Li Hong-Ping, Lin Chiu-Hua, Jen Jen-Fon
Residue Control Division, Taiwan Agricultural Chemicals and Toxic Substances Research Institute, Council of Agriculture, Wu-Fong, Taichung County 413, Taiwan.
Talanta. 2009 Jul 15;79(2):466-71. doi: 10.1016/j.talanta.2009.04.013. Epub 2009 Apr 16.
A one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) has been applied to be a pretreatment step in the analysis of aqueous pyrethroid residuals by gas chromatography (GC) with electron capture detection (ECD). Microwave heating was applied to accelerate the vaporization of pyrethroids (bioallenthrin, bifenthrin, fenpropathrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin, fluvalinate, fenvalerate and deltamethrin) into the headspace, and then being absorbed directly on a SPME fiber under the controlled conditions. Optimal conditions for the SPME sampling, such as the selection of sampling fiber, sample pH, sampling temperature and time, microwave irradiation power, desorption temperature and time were investigated and then applied to real sample analysis. Experimental results indicated that the extraction of pyrethroids from a 20-mL aquatic sample (pH 4.0) was achieved with the best efficiency through the use of a 100-microm PDMS fiber, microwave irradiation of 157 W and sampling at 30 degrees C for 10 min. Under optimum conditions, the detections were linear in the range of 0.05-0.5 microg/L with the square of correlation coefficients (R(2)) of >0.9913 for pyrethroids except bifenthrin being 0.9812. Method detection limits (MDL) were found to be varied from 0.2 to 2.6 ng/L for different pyrethroids based on S/N (signal to noise)=3. The coefficients of variation (CVs) for repeatability were 7-21%. A field underground water sample was analyzed with recovery between 88.5% to 115.5%. This method was proven to be a very simple, rapid, and solvent-free process to achieve the sample pretreatment before the analysis of trace pyrethroids in aqueous samples by gas chromatography.
一步微波辅助顶空固相微萃取（MA-HS-SPME）已被用作气相色谱（GC）结合电子捕获检测（ECD）分析水性拟除虫菊酯残留的预处理步骤。采用微波加热加速拟除虫菊酯（生物烯丙菊酯、联苯菊酯、甲氰菊酯、氯氟氰菊酯、氯菊酯、氟氯氰菊酯、氯氰菊酯、氟胺氰菊酯、氰戊菊酯和溴氰菊酯）挥发至顶空，然后在控制条件下直接吸附到固相微萃取纤维上。研究了固相微萃取采样的最佳条件，如采样纤维的选择、样品pH值、采样温度和时间、微波辐射功率、解吸温度和时间，然后将其应用于实际样品分析。实验结果表明，使用100μm聚二甲基硅氧烷（PDMS）纤维、157W微波辐射以及在30℃下采样10min，可从20mL水样（pH4.0）中以最佳效率萃取拟除虫菊酯。在最佳条件下，除联苯菊酯的相关系数平方（R²）为0.9812外，其他拟除虫菊酯的检测线性范围为0.05 - 0.5μg/L，相关系数平方（R²）>0.9913。基于信噪比（S/N）=3，不同拟除虫菊酯的方法检出限（MDL）在0.2至2.6ng/L之间变化。重复性变异系数（CV）为7 - 21%。对一个野外地下水样进行分析，回收率在88.5%至115.5%之间。该方法被证明是一种非常简单、快速且无溶剂的过程，可用于在气相色谱分析水样中痕量拟除虫菊酯之前进行样品预处理。
