Determining tolfenpyrad in oat samples using solid–liquid extraction with low-temperature purification and analysis by gas chromatography coupled with mass spectrometry

Tolfenpyrad is an insecticide classified as highly toxic to humans, and was recently approved for use in oat cultivation in Brazil. This approval has raised concerns about potential food safety risks in the country. Thus, the present study aims to optimize and validate solid-liquid extraction with low-temperature purification followed by analysis by gas chromatography coupled with mass spectrometry to quantify tolfenpyrad in oats to facilitate monitoring and inspection for tolfenpyrad use in oat samples. The method consisted of adding 4 g of oats, 4 mL of water, and 8 mL of pure acetonitrile to a bottle with a cap. The mixture was shaken, centrifuged, and refrigerated at -20 °C for 1 h. The supernatant obtained was then transferred to a Falcon tube with 500 mg of Na₂SO₄ and 150 mg of C18 sorbent. The mixture was again shaken and centrifuged, and the supernatant was subsequently removed for chromatographic analysis. Under optimized conditions, the method showed selectivity, accuracy, and precision with a recovery of 99.25% and a relative standard deviation of 2.70%. The validated linear range was 3.0 to 150 μg kg^-1, with detection and quantification limits of 0.5 and 3.0 μg kg^-1, respectively. The calculated matrix effect was 89.23%. The optimized and validated technique was applied to 19 real samples and three samples presented tolfenpyrad at concentrations of 11 to 45 μg kg^-1. These results demonstrate the method's potential as a practical tool for routine monitoring of pesticide residues, contributing to strengthening food safety control.