Molecularly imprinted solid phase extraction of urinary diethyl thiophosphate and diethyl dithiophosphate and their analysis by gas chromatography-mass spectrometry

Abstract

An analytical method involving molecularly imprinted solid phase extraction (MISPE) and gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of organophosphates metabolites (diethyl thiophosphate--DETP and diethyl dithiophosphate - DEDTP) in human urine samples. A DETP molecularly imprinted polymer (MIP) was synthesized using 4-vinylpiridine as the functional monomer and ethylene glycol dimethacrylate as the cross-linker. The conditioning step of the MISPE was conducted by running 3 mL of acetonitrile, 3 mL of 0.1 mol L⁻¹ dibasic phosphate buffer at pH 11 and 2 mL of water through the molecularly imprinted polymer (MIP) cartridge. The extraction step was executed using 1.0 mL of a urine sample, with the pH previously adjusted to 3.0. Finally, the analytes were eluted with 3 mL of acetonitrile and derivatized with 3% 2,3,4,5,6-pentafluorobenzyl bromide solution at room temperature for 1h. The sample was analyzed by GC-MS in the SIM (selected ion monitoring) mode. Analytical calibration curves for DETP and DEDTP were constructed using a pool of urine samples and six levels of concentration. The method was found to be linear from 10 to 500 μg L⁻¹ (r>0.99) with limits of quantification of 10 μg L⁻¹ for both analytes. The within-day and between-day precisions were evaluated (as %RSD) and all the results were <15% for both analytes. The method was accurate (relative error<±15%), with good robustness.