No abstract

This paper reports a lab-on-a-chip for the detection of Sarin nerve agent based on rapid electrochemical detection. The chemical warfare agent Sarin (C₄H₁₀FO₂P, O-isopropyl methylphosphonofluoridate) is a highly toxic organophosphate that induces rapid respiratory depression, seizures and death within minutes of inhalation. As purified Sarin is colourless, odourless, water soluble and a easily disseminated nerve agent, it has been used as a weapon in terrorist or military attacks. To ascertain whether potable water supplies have been adulterated with this extremely potent poison, an inexpensive, sensitive and easy to use portable test kit would be of interest to first responders investigating such attacks. We report here an amperometric-based approach for detecting trace amounts of Sarin in water samples using a screen-printed electrode (SPE) integrated in a microfluidic chip. Enzymatic inhibition was obtained by exposing the immobilised biosensor in the microfluidic platform to Sarin in water samples. With the aid of cobalt phthalocyanine modified SPE, the device could detect Sarin at part-per-billion levels with concentration as low as 1 nM. The detection method reported here represents a significant improvement over the authors'previous optical-based detection method.

Acetylcholine (ACh) is a neurotransmitter that is responsible for many of our bodily functions while acetylcholineesterase (AChE) is its enzyme. Certain nerve agents inhibit AChE to cause malfunctions of our body system. To detect those agents, the concentration of AChE by-product, choline, is used as a detection marker. Using a screen printed electrode and acetylthiocholine (ATCh) as a replacement for ACh, amperometry is employed to detect the concentration of the AChE-ATCh reaction by-product, thiocholine. Results showed that 0.1 V is the optimum potential for thiocholine detection. Voltages of 0.2 V and 0.3 V also produced similar current magnitudes. From 0.225 mM to 0.9 mM of thiocholine, the amperometry current exhibits a linear relation with concentration. The sensitivity electrode is around 2.53 µA/mM. A flow rate of 100 µL/min is chosen as it is close to the saturation oxidation rate of the electrode and is useful in practical situations. Taking into account the errors met at 0.1 V, the sensitivity of the system is calculated to a minimum of 0.04 mM.