Application of silver nanoparticles for a highly selective colorimetric assay of endrin in water and food samples based on stereoselective endo-recognition

We report a novel and facile strategy for a highly stereoselective colorimetric assay for the detection of endrin pesticide in water and food samples using sucrose capped silver nanoparticles (AgNPs). To the best of our knowledge, to date there is no report of stereoselective single component determination of endrin in water and food samples. The present methodology is based on the measurement of a shift and the appearance of a new localized surface plasmon resonance (LSPR) absorption band of AgNPs in the UV-Vis region, induced by the aggregation of NPs. The aggregation of NPs is due to the stereo-selective endo-recognition of endrin through the high charge electron density of oxygen atoms to silver via non-bonded interactions (O center dot center dot center dot Ag). A control experiment with an isomeric molecule (dieldrin) containing an oxygen at the exo-position did not exhibit any color change under identical experiential conditions. The colorimetric assay for the detection of endrin was optimized, and the best experimental conditions were obtained when the pH of the solution was 7.0 with the addition of a 7 : 3 volume ratio of water and acetone. The linearity range and limit of detection for the determination of endrin were found to be in the range of 0.05-5.00 mu g mL(-1) and 0.015 mu g mL(-1), respectively. Excellent recovery was observed, from 90.0 to 97.0%, and interference studies showed that this method is selective for the determination of endrin in the presence of complex sample matrices.