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An ampezometnc blosensor for the detection of organophosphate and carbamate pesticides was constructed as a disposable stnp contaming a cobalt phthalocyanme-modlfed carbon composite electrode and a cross-lmked chohnesterase layer With butyrylthmchohne as substrate, enzymatlcally produced thmchohne was oxldned at + 250 mV The steady-state current, I,, was used as a measure of the enzyme actlvlty In the presence. of pestlades, an u-reversible mhlbltlon of chohnesterase occurred, resulting m a decrease m the rate of current change, dI/dr
The ratio (dl/dr)/Z,, was used for evaluations The Influence of the chohnesterase loading and the cholmesterase to glutaraldehyde ratio on the blosensor response was studled and the measuring condltlons (pH, temperature, substrate concentration) were optmnzed Detection hmlts of 0 30, 12 and 11 nmol 1-l for paraoxon, dlchlorvos and carbaryl, respectively, were achieved The time of mhlbltlon varied from a few seconds (high pestlclde concentrations) to 6 mm reqmred for rehable measurements at levels close to the detection hmlt When the analysis was performed by 10 mm premcubatlon of the bmsensor or free chohnesterase mth sample, paraoxon concentrations above 3 0 nmol I-' could be detected