A faster and more accessible method for the analysis of acephate and methamidophos in water samples by LC-MS/MS

Pesticide pollution on environmental matrices has attracted increasing attention worldwide. Pesticide runoff from agricultural crops into surface waters may impact ecosystems and human health through drinking water consumption in pesticide-polluted areas. This study aims to develop and validate a simpler, faster, and more accessible methodology for the analysis of organophosphate pesticides, such as acephate and methamidophos, using HPLC-ESI-MS (QqQ). Acephate and methamidophos are two of the most common and efficient systemic pesticides in the organophosphate family, known for their high effectiveness against insects and pests. Firstly, different extractions were tested: liquid-liquid extraction (LLE), low-temperature partitioning extraction (LTPE) and solid-phase extraction (SPE) with a usual and accessible cartridge, C18. LLE and LTPE showed low sensitivities, probably because acephate and methamidophos are extremely hydrophilic compounds, like many organophosphorus pesticides. Thus, they have low interaction with the extractor solvent, resulting in low extraction rates. SPE with C18 cartridge led to the best extraction of acephate and methamidophos in water matrices and was chosen for the validated process. The selected method ensured acceptable recoveries, within the same range found in the scientific literature (9–49%) and within relative standard deviations below 20%. However, future efforts regarding other types of cartridges are encouraged. The limit of detection (LOD) and limit of quantification (LOQ) of the analytical method were 0.02 and 0.05 μg/L for acephate and methamidophos, values lower than those reported in the scientific literature. The developed method was used to quantify the levels of such organophosphate pesticides in samples from Brazilian surface water and none of the target pesticides were detected in these aquatic matrices.