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–C₁₈ 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 μg/ml for organophosphates, 10–100.0 μg/ml for GLYP, and 5–100.0 μg/ml for GLUF. Detection limits for serum and urine were 10 and 5 μg/ml for GLYP and GLUF, respectively, and quantitation limits for serum and urine were 10 and 5 μg/ml for GLYP and GLUF, respectively. Both detection and quantitation limits for serum and urine were 0.1 μg/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 μg/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 μg/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.