A novel, uncomplicated and rapid method of analysis for organophosphorus (OP) pesticides wasresearched and developed using the important, common OP, dipterex, as a typical
example. The basisof the method involved the citrate-capped silver nanoparticles (citrate-capped AgNPs) and Acetylthio-choline (ATCh). The latter compound can be catalyzed by Acetylcholinesterase (AChE) to form thiocholine(TCh), which induces the aggregation of AgNPs. Correspondingly, the color of AgNPs in solution changesfrom bright yellow to pink, and the UV–vis characteristic absorption peak of AgNPs at about 400 nmdecreases; simultaneously, a new absorption band appears at about 520 nm. Irreversible inhibition ofAChE activity caused by dipterex, prevents the aggregation of AgNPs. Thus, a UV–vis spectrophotometricmethod was developed for the analysis of dipterex. The absorbance ratio A396 nm/A520 nmwas found tobe linearly related to the concentration of dipterex in the range of 0.25–37.5 ng mL−1with a detectionlimit of 0.18 ng mL−1. This method was used successfully to analyse dipterex in spiked, different watersamples.