粮谷中灭草松残留量检测的GC及GC-MS／MS研究

STUDY OF THE ANALYSIS OF RESIDUAL BENTAZON IN GRAINS BY GC AND GC-MS/MS

试验证明GC-ECD及GC-MS／MS两种方法均能用于粮谷中残留除草剂灭草松的测定。GC-MS／MS法可同时进行定性和定量分析,测定结果的可靠性较高。GC-ECD法具有较高的灵敏度,用于定量分析的效果较好。提出一种可与上述两种方法接用的试样预处理方法。10 g试样用甲醇提取其中的测定组分,再用正己烷萃取除去脂肪。用稀盐酸调节水相的酸度至pH≤3, 用二氯甲烷将灭草松萃取至有机相。在45℃减压干燥除去溶剂,所得浓缩的残渣溶于0．2 mL甲醇中并进行甲烷化和纯化(用固相萃取法),所得残留灭草松溶于1 mL正己烷中供GC-ECD或 GC-MS／MS测定。用两种方法进行粮谷试样的分析,测定结果的RSD值依次为2．3％-4．7％和 3．5％-6．7％。用标准加入法测得两方法的回收率依次为77％-98％和80％-102％,方法的检出限为0．01 mg·kg-1。

It was proved that either of the method of GC-ECD or of C-C-MS/MS was suitable to be used in the determination of residual bentazon in grains. The method of GC-MS/MS gave qualitative and quantitative results simultaneously, and showed better reliability. The method of GC-ECD showed higher sensitivity, and was more effective in quantitative analysis. A common procedure of sample pre-treatment for both of the above methods was proposed. 10 g of sample was extracted with methanol, and defatted by extraction with n-hexane. The aqueous phase was acidified to pH≤3 with dil. HCl, and the bentazon was then extracted into dichloromethane, which was evaporated to dryness at 45℃ under reduced pressure. The concentrated residue containing the bentazon was dissolved in 0. 2 mL CH3OH, methylated and purified by solid phase extraction. The residual bentazon was dissolved in 1 mL of n-hexane, and was ready for use in CC or GC-MS determination. In the analysis of several grain samples by the above mentioned methods, values of RSD in the range of 2. 3%～4.7% were obtained for GC-ECD, and of 3. 5%～6. 7% for GC-MS/MS. Recoveries obtained by standard addition method were in the ranges of 77%～98% and 80% ～102% for GC-ECD and GC-MS/MS respectively. The limit of determination was found to be 0. 01 mg·kg^-1.