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Department of Chemistry Homeland Security

Ion Mobility Spectrometry (IMS) is chemical trace detection technique used for contraband substance detection since the 1970’s. Since then, a community of researchers has developed the technique so that commercial systems:

  • analyze a sample in less than 5 seconds;
  • easy to operate in the field;
  • sub ppb detection limits for contraband substances such as explosives, chemical warfare agents, and illicit drugs;
  • operate at atmospheric pressure with air as the carrier gas.

Consequently, commercial IMS systems have been deployed across the world at security checkpoints.

Our research focuses on using ion mobility-mass spectrometry to detect contraband substances. This hybrid technique offers a distinct advantage over both IMS and MS alone: the ability to simultaneously separate samples by both mobility and mass. This two-fold separation mechanism greatly decreases the likelihood of a mass or mobility interferent masking the signal of the analyte of interest. The ability to separate in two dimensions (2D) is extremely powerful in complex, real-world samples where matrix effects may significantly inhibit the detection of trace amounts of contraband material.

Currently, we are working on applications of IMMS for nuclear forensics and increasing the sensitivity and selectivity of IMMS for explosives and chemical warfare agent detection.

2D Mobility-Mass Spectrum of black powder
2D Mobility-Mass Spectrum of black powder. The one dimensional mobility spectrum is shown on the right margin of the two dimensional spectrum. The one dimensional mass spectrum is shown on the top margin of the two dimensional spectra. Horizontal lines centered about 8,200 μs and 11,000 μs show possible fragmentation of the m/z 128 and m/z 193 species in the mass spectrometer interface, respectively. A linear Mobility-Mass Correlation Curve (MMCC) connects m/z 128, m/z 160, and m/z 193, indicating the relationship of the response ions’ mobility and mass peaks to each other. See Anal. Chem. 2010, 82, 387–393.