Residues and decline dynamics of chloroisobromine cyanuric acid in tobacco and soil

The analytical method of fungicide chloroisobromine cyanuric acid and its residues and decline dynamics in tobacco and soil were investigated.Tobacco-leaf or soil samples were extracted with acetonitrile.The extracts were partitioned with trichloromethane and petroleum ether followed by determination with high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) detector.The average recovery at spiked levels of 0.01-0.5 mg/kg ranged from 82.7%-91.6% for fresh tobacco leaf,89.2% -91.8% for dried tobacco leaf and 89.2%-94.4% for soil,with relative standard deviations (RSD) of 1.1% -3.9%,2.6% -5.5% and 1.5% -4.6%,respectively.The limit of detection (LOD) and limit of quantification (LOQ) were determined as 0.003 and 0.01 mg/kg,respectively,for both tobacco and soil samples.Results of the decline dynamics study showed that half-life values (T1/2) were 3.94-4.25 d in fresh tobacco leaves and 2.83-3.41 d in soil,respectively.The ultimate residues of chloroisobromine cyanuric acid in dried tobacco leaves and soil were determined after the third and fourth application at levels of 600 g a.i./hm2 and 900 g a.i./hm2,with the residues ranging from 1.47-3.52 mg/kg in tobacco and below 0.43 mg/kg in soil 21 days after the last treatment.