Development and validation of a gas chromatography method for quantifying metham sodium in diverse plant origin foods

To ensure food safety and public health, it is essential to establish dependable methods for the qualitative and quantitative analysis of pesticide residues in plant origin foods. This study developed and optimized a gas chromatographic method using the QuEChERS approach for detecting metham sodium residues in 22 plant origin foods. The method was refined by adjusting inlet temperature and transformation conditions to effectively convert metham sodium into its primary metabolite, methyl isothiocyanate. Furthermore, parameters such as the extraction solvent type, volume, and purifying agent were systematically optimized. The method achieved a limit of quantification (LOQ) of 0.05 mg/kg, with a linear range from 0.025 to 1.0 mg/L and determination coefficients (R²) from 0.9892 to 0.9999. Recovery rates ranged from 82 % to 102 %, with relative standard deviations (RSDs) between 0.3 % and 6.8 %. Inter-laboratory validation, in accordance with EU SANTE guidelines, confirmed the method's accuracy and reliability. Validation results passed Cochrane's and Grubbs' tests, with repeatability RSDs between 0.70 % and 5.28 % and reproducibility RSDs from 3.62 % to 21.89 %. This method provides a reliable and effective approach for determining metham sodium residues, and addresses a critical gap in current analytical techniques, offering significant contributions to residue monitoring and food safety regulations.