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. T wo different kinds of bienzymatic bioelectrodes are presented: a class ical bienzymatic electrode, obtained by physicochemical immobilization of purified acid phosphatase (AP) and glucose oxidase (GOD) on the ti p 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 tu berosum) tissue, endowed with a high content of enzyme activity. Both the biosensors can selectively detect glucose-6-phosphate (G6P), in th e 5.0x10(-5)-1.2x10(-3) M concentration range. Pesticides are detected , thanks to their high inhibition power towards AP, evaluated by addin g the sample stepwise to a buffered solution of G6P, and recording the corresponding current change. The detection limit is therefore a func tion of the type of pesticide, but it can be as low as 1 mu g l(-1) in the case of organophosphorus compounds. The detection limit is genera lly higher for carbamates, as a consequence of their weaker inhibition power towards acid phosphatase. Both bioelectrodes presented comparab le values of the main physicochemical and analytical parameters evalua ted for assessing their overall performance; nonetheless the plant tis sue based bioelectrode exhibited a longer shelf life and a better reli ability of the amperometric results.