Determination of oxyfluorfen, carfentrazone-ethyl and etoxazole residues in four spices using gas chromatography-tandem mass spectrometry

An analytical method was developed for the determination of oxyfluorfen, carfentrazone-ethyl and etoxazole in Mentha spicata L, Cinnamomum cassia Presl, Mentha piperita L, and Laurus nobilis L using gas chromatography-tandem mass spectrometry (GC-MS/MS). The spice matrices were hydrated by ultrapure water, extracted by acetonitrile followed by the salting out process with anhydrous magnesium sulfate and sodium chloride then purified using the NH₂-Carb column and determined by the GC-MS/MS under MRM mode. The calibration curve showed a good linearity in the range of 0.0025-2 mg/L (oxyfluorfen) and 0.01-2 mg/L (carfentrazone-ethyl and etoxazole), with the correlation efficient above 0.99. The average recoveries of oxyfluorfen in the four kinds of matrices at three spiked levels of 0.025, 0.5 and 2 mg/kg ranged from 86% to 112%, with the relative standard deviation (RSD) between 2.4%-9.6%. The average recoveries of carfentrazone-ethyl at three spiked levels of 0.2, 0.5 and 2 mg/kg ranged from 87% to 114%, with the RSD between 2.4%-11%. The average recoveries of etoxazole at three spiked levels of 0.5, 2 and 5 mg/kg ranged from 86% to 116%, with the RSD between 3.2%-11%. The limit of quantitation (LOQ) of oxyfluorfen, carfentrazone-ethyl and etoxazole in the four spices were 0.025, 0.2 and 0.5 mg/kg, respectively.