Establishment of rapid detection method of methamidophos in vegetables by surface enhanced Raman spectroscopy

Methamidophos (MAP) is a highly efficient and broad-spectrum organophosphate pesticide. In this study, a rapid method for detecting MAP in vegetables using surface enhanced Raman scattering (SERS) spectroscopy has been established. Density functional theory calculations were performed with Gaussian 03 at RB3LYP level and with the 6-311G (d) basis set. SERS, normal and theoretical Raman spectroscopy were compared to investigate the mechanism of Raman scattering enhancement. The SERS signal of MAP was improved in alkaline conditions with optimum scattering efficiency at pH of 13.46. Furthermore, MAP detection in vegetables by SERS method had a good linear relationship between 0.01 and 1,000 μg/mL. The concentration of MAP in vegetables was detected and chosen for recovery test with three levels: 4, 8, and 15 μg/mL. The results of three level tests were 86.7–96.6 % and their relative standard deviations were between 1.2 and 2.5 %, which shows the good repeatability of this method.