In this study a comprehensive approach for determination of low molecular organophosphorus nerve agent markers - highly polar alkylphosphonic acids and much less polar alkyl methylphosphonic acids is presented. Accurate, sensitive and simultaneous determination of the nerve agent markers in human urine was performed by ion chromatography and tandem mass spectrometry using deuterated internal standards. Analysis of the urine extracts was conducted on an anion-exchanger based on poly(styrene-co-divinylbenzene) substrate with a high degree of crosslinking and a covalently-bonded branched functional layer. The use of this type of column allowed achieving high values of retention factors for alkylphosphonic acids and alkyl methylphosphonic acids due to combination of anion-exchange and hydrophobic interactions between the analytes and the stationary phase of the column. Prior to the analysis, the urine samples were purified using anion-exchange cartridges for solid-phase extraction, and high recovery values were achieved for each analyte. The developed IC-MS/MS technique was validated for linearity, limit of detection, limit of quantification, precision and accuracy using two LC-MS/MS instruments. The proposed approach was successfully tested on the urine samples, provided by the Organisation for the Prohibition of Chemical Weapons in the frame of the 4th Biomedical Proficiency Test.
Keywords: Alkyl methylphosphonic acids; Alkylphosphonic acids; Ion chromatography; Nerve agent markers; Solid-phase extraction; Tandem mass spectrometry; Urine samples.
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