Getting a Whiff of Crime: The Chemistry Behind Detection of Illicit Substances by a New Sniffer Dog

To combat the constantly shifting threat related to the trafficking of illicit drugs and terrorism and meet Law Enforcement Agencies (LEAs) operational requirements, the exploitation of the latest scientific and technical advances is key. A valid alternative to the detection technologies currently used/explored by UK and International markets, is the CRIM-TRACK sniffer device, which allows detection of multiple illicit substances in a non-destructive, rapid, and accurate manner. The CRIM-TRACK sniffer includes a colourimetric sensor system (Microchip, Figure 1) consisting of chromic dyes reacting to vapour traces of illicit substances (Analytes).The aim of this PhD project is to further develop the CRIM-TRACK sniffer device’s colourimetric sensor through chemical analysis of the interaction between analyte and dye molecules. Responsive (Colour changing) and non-responsive dyes from the current colourimetric microchip for the analyte of interest are determined through detection experiments using the CRIM-TRACK sniffer. The detection mechanisms of four analytes – a selection of chemical precursors and controlled drugs – with two families of dyes, diazobenzenes and sulfonephthaleins, have been ascertained. This is achieved by applying analytical techniques such as Nuclear Magnetic Resonance and UV-Vis Spectrophotometry and comparing the data produced by analyte:dye mixtures and their single components. Evaluation of these mixtures is aided by comparison of experimental data against modelling data produced by colleagues at Sheffield Hallam University. Understanding the detection mechanisms allows the identification and selection of other responsive dyes for improvement of the current microchip and the design of scenario specific microchips.