A new approach to reduce false positive response commonly encountered in the field when drugs and explosives are detected is reported for an electrospray ionization high performance ion mobility spectrometry (ESI-HPIMS). In this work, we report on a new parameter called conditional reduced mobility (CRM). We found that the CRM was capable of differentiating between real drugs and explosive ions from that of a false positive peak and may help to reduce false positive rates. Certified reference materials of drugs and explosives samples were prepared at different concentrations and analyzed with the ESI-HPIMS. Interference were prepared as follows: a small amount of the interference was initially dissolved in 10 mL HPLC grade methanol. 10 µL of filtered sample was then withdrawn and transferred to a 2.0 mL micro-centrifuge tube and diluted to 1 mL total volume with ESI solvent. Reduced mobility for target compounds reported were reproducible to within 2% for ESI-HPIMS. The estimated resolving power for the ESI-HPIMS used in this study was 61 ± 0.22. Conditional reduced mobility introduced in this paper show differences between target compounds and false positive peaks as high as 74% as was the case for cannabidiol and interference #1 at 70 µs gate pulse width. The calculated CRM (Kc) demonstrated that identity differentiation can be achieved for drugs and explosives and other interference peaks by taking advantage of different gate pulse widths in an IMS system. Thus, Kc, as introduced in this presentation provides a way to rapidly predict where the optimal CRM of an IMS will be and what it will be (or at least what it can be). The CRM or Kc value is a measure of the identity of an ion; a new parameter that may be applied to help aid IMS devices with false positive issues.

Drugs and explosives identify differentiation in ion mobility spectrometry

2019 Spring National Meeting

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