Enzyme biosensor for determination of organophosphates

A potentiometric enzyme biosensor for the direct measurement of organophosphate pesticides was developed. The basic element of this enzyme biosensor was a pH electrode modified with an immobilized organophosphorus hydrolase layer formed by cross-linking OPH with bovine serum albumin and glutaraldehyde. Organophosphorus hydrolase catalyzes the hydrolysis of organophosporus pesticides to release protons, the concentration of which is proportional to the amount of hydrolyzed substrate. The organophosphate enzyme biosensor had a response time of less than 3 min, a useful operating range of 0.002–0.4 mM for paraoxon and parathion, and a long-term stability of over a month when stored in pH 8.5, 1 mM HEPES + 100 mM NaCl buffer at 4 °C. The effects of various parameters, buffer concentration, pH, temperature and enzyme loading are described.