Determination of Dichlorvos in Pears by Surface-Enhanced Raman Scattering (SERS) with Catalysis by Platinum Coated Gold Nanoparticles

A surface-enhanced Raman scattering (SERS) sensor is reported for the determination of dichlorvos, an organophosphate pesticide (OP), in pears. Platinum coated gold nanoparticles (Au@PtNPs) were used as secondary catalysts to provide signal amplification. Acetylcholinesterase (AChE) catalyzed the hydrolysis of acetylthiocholine to form thiocholine. Thiocholine causes the accumulation of Au@PtNPs, which changes the particle size and prevents their peroxidase-mimicking activity. Dynamic light scattering was used to characterize the particle size. Following the addition of dichlorvos, the AChE activity was inhibited, the production of thiocholine and aggregation were reduced, and the peroxidase mimicing property was retained. In the presence of 3,3′,5,5′-tetramethylbenzidine (TMB), a blue product was produced that provided strong SERS signals. The SERS method showed a linear relationship for dichlorvos concentrations from 20 to 2000 µg/L. The developed protocol had a limit of detection of 20 µg/L. This SERS sensor assay was successfully applied for the quantification of dichlorvos in pears with satisfactory recoveries from 80.25 to 94.86%.