Characterisation of a thermophilic L-glutamate dehydrogenase biosensor foramperometric determination of L-glutamate by flow injection analysis

Carbon paste wax electrodes incorporating thermophilic L-glutamate dehydrog enase, NADP and a polymeric toluidine blue O (poly-TBO) mediator have been characterised for the amperometric determination of L-glutamate at 313-318 K in a flow injection analysis (FIA) system. The biosensors exhibit good se nsitivity, mechanical stability and reproducibilty, unlike carbon paste- or carbon wax-based electrodes under the same conditions. The carbon paste wa x electrode responds linearly to L-glutamate up to 40 mM, the detection lim it is 0.3 mM and the RSD (n = 10) for 5 mM L-glutamate was 7.6%. The respon se to some potential interferents has been quantified. Addition of finely g round hexaammineruthenium (III) trichloride ([Ru(NH3)(6)]Cl-3) to the carbo n paste wax electrodes decreases the FIA peak width and increases the peak current. The metal complex appears to accelerate the rate of oxidation of N AD(P)H by poly-TBO. (C) 1999 Elsevier Science S.A. All rights reserved.