Mixed-mode C-C18 monolithic spin-column extraction and GC-MS for simultaneous assay of organophosphorus compounds, glyphosate, and glufosinate in human serum and urine

A rapid and specific method for simultaneous quantitation of organophosphates [fenitrothion (MEP), malathion (MAL), and phenthoate (PAP)], glyphosate (GLYP), and glufosinate (GLUF) in human serum and urine by gas chromatography-mass spectrometry (GC-MS) was validated. All targeted compounds, together with the internal standards [fenitrothion-d (6) (MEP-d (6)) and dl-2-amino-3-phosphonopropionic acid (APPA)], were extracted from the serum and urine with a mixed-mode C-C-18 monolithic spin column. Extracted samples were derivatized with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) containing 1% tert-butyldimethylchlorosilane (TBDMCS). Linear calibration curves for serum and urine spanned the ranges of 0.1-10.0 mu g/ml for organophosphates, 10-100.0 mu g/ml for GLYP, and 5-100.0 mu g/ml for GLUF. Detection limits for serum and urine were 10 and 5 mu g/ml for GLYP and GLUF, respectively, and quantitation limits for serum and urine were 10 and 5 mu g/ml for GLYP and GLUF, respectively. Both detection and quantitation limits for serum and urine were 0.1 mu g/ml for organophosphates. The intra-assay and interassay accuracy and precision (expressed as relative standard deviation, %RSD) evaluated for all compounds were within 96.5-109.5% and 5.9-13.1%, respectively. The recovery of organophosphates from serum and urine, spiked at concentrations of 0.1, 1.5, 5, and 9 mu g/ml, ranged from 58.8 to 90.8%. Recovery of GLYP and GLUF from serum and urine, spiked at concentrations of 10 (serum) or 5 (urine), 15, 50, and 90 mu g/ml, ranged from 2.6 to 6.9%. This method had a chromatographic run time of 16.0 min. The validated method was successfully applied to a clinical case of GLYP poisoning.