A large suite of illicit drug samples were analyzed using IMS to evaluate the selectivity and sensitivity of the technique. The sample suite represents over 80% of the samples reported by state and federal forensic laboratories over the past 7 years, and contains complex multi-drug and drug/excipient combinations. IMS was found to provide reliable qualitative analyses for the majority of the samples, with the exception of cannabis samples. The sensitivity of IMS was tested by preparing standard test materials using solutions delivered both by pipette and by drop-on-demand inkjet printing. Inkjet printed test samples containing cocaine at levels near the detection limit were evaluated in an intercomparison with the Drug Enforcement Agency. This program supports the widespread deployment of IMS by local law enforcement, US Customs and Border Protection, the US Coast Guard, the National Guard, and federal and state correctional facilities.
A suite of samples representative of the majority of forensic drug exhibits was developed by evaluating published reports, including those by the National Forensic Laboratory Information System (NFLIS). This comprehensive suite includes 10 illicit drugs and 8 excipients in various combinations. The reduced mobilities of all analytes were measured over an extended period of time and compared with the size of the instrument detection windows. Peak overlaps were identified and evaluated with respect to detection reliability. The excipient levels that resulted in false negatives for the illicit drugs were also determined. Samples included materials prepared from reagent grade chemicals and actual forensic exhibits from the Montgomery County Police Department and the DEA (Figure). Test samples containing cocaine at multiple levels near the detection limit were prepared by inkjet printing and were characterized by IMS to determine average peak heights. The samples were also analyzed on a similar instrument at the DEA, and those data agree with NIST results.
Development of a sample suite representing the majority of forensic drug exhibits
Evaluation of IMS for this suite of samples
Preparation of inkjet printed test samples of cocaine at levels near the detection limit, and evaluation of these materials in an intercomparison with the DEA