Sonochemically fabricated acetylcholinesterase micro-electrode arrays within a flow injection analyser for the determination of organophosphate pesticides

This report describes the development of novel sonochemically fabricated, bioengineered acetylcholinesterase and polyaniline carbon/cobalt phthalocyanine biosensors for the ultra-sensitive determination of a number of different pesticides. Arrays of this type typically have population micro-electrode densities of up to ∼2 × 105 cm−2; these represent the highest micro-electrode population densities reported to date by any fabrication means. The enzymatic response of the sensors is inhibited upon incubation with the pesticide, and we have shown that Dichlorvos, Parathion and Azinphos may be determined down to concentrations of ∼1 × 10−17 M, ∼1 × 10−16 M and ∼1 × 10−16 M, respectively. These lower limits of detection are lower than otherwise achievable by any other analytical approach. Measurements were performed within a custom built flow injection system that operates at a constant flow of 1 ml min−1. Sensor stability studies were also performed whereby a stabiliser mixture of sucrose and polygalacturonic acid was added to the immobilised enzyme matrix at the working electrode and left to dry. Sixty-five percent of the initial enzyme activity was found to remain after a period of 92 days to allow storage of these electrodes and facilitating transportation if required.