Analysis of aqueous pyrethroid residuals by one-step microwave-assisted headspace solid-phase microextraction and gas chromatography with electron capture detection

摘要

A one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) has been appliedto 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 ofpyrethroids (bioallenthrin, bifenthrin,fenpropathrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin,fiuvalinate, fenvalerate and deltamethrin) into the headspace, and then being absorbed directly on a SPMEfiber under the controlled conditions. Optimal conditions for the SPME sampling, such as the selectionof sampling fiber, sample pH, sampling temperature and time, microwave irradiation power, desorptiontemperature and time were investigated and then applied to real sample analysis. Experimental resultsindicated that the extraction of pyrethroids from a 20-mL aquatic sample (pH 4.0) was achieved with thebest efficiency through the use of a 100-μm PDMS fiber, microwave irradiation of 157 W and samplingat 30℃ for 10 min. Under optimum conditions, the detections were linear in the range of 0.05-0.5 μg/L with the square of correlation coefficients (R~2) of >0.9913 for pyrethroids except bifenthrin being 0.9812.Method-detection Iimits (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 fieldunderground water sample was analyzed with recovery between 88.5% to 115.5%. This method was provento be a very simple, rapid, and solvent-free process to achieve the sample pretreatment before the analysisof trace pyrethroids in aqueous samples by gas chromatography.