Rapid simultaneous detection of multi-pesticide residues on apple using SERS technique.

A rapid and straightforward method has been employed to simultaneously detect two pesticides (thiram and methamidophos (MTD)) on apple surface using surface enhanced Raman scattering (SERS) technique. In the experiment, ethanol was dropped onto the contaminated apple surface for pesticide extraction and then gold@silver core-shell nanorods (Au@Ag NRs) were added to generate the SERS signals of the pesticides. Under a laser excitation at 632.8 nm, prominent SERS peaks of blended contaminants were observed, which were chosen to characterize and quantify their concentration. It was found that the SERS intensity of these two peaks changed as a function of the concentration ratio of thiram to MTD. In addition, a better SERS enhancement performance of Au@Ag NRs was demonstrated compared with that of gold nanorods. Our experimental results show that the lowest detectable concentration on apple surfaces is ∼4.6 × 10(-7) M for thiram and ∼4.4 × 10(-4) M for MTD. This study provides a straightforward method for the simultaneous detection of multiple pesticides on fruit surfaces, which is important for food safety and human health.