Determination of methylphosphonic acid and alkyl methylphosphonic acid esters in soils by liquid chromatography-high-resolution mass spectrometry (LC-HRMS)

Abstract

We have optimized the method for simultaneous extraction of ethyl methylphosphonic acid ester (EMPA), isopropyl methylphosphonic acid ester (IPMPA), isobutyl methylphosphonic acid ester (IBMPA), pinacolyl methylphosphonic acid ester (PMPA), and methylphosphonic acid (MPA) from soil with their further determination by high performance liquid chromatography — high-resolution tandem mass spectrometry (HPLC — HRMS/MS). The analytes are highly-polar products of nerve agent hydrolysis. The observed ions in the fragmentation mass spectra of deprotonated molecules of EMPA, IPMPA, IBMPA, PMPA, MPA, and their corresponding deuterated molecules, as well as possible structural formulas of fragment ions are presented. Liquid extraction with deionized water followed by concentration by evaporation is used to prepare soil samples for analysis. Separation of the components was carried out using reverse-phase chromatography. The time required for sample preparation and analysis of soil samples does not exceed 1 hour. The detection limits in soil were 0.05 ng/g for EMPA and IPMPA, 0.02 ng/g for IBMPA and PMPA, and 1 ng/g for MPA.