RESUMO
A method for the determination of seven kinds of thiocarbamate herbicides, molinate, pebulate, vernolate, triallate, thibencarb, eradicane and butylate in black tea and green tea has been developed. After homogenization, 2.0 g tea sample was soaked with 6 mL water for 1 h. 2.5 g NaCl was then added, and the sample was extracted twice by 20 mL acetonitrile. After concentration, the extract was put through HLB column and eluted by 3 mL acetonitrile. The eluate was then concentrated and dissolved with 2.0 mL hexane-acetone (7∶ 3, V/V) mixture. The preparation was cleaned by Envi-Carb column and eluted with 5 mL hexane-acetone. After concentration, the residue was dissolved by acetonitrile-water (5∶ 5, V/V) solution. Detection was achieved by electrospray ionization(ESI) in positive mode using multiple reaction monitoring. D_3-carbaryl was used as the internal standard, the linear range for the herbicides was 0-200 μg/L and the limit of detection were from 0.093 to 1.77 μg/L, with the correlation coefficients(r) varying from 0.9954 to 0.9988. The recoveries of all thiocarbamate herbicides were from 77.3% to 91.5% at the spiked levels of 5-20 μg/kg. The RSD of each compound was less than 15%. Black tea and green tea samples were successfully analyzed by the proposed method with satisfactory results.