PRINTED AMPEROMETRIC SENSOR BASED ON TCNQ AND CHOLINESTERASE

A relatively simple printed sensor, based on 7,7,8,8-tetracyano quinodimethane-modified graphite and immobilised butyrylcholinesterase [EC.3.1.1.8] was described. The amperometric sensor operated at a potential of 100 mV versus Ag/AgCl (printed) and was sensitive to inhibition by organophosphates. At neutral pH, using S-butyrylthiocholine as the substrate, the kinetic constants, K(m(app)) and I(max), were 2.5 mM and 33-mu-A respectively. The sensor displayed maximum sensitivity at pH 8.0 and a temperature optimum of 40-degrees-C. In the temperature range 3-33-degrees-C, the activation energy of the sensor was 11.8 kcal mol-1 with a temperature coefficient of 6.7% at 25-degrees-C. The sensor was inactivated by phenylmethylsulphonyfluoride and diisopropylfluorophosphate. The range of sensitivity to organophosphates was between 0.06 and 8 ppm.