Theresa Evans-Nguyen Research Group
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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. 
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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.
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 ​

Ife_ASMS_2017
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Ife_HEMS_2017
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Ife_Asilomar_2016
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  • Home
  • TEAM
  • RESEARCH
    • Drug Forensics
    • Stable Isotope Analysis
    • HDX
    • SAWN
    • Liposomes
    • Differential Mobility Spectrometry
  • Publications
  • News
  • Lab Life