气相色谱-质谱法测定茶叶中29种酸性除草剂的残留量

建立了茶叶中29种酸性除草剂残留量的气相色谱-质谱测定与确证方法。采用乙腈超声振荡提取试样中29种酸性除草剂,石墨化炭黑固相萃取柱净化,三甲基硅烷化重氮甲烷衍生化,再经弗罗里硅土固相萃取柱净化,用气相色谱-质谱法选择离子监测方式测定,外标法定量,根据离子丰度比确证。在加标水平为0.01,0.05,0.1 mg/kg时,29种目标物的加标回收率为57.1%～120.4%,相对标准偏差(RSD)为4.3%～20.9%;方法的检出限在0.002～0.005 mg/kg之间。该方法准确、灵敏、快速,可满足国际上对茶叶中29种酸性除草剂残留的检测需要。

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×0.25 mm×0.25 μm) with a column temperature gradient from 50 ℃ (held for 1 min) to 160 ℃ at a rate of 4 ℃/min, held for 3 min and then increased to 300 ℃ for 5 min at a rate of 10 ℃/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.