VALIDATION OF AN ENZYMATIC BIOSENSOR WITH LIQUID-CHROMATOGRAPHY FOR PESTICIDE MONITORING

This article summarizes the need for validation of the use of biosenso rs as field measurement techniques in environmental monitoring. An enz ymatic biosensor based on the reaction of acetylthiocholine chloride, which is enzymatically hydrolyzed to thiocholine and gives a disulfide compound by dimerization, was validated using liquid chromatographic techniques for the determination of various organophosphorus pesticide s and carbaryl in water at levels varying from 0.1 to 5.7 mu g/l of in dividual compounds. With both techniques the batch of water containing the greater amount of pesticides also gave the higher signal via the biosensor. The total number obtained with the biosensor could be used as a positive indication of the presence of the target pesticides and could distinguish the presence of 3.9 and 10.3 mu g/l of total target pesticides in the water sample. In a second step, an on-line oxidation of the samples took place and the different oxo metabolites of the pe sticides were determined by both biosensor and liquid chromatographic detection. The use of diode-array detection permitted unequivocal conf irmation of the various oxo metabolites from their UV spectra