Nitrogen direct analysis in real time time-of-flight mass spectrometry (N2 DART-TOFMS) for rapid screening of forensic drugs.

Abstract

Over the last ten years, helium direct analysis in real time time-of-flight mass spectrometry (He DART-TOFMS) has become an established technique in rapid screening of forensic drugs to decrease the time necessary to triage forensic drug cases, therefore contributing to backlog reduction and more timely criminal prosecution. Recently, we demonstrated that N2 DART was able to efficiently ionize all polar compounds except for a few extremely small ones such as methanol and acetonitrile. Therefore, N2 DART-TOFMS should be a suitable technique for rapid screening of forensic drugs. Nitrogen direct analysis in real time time-of-flight mass spectrometry (N2 DART-TOFMS) was performed using a JEOL AccuTOF mass spectrometer with an IonSense DART-100 ion source. A 3-min analytical protocol was used for the analysis of each sample. Sample introduction was accomplished by moving the closed end of a melting point capillary where approximately 1 μL sample solution was deposited or the exposed inside of a freshly cut tablet across the N2 gas stream between the DART-100 ion source and orifice 1 of the AccuTOF. Ten commonly abused drugs, eight synthetic cannabinoids and four controlled prescription drugs (CPDs) were analyzed. The limit of detection (LOD) was determined to be approximately 10 μg/mL or 10 pg in quantities. All drugs at the LOD level were positively identified using their [M + H]+ ions with mass errors less than 5 mDa. The identification were further supported by in-source fragment ions and characteristic N2 DART ions that are not commonly generated by He DART, e.g. [M + H + O]+ and [M + H + 2O]+ ions. It was concluded that the 3-min analytical protocol could be utilized in the analysis of seized drugs in the form of tablets and powders or prepared in solution. In consideration that N2 is readily available in the air and He is a non-renewable resource, N2 DART-TOFMS is a greener, cheaper and more convenient alternative to He DART-TOFMS in rapid screening of forensic drugs.