Cold column trapping-headspace micro-solid phase extraction for efficient preconcentration and GC-MS determination of pesticides in soil
A new cold column trapping-headspace micro-solid phase extraction (CCT-HS-μSPE) system was developed and used for the preconcentration and GC-MS determination of three pesticides (diazinon, malathion and permethrin) in soil samples. For efficient extraction of the analytes using the CCT-HS-μSPE system, several parameters influencing the performance of the technique were carefully studied and optimized through a simplex optimization method. During the sampling, the temperature of the CCT containing the adsorbent was lowered down to 0 °C using a pair of thermoelectric cooler modules. This increased the adsorption efficiency of the analytes by increasing the temperature gap between the sample and the adsorption phase. The best results were obtained using only 10 mg of amino-functionalized SBA-15 sorbent with the sample being heated at 75 °C for 11.3 min during which its headspace vapor was circulating in the system. The desorption was achieved with 80 μL acetonitrile by setting the CCT temperature to 20 °C. Under the optimized conditions, linear calibration curves were obtained for the analytes within a range of 2.5–3.5 ng g−1 up to 7000 ng g−1, with determination coefficients that ranged from 0.975 to 0.977. The limits of detection were between 0.89 and 1 ng g−1, and the coefficients of variation for 6 replicates were between 4.1 and 5.6%. The method was successfully applied to the GC-MS analysis of pesticides in soil samples.