Selective inhibition-based biosensing system for the determination of pesticides in environmental samples using analytical pervaporation coupled withenzymatic derivatisation

A novel and selective method based on inhibition reactions coupled with a p rior separation step consisting of analytical pervaporation has been design ed and used in order to develop a method for the determination of diclorvos . The method is based on the inhibitory effect of this organophosphorous pe sticide (low boiling point 35 degrees C) on the acetylcholinesterase cataly sis after selective pervaporation of the analyte, The derivatisation reacti on is a two-step reaction involving choline oxidase (ChOD) and horseradish peroxidase (POD) with fluorimetric detection at lambda(ex) = 310 nm and lam bda(em) = 415 nm of the dimer formed, The method applied to liquid samples has a linear determination range of 0.05-0.5 mmol l(-1) (n = 8, r(2) = 0.99 59) with excellent precision (RSD<3.2%) and a sampling frequency of 3 h(-1) . When applied to solid samples the method has a linear determination range of 0.001-0.04 g kg(-1) (n = 5, r(2) = 0.9909, RSD<4.2%) and a sampling fre quency of 2 h(-1). The approach has been applied to the determination of di clorvos in natural water and spiked soil samples with recoveries between 89 .9 and 109.7%. (C) 2000 Elsevier Science B.V. All rights reserved.