[Determination of 29 acidic herbicide residues in tea by gas chromatography-mass spectrometry].

A method was developed for the determination of 29 herbicide residues in tea. The target analytes were extracted with acetonitrile. The extract was cleaned up with an ENVI-Carb solid phase extraction column and derivatized with trimethylsilydiazmethan, then cleaned up through a Florisil solid phase extraction column. The derivatives were determined by gas chromatography-mass spectrometry (GC-MS) with selected ion monitoring (SIM) mode. The separation and quantification were achieved using an HP-5MS silica capillary column (30 m x 0.25 mm x 0.25 microm) with a column temperature gradient from 50 degrees C (held for 1 min) to 160 degrees C at a rate of 4 degrees C/min, held for 3 min and then increased to 300 degrees C for 5 min at a rate of 10 degrees C/min. The average recoveries of these herbicides at three spiked levels (0.01, 0.05 and 0.1 mg/kg) ranged from 57.1% to 120.4% with the relative standard deviations (RSDs) ranged from 4.3% to 20.9%. The detection limits were from 0.002 mg/kg to 0.005 mg/kg. The method is easy, fast, and more sensitive. It also indicated that this method can meet the requirements for simultaneous determination of 29 herbicides in tea.