The development of an electrochemical sensing device for controlled drugs.

Forensic chemists can be faced with a wide array of substances to test when attending clandestine drug manufacture crime scenes. Whilst many techniques exist at their disposal - such as chemical colour test reagents and immunoassays - these methods are at best semi-quantitative and often subject to false positives. Electrochemical methods of detection offer a potential solution to this problem, as the equipment is portable, cheap and robust. The analysis is quantitative and, if the electrode/electrolyte combination is designed properly, it can be extremely sensitive and selective. The scientific literature contains many examples of voltammetric analyses of controlled drugs. A square wave voltammetric analysis of the novel psychoactive substance benzyl-piperazine is reported here, representing the first time this analysis has been established. A limit of detection of 6 μM was achieved, and resolution against the similar ecstasy-type drug 3-4-methylenedioxymethylamphetamine (MDMA) was demonstrated. Two innovative USB powered prototype potentiostats have been developed. As proof of concept, an ATMega328P microcontroller was used in conjunction with 12-bit digital-to-analog and analog-to-digital converters (MAX532 and MCP3304 respectively). Using ferricyanide for redox at a glassy carbon electrode, reversible cyclic voltammetric analyses and square wave linear calibration (2.7 to 13.7 μM, R2=0.998) were achieved by the first prototype. The second prototype extended the compliance range (from ±2.5 V to ±12 V) and improved the signal to noise ratio. The second prototype also achieved a linear calibration using square wave voltammetry of MDMA (41 to 82 μM, R2=0.995) at a carbon paste electrode