Ambient pressure thermal desorption ionization mass spectrometry for the analysis of substances of forensic interest.

The large backlog of forensic samples needing chemical analysis requires new tools with high specificity, throughput, and reliability. Mass spectrometric techniques have the specificity and reliability necessary for identification, but often require sample preparation before analysis. The growth of ambient pressure ionization techniques has the capability to reduce the need for lengthy preparation. This report presents one possible technique, ambient pressure thermal desorption ionization mass spectrometry, which could prove to be useful to the forensic science community. Example mass spectra for several explosive compounds and illicit drugs obtained from liquid and bulk samples with almost no sample preparation are presented. The use of the technique for quantitative analysis is also addressed.

Evaluation of C60 secondary ion mass spectrometry for the chemical analysis and imaging of fingerprints.

The feasibility of using C60(+) cluster primary ion bombardment secondary ion mass spectrometry (C60(+) SIMS) for the analysis of the chemical composition of fingerprints is evaluated. It was found that C60(+) SIMS could be used to detect and image the spatial localization of a number of sebaceous and eccrine components in fingerprints. These analyses were also found to not be hindered by the use of common latent print powder development techniques. Finally, the ability to monitor the depth distribution of fingerprint constituents was found to be possible - a capability which has not been shown using other chemical imaging techniques. This paper illustrates a number of strengths and potential weaknesses of C60(+) SIMS as an additional or complimentary technique for the chemical analysis of fingerprints.

Measurement of drug facilitated sexual assault agents in simulated sweat by ion mobility spectrometry.

Ion mobility spectrometry has found widespread use for the detection of explosives and illicit drugs. The technique offers rapid results with high sensitivity and little sample preparation. As such, it is well suited for field deployed screening settings. Here the response of ion mobility spectrometers for three drug-facilitated sexual assault (DFSA) agents - flunitrazepam, ketamine, and MDMA - and related metabolites has been studied in the presence of a simulated sweat. While all three DFSA agents present certain challenges for qualitative identification, IMS can provide useful information to guide the early treatment and investigation of sexual assault cases. Used as a presumptive test, the identification of DFSA agents would later require confirmatory analysis by other techniques.

Behavior and evaluation of tetraalkylammonium bromides as instrument test materials in thermal desorption ion mobility spectrometers.

Ion mobility spectrometers have found widespread use for the screening of explosives, chemical warfare agents, and illicit drugs. These instruments often rely on drift-time calibrants to perform qualitative identification. Such calibrants are suitable to determine the reduced mobility of compounds, but may not necessarily provide information on instrument performance. These calibrants are often internal and behave in a fashion similar to that of analytes in terms of sensitivity to a variety of instrumental and environmental variations. Ideally, test materials used to evaluate instrument performance would be insensitive to these changes. Current calibrants are sometimes not designed to satisfy these requirements, and although several instrument test materials are also in use, a consensus has not been reached on best practices. A homologous series of tetraalkylammonium salts has been proposed as one alternative instrumental test material set and has been successfully used for electrospray ion mobility spectrometry (IMS)-MS experiments. This study extends these analyses to thermal desorption IMS instruments. The reduced mobility (K0) values for these compounds, measured on a thermal desorption IMS instrument, are reported and are similar to those reported for electrospray IMS. The variability of daily instrument response to these compounds is small, further supporting their use as test materials. The ionization behavior and thermal profile of the compounds in the thermal desorption process are discussed.