Amperometric immunosensors and enzyme electrodes for environmental applications

Amperometric biosensors can offer a viable, low cost solution to field monitoring in environmental analysis. The rational choice of immobilisation, transduction and biorecognition chemistries is demonstrated in this work to yield improved catalytic and affinity electrochemical biosensors for environmental applications. Thus, graphite electrodes with tyrosinase immobilised in a hydrogel are shown to correlate satisfactorily with the official method for the determination of the phenol index in environmental samples with analysis time of about 2 min per sample. Secondly, a phosphorylase A-phosphoglucomutaseglucose 6-phosphate dehydrogenase biosensor is demonstrated, that, based on the use of this three-enzyme cascade and combined with new beta-nicotinamide adenine dinucleotide (NADH) oxidation mediators, makes it possible to detect phosphate without the addition of any reagent. Thirdly, an immunosensor for atrazine is presented that based on electrochemically 'wired' peroxidase-labelled atrazine and its competition for the binding sites of immobilised antibodies, reached mu g l(-1) detection limits and short incubation times. (C) 1998 Elsevier Science B.V.