Residue and decline study of kasugamycin in paddy water and paddy soil

A method for the determination of kasugamycin residue in paddy water and soil was established by means of SCX-solid phase extraction(SPE)and high performance liquid chromatography(HPLC).The paddy water sample was filtrated directly and then cleaned up by SCX-SPE column,while the samples in soil were extracted with V(acetone)∶V(water)=3∶7 by ultrasonic wave and cleaned up by SCX-SPE column.The kasugamycin was determinated by ion-pair reversed-phase high performance liquid chromatography(IP-HPLC)with heptane sulfonicacid sodium.The linear ranges were 0.05-5.0 mg/L and 0.01-0.5 mg/kg with the linear correlation coefficient of 0.999 9.The average fortification recovery of paddy water was 83.8%-92.4% with relative standard deviation(RSD)of 3.67%-5.21% and that of paddy soil was 79.7%-84.5% with relative standard deviation(RSD)of 4.39%-5.62% when kasugamycin was spiked at 0.01-0.5 mg/L level.The limits of detection(LOD)for kasugamycin was 0.001 mg/L in paddy water,and 0.001 mg/kg in paddy soil.The limits of quantification(LOQ)for kasugamycin in paddy water and paddy soil were 0.01 mg/L and 0.01 mg/kg.The method was used to detect the degradation of kasugamycin in the paddy water and soil in Guangdong,Guangxi and Hubei in 2011.The degradation research of kasugamycin in paddy water and soil suggested that the decline curves accorded with the first-order kinetics equation.Kasugamycin declined fast in paddy water,the half-life of kasugamycin in paddy water was 2.88 d (Guangdong),2.52 d(Guangxi) and 2.68 d(Hubei),respectively.Kasugamycin declined slower in the paddy soil than in the paddy water.The half-life of kasugamycin in paddy soil was 4.12 d (Guangdong),5.41 d(Guangxi)and 4.89 d(Hubei),respectively,indicated that the Kasugamycin was digested easy in the paddy soil and paddy water.