Optimization of the methodology for the extraction of organophosphate pesticides by HS–SPME–GC–NPD

OptOrganophosphate compounds are widely present in the environment and are known to exert harmful effects on human health by inhibiting acetylcholinesterase (AChE), a key enzyme of the nervous system. This study aimed to optimize a solvent-free extraction methodology to determine five organophosphate residues —chlorpyrifos, methamidophos, fenitrothion, dichlorvos, anddimethoate— in water samples using solid-phase microextraction (SPME) combined with gas chromatography and nitrogen–phosphorus detection (GC–NPD). We applied an experimental design to evaluate five critical variables: fiber type, extraction time, temperature, stirring speed, and salt concentration. The best extraction performance was achieved by using a DVB/CAR/PDMS fiber for 20 minutes at 50°C, 500 rpm, and 1% NaCl. Under these conditions, the method had excellent linearity (r2 up to 0.9892), detection limits between 1.088 and 3.114 μg/L, quantification limits between 3.264 and 9.342 μg/L, and precision with %RSD values ranging from 0.998 to 3.599. These results confirmed that the proposed method is fast, simple, sensitive, and robust. Its optimization contributes to the development of green analytical strategies for monitoring pesticide contamination in aqueous environments.