气相色谱法测定地下水中拟除虫菊酯有机氯百菌清等24种农药残留

摘要

High sensitivity is required to determine pyrethroids,organochlorines,chlorothalonil and chlorpyrifos by using Gas Chromatography-Micro-Electron Capture Detector( GC-μECD)due to their high electro-negativity. The sensitivity of pyrethroids,which have higher molecular weights,is much lower than organochlorines. Moreover,the efficiency of determination is very low by different analyses patterns. This problem has been solved by using a column pressure program,and 24 compounds were determined efficiently at the same time by optimizing column conditions and inlet temperature. The underground water sample was treated by liquid-liquid extraction,Florisil SPE cleanup and analyzed by RTX-CL Pesticides 2 with GC-μECD. The calibration curves for 24 compounds were linear in the range of 0. 5-6000 ng/mL,and the method detection limits were in the range of 1. 00-12. 00 ng/L. The matrix spiked experiments were studied at three different concentration levels. The mean recoveries for low,middle and high concentration were in the range of 80. 3% -116%,79. 9% -117% and 85. 7% -102% with precisions of 1. 5% -6. 8%,1. 3% -7. 6% and 1. 1% -6. 8%,respectively. Compared to common chromatographic column(DB-5MS), the special chromatographic column( RTX-CLPesticides 2 ) is more efficient for analyzing multiple targets and category compounds. The low sensitivity and peak tailing problem of pyrethroids caused by long residence time in column was solved by using a column pressure program. The method is sensitive,accurate,and economical and maintains a high flux,which is easy to determine multiple pesticide residues simultaneously.%拟除虫菊酯类、有机氯、百菌清等农药均属于电负性强化合物，采用气相色谱-电子捕获检测器（ GC-ECD）检测具有较高的灵敏度，但由于拟除虫菊酯类农药分子量较大，其灵敏度显著低于有机氯，使得各类化合物进行分类检测的流程长、分析效率低。本文通过优选分析色谱柱和进样口温度等条件，利用气相色谱的色谱柱程序升压功能实现了多类别24种农药残留的快速、准确测定。实验中以正己烷为溶剂进行液液萃取，Florisil固相萃取柱净化，选择有机氯专用色谱柱（ RTX-CLPesticides 2）进行分析，GC-ECD仪器在0.5~6000 ng/mL浓度范围内呈线性，方法检出限为1.00~12.00 ng/L，低、中、高三个浓度水平的加标回收率分别为80.3%~116%、79.9%~117%、85.7%~102%，相应的精密度（RSD，n=7）为1.5%~6.8%、1.3%~7.6%、1.1%~6.8%。本方法选用的有机氯专用色谱柱（ RTX-CLPesticides 2）对多组分、多类别目标化合物有更好的分辨率，较通用型色谱柱（ DB-5 MS ）更具分析优势；采用的色谱柱程序升压技术解决了拟除虫菊酯类化合物在气相色谱柱中停留时间过长而导致的低灵敏度、峰拖尾等技术难题。此方法灵敏、经济，分析通量高，可有效地同时分析多种类农药残留物质。