Rapid and sensitive detection of pyrimethanil residues on pome fruits by Surface Enhanced Raman Scattering

•A rapid and sensitive method to detect pyrimethanil on apples is presented.•Raman signals of the pesticide are enhanced by drop casting AuNPs on the fruit peel.•120 nm gold nanoparticles provide the best SERS response for this application.•Raman mapping strategy allows to overcome inhomogeneity problems.•Quantitative calibration using Partial Least Squares provides good method stability.

Surface Enhanced Raman Scattering (SERS) supported by gold nanoparticles (AuNPs) was applied to detect and quantify residues of pyrimethanil on pome fruits, a widely used fungicide in horticultural species. Spheroidal AuNPs with different size were fabricated and compared in this study. The analytical procedure was set up on a silicon dioxide flat substrate to standardize SERS methodology. A Raman mapping strategy was exploited to increase signal reproducibility and to minimize bias due to different local surface morphologies. Univariate and multivariate regressions were compared for calibration. Multivariate PLS approach demonstrated acceptable repeatability and method stability (RMSECV = 4.79 ppm; RMSEP = 4.31 ppm) in the range 0-40 mg kg−1, providing higher accuracy and intra-day repeatability with a mean percentage error of 18.7% and 32.8% for PLS and univariate calibration, respectively. The method here proposed can be reliably applied for PMT detection on pome fruits within the European law limits.