Real-time monitoring of TATP released from PDMS-based canine training aids versus bulk TATP using DART-MS

Abstract

Direct analysis in real time-mass spectrometry (DART-MS) was used to explore the behavior of vapor released from triacetone triperoxide (TATP) versus an absorption-based canine training aid sometimes called a polydimethylsiloxane (PDMS) polymer odor capture and release (POCR) system. The results compare dissipation from the source to the instrument (in minutes), steady state signal intensity (i.e. approximate relative amounts), and dissipation of the odor after removing the source (also in minutes). Several parameters were tested: reproducibility between POCRs, TATP versus TATP with a lid (containing 13 drilled holes), distance from the detector, heights of the source, concealment, purposeful air disturbances, blanks, and containment systems.In general, the PDMS-based training aid behaved similarly to the TATP with a 13-hole lid, which is the aid most often used by the FBI’s National Canine Improvised Explosives Detection Program. Results shows that the PDMS-based training aids are reproducible and reliable at steady state as a vapor release system. As expected, signal was decreased given increased distance from the DART interface for all sample types, when using the odor-restricting lid with the 1 g TATP sample, when all samples were placed at height, and when using a cotton bag as a method of concealment. Despite having no direct correlation, these results support anecdotal canine evidence since canine handlers tend to report that their dogs have more difficulty finding training aids within those same parameters. Further, adding purposeful air disturbances had a larger effect on signal intensity for 1 g TATP than on the PDMS-based training aid. Finally, adding a masking odor at the DART interface decreased detection of TATP regardless of the vapor source, but did not fully diminish it. This too agrees with canine handler reports and previous research, where dogs may have a more difficult time locating odors in the presence of high background.This is the first report of its kind to use real-time detection to characterize vapor release and dissipation from a biosensor training aid in comparison to the corresponding true material it intends to replace. By using the three phases of odor release (saturation, steady state, and depletion), the study investigates the effects of several ambient parameters on TATP volatile detection from true material and the PDMS-based training aid.