Quantification of organophosphorus nerve agent metabolites using a reduced-volume, high-throughput sample processing format and liquid chromatography-tandem mass spectrometry

Abstract

A reduced-volume, high-throughput analytical method has been developed for the quantification of organophosphorus (OP) nerve agent metabolites in human urine. Metabolites of soman, sarin, cyclohexyl-sarin, VX, and Russian-VX were quantified down to a lowest reportable limit of 1 ng/mL in human urine. One hundred microliter urine samples were preconcentrated using normal-phase 96-well solid-phase extraction silica sorbent beds. Dual-column hydrophilic interaction liquid chromatography was applied in a 2.5-min isocratic separation followed by negative electrospray isotope-dilution multiple-reaction-monitoring mass spectrometry. Method validation included the characterization of two synthetic urine pools, relative recovery experiments, and calculation of the method limit of detection. All liquid handling steps were processed in a high-density 96-well format, including sample aliquoting, extraction, dry-down, and reconstitution. This allows up to 3840 unknown samples, plus calibrators and quality control materials, to be prepared on a single liquid handler in a 24-h period. In a public health emergency involving OP-nerve agents, this method provides the sample preparation and analytical capacity to respond rapidly to a large number of patient samples.