Development of a portable SERS tool to evaluate the effectiveness of washing methods to remove pesticide residue from fruit surface.

Background: Pesticides are widely used in agriculture to control pests and enhance crop yields. However, post-harvest, there are growing concerns about the potential health risks posed by pesticide residues on produce surfaces. Analyzing these residues is challenging due to their typically low concentrations and the potential interference from the complex matrix of the produce's surface. The problem addressed in this study is the need for a sensitive, rapid, and on-site capable method to detect and quantify pesticide residues on agricultural products.

Results: We developed a portable surface-enhanced Raman spectrometer (SERS)-based approach that offers a rapid 10-min turnaround, simplified protocol, on-site capability, and high sensitivity. Using the new analytical method, we evaluated pesticide residues on fruit surfaces after household or industrial postharvest washing, specifically the efficacy in removing the fungicide ferbam from peach surfaces. The limit of detection (LOD) for our method was determined to be 0.012 mg/kg, significantly lower than the U.S. Environmental Protection Agency's regulated limit of 7 mg/kg for ferbam on peaches. Our data shows that soaking in tap water for 1 min is the least effective method for removing ferbam, with insignificant difference from the control group. In contrast, soaking in a vinegar-water or NaHCO-water solution for 5 min, as well as in a sodium hypochlorite solution (12 % available chlorine) for 1 or 5 min, proved to be the most effective methods. Extended soaking improved pesticide removal for tap water, vinegar, and NaHCO, while in the chlorine groups, the effect was insignificant. SERS analysis revealed negligible penetration of ferbam into peach flesh and the inner surface of the skin.

Significance: This study introduces an innovative method for measuring pesticide residues, significantly enhancing our understanding of pesticide removal and penetration. This new analytical approach is crucial for effectively detecting pesticides and mitigating their exposure through food sources.