Study on residues and dissipation of tebuconazole in grapes and soil

A gas chromatography method was developed for determining tebuconazole residues in grapes and soil.The samples were extracted with acetonitrile or methanol,cleaned up by methylene dichloride and determined by gas chromatograph with Nitrogen Phosphorus Detector(GC-NPD).Results showed that at fortified levels of 0.01 to 1 mg/kg,the ranges of average recoveries and relative standard deviations of the method were 85.0% to 98.8%,2.9% to 10.4% respectively.The limit of detection was estimated to be 1×10-11 g,and the limit of quantification was 0.01 mg/kg.Sprayed with high dosage of 187.5 mg(a.i)/L,the half-life of tebuconazole was 9.8 to 12.2 days in grapes and 8.2 to 17.3 days in soil.Terminal residues in grapes were less 0.81 mg/kg after 28 and 35 days,below the MRL of CAC and China(2.0 mg/kg).Recommended dosage of 187.5 mg(a.i)/L for tebuconazole 250 g/L EW was suggested to apply in grapes with preharvest interval at 28 days and maximum application below three times.