Surface-enhanced Raman spectroscopy-based quantitative detection of agrochemical residues on apple peels utilizing market-available formulations

This study explores a rapid method for detecting commercial pesticide mixtures containing adjuvants on a fruit’s surface. The approach integrates adhesive tape sampling with surface-enhanced Raman spectroscopy (SERS) to simultaneously analyse chlorpyrifos and cypermethrin from industrial pesticide cocktails. The optimal adhesive tape was selected from three commercially available options based on achieving the highest signal-to-noise ratio and the lowest background interference. Residues were extracted using the paste-and-peel method, followed by the application of gold nanoparticles to the tape, thereby converting the tape into a SERS-active substrate for Raman analysis. The method achieved limits of detection (LODs) of 0.33 ppm 0.36 µg/cm2 for chlorpyrifos and 0.5 ppm 0.55 µg/cm2 for cypermethrin, with limits of quantification (LOQs) of 1.1 and 1.65 ppm, respectively, on apple peels. Enhancement factors reached 1.1 × 106 for chlorpyrifos and 2.57 × 105 for cypermethrin, with ∼13% signal variability at the highest concentration. This approach demonstrates effective, repeatable SERS-based detection of pesticide residues in industrial mixtures containing mixed constituents and stabilising adjuvants, rather than analytical standards, thereby supporting field applicability. It provides direct testing of produce surfaces without complex laboratory procedures, delivering results in under 5 minutes. Its high sensitivity and versatility for both thick- and thin-skinned produce make it a powerful tool for food inspectors to safeguard consumer safety.