Selective inhibition-based biosensing system for the determination of pesticides in environmental samples using analytical pervaporation coupled with enzymatic derivatisation Original Research Article

A novel and selective method based on inhibition reactions coupled with a prior separation step consisting of analytical pervaporation has been designed and used in order to develop a method for the determination of diclorvos. The method is based on the inhibitory effect of this organophosphorous pesticide (low boiling point 35°C) on the acetylcholinesterase catalysis after selective pervaporation of the analyte. The derivatisation reaction is a two-step reaction involving choline oxidase (ChOD) and horseradish peroxidase (POD) with fluorimetric detection at λex=310 nm and λem=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, r2=0.9959) 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, r2=0.9909, RSD<4.2%) and a sampling frequency of 2 h−1. The approach has been applied to the determination of diclorvos in natural water and spiked soil samples with recoveries between 89.9 and 109.7%.