Rapid detection of pesticide residue in apple based on Raman spectroscopy

The potential of Raman spectroscopy in the analysis of low concentration organic contaminants on apples' surface was evidenced in this study. Chlorpyrifos, an organophosphorus pesticide, was used as a probe for this purpose. The characteristic peaks of fingerprints of pesticide on an aluminum substrate and apple fruit cuticle without pesticide residue were acquired first. Then a concentration range of chlorpyrifos (commercial products at 40%) solutions were made using deionised and distilled water. Single 100 μL droplets of the chlorpyrifos solutions were placed gently on apple fruit cuticles and left to dry before analysis. Through comparative analysis of the Raman spectra data collected, 341, 632 and 1237cm-1 were identified to detect the chlorpyrifos pesticide residue on apple surface. Based on the relationship between the Raman intensity of the most prominent peak at around 632cm-1 and the pesticide concentrations, the limit of detection of ordinary Raman spectrum for chlorpyrifos was estimated to be 48ppm.