectrometry
Field Asymmetric Ion Mobility Spectrometry ...
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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.
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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.
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Nathan has been working on this project since 2018 and has been investigating methods involving the incorporation of a vapor phase modifier to aid in separations. Primarily driven by a clustering-declustering phenomenon involving a change in mobility from the high to low field, these incorporations have proven successful in separating isobaric, and when using a chiral modifier, even enantiomeric ion pairs.
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Separation of chiral amino acid enantiomeric pair achieved from through addition of chiral vapor phase modifier
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| Ife_ASMS_2017 |
| Ife_HEMS_2017 |
| Ife_Asilomar_2016 |
