Two-temperature preparation method and visualization of PDMS-based canine training aids for explosives

Abstract Training aids based on vapor capture-and-release into a flexible polymer, polydimethylsiloxane (PDMS), have proven successful in canine detection of explosives that have volatile or semi-volatile odorants. To enhance the rate of odor capture for less volatile targets, two temperatures are used for aid preparation. By using an elevated temperature for the target explosive, the amount of vapor is enhanced, increasing the production of the characteristic odor profile. The polymeric adsorbent is maintained at a cool temperature, favoring vapor capture. The success of this two-temperature approach is demonstrated for the low volatility explosive TNT using SPME (solid-phase microextraction) headspace analysis. In addition, the effect of using two temperatures on preparing training aids based on TNT and its more volatile impurities 2,4-DNT and 2,6-DNT are evaluated in canine trials. A protocol to minimize the non-target odors in the polymer is presented. Furthermore, schlieren videography helps to visualize the transport behavior of such heavier-than-air targets released by the training aids.