Forensic and toxicological applications of Franz diffusion cells assessed by gas chromatograhy mass spectrometry and ion mobility spectrometry.

The first portion of this work evaluated the efficacy of ion mobility spectrometry (IMS) as a tool for determining remediation success at clandestine methamphetamine laboratory sites. Specifically, limits of detection (LOD), limits of quantitation (LOQ), and matrix effects were investigated as relevant to typical remediation sites and situations. The recoveries of pseudoephedrine and methamphetamine from a range of various surfaces likely to be found in a clandestine laboratory were examined. Portable IMS instruments with thermal desorption were found to be a reliable tool for evaluating the degree of remediation if sufficient procedural and instrumental controls are put into place. In general, detection limits were in the same range as state guidelines as well as laboratory methods using gas chromatography mass spectrometry (GC/MS) and liquid chromatography mass spectrometry (LC/MS). Direct vapor sampling can be used to detect high levels of methamphetamine and potential interferences, but cannot approach the detection limits needed for evaluation of remediation efforts. IMS cannot be used alone to determine the efficacy of remediation efforts; final confirmation using laboratory instrumentation is essential. For the purpose of this study, typical field settings of the IMS were used and the conditions were not optimized. The second portion of this research focused on the ability of organic gunshot residue (OGSR) to be dermally absorbed after discharging a firearm. Previous studies in our research group have demonstrated that the persistence of compounds, such as diphenylamine (DPA), from hand swabs of shooters using IMS was around 3 – 4 hours and that secondary transfer was unlikely. In vitro studies with medical grade silicone were conducted using Franz diffusion cells (FDCs). A novel IMS method was developed for the in vitro analysis of selected OGSR compounds. A comprehensively validated GC/MS selected ion recording (SIR) procedure was developed for the quantitative analysis of the dermal absorption of selected OGSR compounds. In the validation tests, linearity, range, accuracy, intra- and inter-day precision, LOD, LOQ, and selectivity were tested and explained in detail. Different commercially available sampling media were evaluated for their potential use as a swab for the collection of selected OGSR compounds from the back of a shooter’s gun hand. The most efficient swab was used to determine the concentration of OGSR on the back of a shooter’s gun hand after discharging a firearm. A solution of a similar concentration was prepared for use in the in vitro experiments. The results from the in vitro studies demonstrated that OGSR has the ability to be dermally absorbed, which could open up new avenues in casework studies to differentiate shooters from non-shooters