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Characterization of alkylphosphonic acid vapors using atmospheric flow tube–ion trap mass spectrometry
Author(s) -
Morrison Kelsey A.,
Clowers Brian H.
Publication year - 2018
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8177
Subject(s) - chemistry , mass spectrometry , chromatography , hydrolysis , organic chemistry
Rationale A key aspect of detecting hazardous compounds at ultra‐trace levels for processing, compliance, and clean‐up purposes involves developing methods that are not only sensitive, but also highly selective with minimal sampling effort. Atmospheric flow tube mass spectrometry (AFT‐MS) using dielectric barrier discharge ionization has emerged as a technique that combines such features for vapor detection. AFT‐MS is thus appealing for application to ambient screening for chemical warfare agents (CWAs) and their degradation products. Initial characterization of AFT‐MS for CWA detection necessitates examining less harmful simulant species. A predominant hydrolysis product of most organophosphorus CWAs is methylphosphonic acid and most other hydrolysis products consist of some form of an alkylphosphonic acid. Methods An application of AFT‐MS is presented wherein a homologous series of four alkylphosphonic acids (methyl‐, ethyl‐, propyl‐, and t ‐butylphosphonic acid) were first qualitatively evaluated as anionic clusters with nitrate. These anionic adducts were subsequently quantified from non‐equilibrium headspace vapor sampled over alkylphosphonic acid solutions in methanol. Results The series of phosphonic acids demonstrated consistent relative ion abundances thought to be related at least in part to the relative vapor pressures depending on their alkyl chains. For quantitation, the resulting linear ranges were found to be 2 to 50 ppm soln for methylphosphonic acid, 5 to 50 ppm soln for ethylphosphonic acid, and 2 to 25 ppm soln for propylphosphonic acid and t ‐butylphosphonic acid; quality controls of 15 ppm soln were used to assess the quantitation accuracy. Conclusions Although measured over a limited dynamic range, the real‐time analysis afforded by this method suggests the feasibility of using thermodynamically stable anionic adducts to monitor organophosphorus compounds via AFT‐MS. In addition, this is proof‐of‐concept for the use of this ambient sensing technique to detect phosphonic acids. Furthermore, a discussion is included regarding gaps in clustering thermodynamics literature that would assist in uncovering physical or chemical explanations for observed trends.