气相色谱-串联质谱法测定茶叶中10种酸性除草剂的残留量

取茶叶样品5.00g,用水预先用50%(体积分数)盐酸溶液调节其酸度至pH2.0]10.0mL浸泡30min。先后用乙腈超声提取2次(每次用乙腈20.0mL),每次20min,离心,合并两次提取的上清液,先后于30℃水浴中减压蒸发以及在常温下吹氮至溶液近干,加入乙腈-甲苯-乙酸(75+25+1)混合溶液(简称为ATA混合液)5.0mL溶解残渣,此溶液流经CleanertPesticCarb/NH2固相萃取柱净化。收集流出液(主液),用ATA混合液15.0mL淋洗萃取柱,收集流出液并与主液合并,在常温条件下吹氮至近干。加入丙酮870μL溶解残渣。按文献报道的方法进行五氟苄溴(PFBBr)衍生化于60℃水浴中反应1.0h,用正己烷1.0mL提取所生成的衍生物。按所选条件用气相色谱-串联质谱法测定提取液中10种酸性除草剂的残留量。结果表明:10种酸性除草剂化合物的质量浓度在一定范围内与其峰面积之间呈线性关系,检出限(3S/N)在0.0223~1.54μg·kg^-1。以红茶、绿茶和乌龙茶为基质,按标准加入法进行回收试验,回收率在72.2%~109%之间,测定值的相对标准偏差(n=6)在0.10%~5.2%之间。

GC-MS/MS Determination of Residual Amounts of 10 Acidic Herbicides in Tea

Tea sample (5.00 g) was soaked in 10.0 mL of water which was adjusted to pH 2.0 with (? 50% HC1 solution preliminarily] for 30 min, and extracted ultrasonically twice successively with acetonitrile (20.0 mL for each extraction) for 20 min in each extraction. After centrifugation, the supernatants were collected, combined and evaporated to near-dryness at 30℃ in a water-bath under reduced pressure and further to dryness by N2-blowing at normal temperature. 5.0 mL of a mixture of acetonitrile,toluene and acetic acid (75 + 25 + 1, abbreviated as ATA mixture) were added to dissolved the residue, and the solution obtained was purified by passing through the SPE column of Cleanert Pestic Carb/NH2 and the eluate was collected. The SPE column was then eluted with 15.0 mL of the ATA mixture, and the eluate was collected and combined with the first eluate, and the solution was evaporated to near-dryness by N2-blowing under normal temperature. The residue was dissolved in 870 μL of acetone and the 10 acidic herbicides in the solution were derivatized by the PFBBr method in a water-bath at 60℃ for 1.0 h as described in an optimized procedure given in literature. The derivates formed were then extracted from the reaction mixture with 1.0 mL of n-hexane and in which the derivates were determined by GC-MS/MS method representing residual amounts of the 10 acidic herbicides in the tea sample. As shown by the results, linear relationships between values of peak area and mass concentration of the 10 acidic herbicides were found in the definite ranges, with detection limits (3S/N) in the range of 0.022 3- 1.54μg·kg^-1. Test for recovery by standard addition method was made on the base of black tea, green tea and oolong tea? giving results in the range of 72.2%-109%, and RSDs (n= 6) ranged from 0.10% to 5.2%.