Rapid Prescreening of Trace Imidacloprid in Drinking Water via Concentration-Dependent Surface-Enhanced Raman Spectroscopic Patterns

Imidacloprid, the most extensively utilized neonicotinoid insecticide in crop fields, is increasingly being detected in drinking water sources, thereby posing significant risks to human health. Unfortunately, conventional methods for imidacloprid analysis in drinking water, such as liquid chromatography-tandem mass spectrometry (LC-MS/MS), are prohibitively expensive and time-consuming, rendering them unsuitable for large-scale monitoring. The study described herein explores a surface-enhanced Raman spectroscopic (SERS) method as a prescreening tool for imidacloprid detection and quantification in drinking water supplies. It was observed that the SERS patterns of imidacloprid on gold nanoparticle (AuNP) surfaces exhibited variations corresponding to its decreasing concentration, which was harnessed for imidacloprid quantification without reliance on internal standards. Furthermore, the study identified and mitigated the primary interferences encountered in drinking water sourced from groundwater and surface water through a process known as "background" subtraction. This approach yielded an exceptional 100% reliability in detecting imidacloprid at a concentration of 0.01 mu M in 30 independently collected samples, with up to ten measurements conducted for each sample. By employing a customized data processing pipeline comprising techniques such as principal component analysis, SERS barcoding, and vector angle calculation, the limit of detection was further refined to 0.001 mu M. This innovative analytical method, characterized by its rapidity, affordability, and lack of internal standards, represents the first successful application relying solely on SERS patterns for chemical quantification. It holds immense potential for enabling high-throughput prescreening of imidacloprid in drinking water supplies.