Determination of four phosphorothioate pesticide residues in soil samples by molecularly imprinted matrix solid-phase dispersion combined with high performance liquid chromatography

An effective and selective method for sample pretreatment, namely molecularly imprinted matrix solid-phase dispersion coupled with high performance liquid chromatography(HPLC), was developed for rapid determination of four phosphorothioate pesticides(tolclophos-methyl, chlorpyrifos, parathion-methyl, chlorpyriphos-methyl) in soil samples. New molecularly imprinted polymer microspheres(MIPs) were synthesized with precipitation blotting polymerization by using structural analogue tolclofos-methyl as template molecule and employing methacrylic acid(MAA) and ethylene glycol dimethacrylate(EDMA) as the functional monomer and cross-linker agent, and azodiisobutyronitrile as initiator. Furthermore, the molar ratio of template to functional monomer was at 1:4 in this experiment. The results indicated that the MIPs showed a special binding ability for the template and some absorbability to three other phosphorothioate pesticides(chlorpyrifos, parathion-methyl, chlorpyriphos-methyl). The obtained MIPs was used to extract and preconcentrate four phosphorothioates as adsorbent of matrix solid phase dispersion from extracting solution of soil, then the samples were detected by HPLC. The optimized method parameters were as follows: acetonitrile and pure water including 0.1% acetic acid(V/V=3/1) were selected as mobile phase, flow rate was 0.8 mL/min, sample injection voplume was 20 μL, UV detecting wavelength was 210 nm, and Eclipse XDB-C8 column(150 mm×4.6 mm,5 μm)was used as separating column with column temperature of 25 ℃. The linear correlation was 0.997 5-0.999 8 between concentrations range of 0.01-5.0 mg/kg. The detection limit of the method was 0.452-1.226 μg/kg in soil samples. With relative standard deviations of 2.8%-7.3% in soil samples, the fortified tests showed recovery rates were in the range of 76%-96% in soil samples. This study indicated that the proposed method could meet the requirements for simultaneously determinationg of phosphorothioate pesticide residues in soil.