Rapid, simple and quantitative detection of metolcarb residues in apples by surface-enhanced Raman scattering

A rapid and simple detection method of metolcarb residues in apples with spectral analysis technology was achieved drawing support from the high sensitive and flexible silver/dragonfly wing (Ag/DW) surface-enhanced Raman scattering (SERS) substrates. The three steps “spray”, “press” and “separate” greatly simplified the procedures of extraction and sampling of pesticide molecules, resulting in the entire detection process was completed just in a few minutes. Importantly, the Ag nanoislands offered strong electromagnetic (EM) field enhancement near metallic nanostructures and significantly improved the sensitivity and reproducibility of the Raman signals. Meanwhile, surface plasmon coupling at the nanogaps between adjacent nanoislands created abundant “hot spots”, which became enormous enhancement necessary for high sensitivity SERS detection of metolcarb. Taking the apple peels as carriers, the trace detection of metolcarb residues on them was realized, whose detection limit reached 1×10-9 g/cm2. In addition, the linear relationship (R2 = 0.98666) between the logarithmic concentrations of metolcarb residues and the logarithmic peak areas at 1581 cm-1 was established, which was the more accurate reference for the prediction of the unknown concentration of metolcarb residues. In order to carry out the actual emulation, we studied metolcarb in mixed solution, and its obvious characteristic peaks were observed. These results indicated that SERS technology coupled with “spray-press-separate-test” method had the potential to qualitatively and quantitatively analyse metolcarb residues on complex apple peels.