Improved sample preparation of glyphosate and methylphosphonic acid by EPA method 6800A and time‐of‐flight mass spectrometry using novel solid‐phase extraction

Abstract

The employment of chemical weapons by rogue states and/or terrorist organizations is an ongoing concern in the United States. The quantitative analysis of nerve agents must be rapid and reliable for use in the private and public sectors. Current methods describe a tedious and time-consuming derivatization for gas chromatography-mass spectrometry and liquid chromatography in tandem with mass spectrometry. Two solid-phase extraction (SPE) techniques for the analysis of glyphosate and methylphosphonic acid are described with the utilization of isotopically enriched analytes for quantitation via atmospheric pressure chemical ionization-quadrupole time-of-flight mass spectrometry (APCI-Q-TOF-MS) that does not require derivatization. Solid-phase extraction-isotope dilution mass spectrometry (SPE-IDMS) involves pre-equilibration of a naturally occurring sample with an isotopically enriched standard. The second extraction method, i-Spike, involves loading an isotopically enriched standard onto the SPE column before the naturally occurring sample. The sample and the spike are then co-eluted from the column enabling precise and accurate quantitation via IDMS. The SPE methods in conjunction with IDMS eliminate concerns of incomplete elution, matrix and sorbent effects, and MS drift. For accurate quantitation with IDMS, the isotopic contribution of all atoms in the target molecule must be statistically taken into account. This paper describes two newly developed sample preparation techniques for the analysis of nerve agent surrogates in drinking water as well as statistical probability analysis for proper molecular IDMS. The methods described in this paper demonstrate accurate molecular IDMS using APCI-Q-TOF-MS with limits of quantitation as low as 0.400 mg/kg for glyphosate and 0.031 mg/kg for methylphosphonic acid.

Analysis of glyphosate and aminomethylphosphonic acid in water, plant materials and soil

“…Various methods have been used to compensate for or eliminate matrix effects, such as additional clean‐up steps, performing matrix‐matched calibration or using an extrapolative dilution approach . Occasionally, isotope‐labeled glyphosate and AMPA standards have been used in analyses with MS and MS/MS, which eliminate concerns of incomplete elution from SPE cartridges, sorbent effects and MS drift …”

“…However, to conduct the necessary research, simple, sensitive methods of analysis are required for glyphosate and AMPA in water, plant materials and soil samples. In addition to the environmental applications of such methods, it has been suggested that methods developed for glyphosate can be used for analysis of chemical weapons such as phosphonic acid‐containing nerve agents for which glyphosate has been used as a surrogate . While numerous reliable and sufficiently sensitive analytical techniques used to quantify glyphosate have been published since its introduction, they are, for the most part, rather complex and time consuming in order to compensate for glyphosate's chemical properties (e.g.…”

Simplified analysis of glyphosate and aminomethylphosphonic acid in water, vegetation and soil by liquid chromatography–tandem mass spectrometry

“…To facilitate glyphosate research, simple, sensitive methods of analysis are needed for glyphosate in water, plant and soil samples. In addition, it has been suggested that the simple, sensitive methods developed for glyphosate can be used for analysis of chemical weapons such as phosphonic‐acid‐containing nerve agents; glyphosate has been used as a surrogate for these chemicals …”

“…In addition, it has been suggested that the simple, sensitive methods developed for glyphosate can be used for analysis of chemical weapons such as phosphonic-acid-containing nerve agents; glyphosate has been used as a surrogate for these chemicals. 2 Numerous analytical techniques used to quantify glyphosate have proven to be reliable and sufficiently sensitive for most purposes. However, most of the methods are rather complex and time consuming, which leads to numerous 'new' or 'revised' methods being reported every year in the literature for water, plants or soil.…”

Sensitive and stable pre-calibrated solid-phase extraction columns for environmental and forensic quantification using isotope dilution mass spectrometry

“…22 This mass bias factor was applied as a correction factor to the isotope signals in the IDMS equation, as given by the following equation: 10 Samples of 4.0 mL of the mixture of working solutions containing both natural and isotopically enriched analytes at 20.0 ng mL À1 were analyzed (n ¼ 28) to determine mean signal intensities for each natural and each isotopic analyte.…”