Dissipation and residue determination of fluopyram and tebuconazole residues in watermelon and soil by GC-MS

Abstract

A sensitive and selective method has been developed for the simultaneous determination of fluopyram and tebuconazole in watermelon and soil. The method involves an extraction procedure with acetonitrile using high-speed blender, a cleanup procedure by dispersive solid phase extraction (d-SPE) and determination using gas chromatography-mass spectrometry (GC-MS). The method has been validated for watermelon and soil samples spiked at 0.01, 0.1 and 0.5 mg/kg. The average recoveries of fluopyram and tebuconazole were found in the range of 88.2–106% with relative standard deviations (RSDs) of 1.52–7.65%. A limit of quantification (LOQ) of 0.01 mg/kg was obtained for both compounds. The residual levels and dissipation rates of fluopyram and tebuconazole in real watermelon and soil were determined. The half-lives of fluopyram were 6.48–6.60 days in watermelon and 15.8–24.8 days in soil. The half-lives of tebuconazole were 5.87–6.93 days in watermelon and 11.2–14.4 days in soil. The terminal residues of fluopyram and tebuconazole were all below the maximum residue limits (MRLs) value set by USA (fluopyram, 1 mg/kg; tebuconazole, 0.09 mg/kg). Hence it was safe for the use of the two pesticides and the results also could give a reference for MRLs setting of fluopyram and tebuconazole in watermelon in China.