Acid phosphatase/glucose oxidase-based biosensors for the determination of pesticides

This work presents new amperometric bienzymatic bioelectrodes for the determination of organophosphorus and carbamic acid type pesticides. Two different kinds of bienzymatic bioelectrodes are presented: a classical bienzymatic electrode, obtained by physicochemical immobilization of purified acid phosphatase (AP) and glucose oxidase (GOD) on the tip of an amperometric H2O2 electrode; and a hybrid biosensor, in which AP has been employed in the form of a thin layer of potato (Solanum tuberosum) tissue, endowed with a high content of enzyme activity. Both the biosensors can selectively detect glucose-6-phosphate (G6P), in the 5.0 × 10−5 −1.2 × 10−3M concentration range. Pesticides are detected, thanks to their high inhibition power towards AP, evaluated by adding the sample stepwise to a buffered solution of G6P, and recording the corresponding current change. The detection limit is therefore a function of the type of pesticide, but it can be as low as 1 μg 1−1 in the case of organophosphorus compounds. The detection limit is generally higher for carbamates, as a consequence of their weaker inhibition power towards acid phosphatase. Both bioelectrodes presented comparable values of the main physicochemical and analytical parameters evaluated for assessing their overall performance; nonetheless the plant tissue based bioelectrode exhibited a longer shelf life and a better reliability of the amperometric results.