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Oxidative degradation of bis(2,4,4‐trimethylpentyl)dithiophosphinic acid in nitric acid studied by electrospray ionization mass spectrometry
Author(s) -
Groenewold Gary S.,
Peterman Dean R.,
Klaehn John R.,
Delmau Laetitia H.,
Marc Philippe,
Custelcean Radu
Publication year - 2012
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.6339
Subject(s) - chemistry , electrospray ionization , nitric acid , mass spectrum , mass spectrometry , aqueous solution , dissociation (chemistry) , ion , electrospray , inorganic chemistry , collision induced dissociation , analytical chemistry (journal) , nuclear chemistry , chromatography , organic chemistry , tandem mass spectrometry
RATIONALE The selective separation of the minor actinides (Am, Cm) from the lanthanides is a topic of ongoing nuclear fuel cycle research, and dithiophosphinic acids are candidate ligands in these processes. Ligand instability has been noted under radiolytic and harsh acid conditions but explicit degradation pathways for ligands such as bis(2,4,4‐trimethylpentyl)‐dithiophosphinic acid (CyxH), the major compound in the commercial product Cyanex 301, have been elusive. METHODS Organic solutions of CyxH were contacted with aqueous solutions of HNO 3 , and their degradation was studied by analyzing samples from these experiments by direct infusion electrospray ionization mass spectrometry. Ions were identified using accurate mass measurement and collision‐induced dissociation. RESULTS The positive ion spectra contained cationized CyxH cluster ions, and oxidatively coupled species (designated Cyx 2 ) cationized by either H or Na. The Cyx 2 ‐derived ions increased with acid contact time. The negative ion spectra consisted almost entirely of the CyxH conjugate base. The negative ion spectra of the HNO 3 ‐contacted samples also contained conjugate bases corresponding to the dioxo and perthio derivatives of CyxH. CONCLUSIONS CyxH is oxidized by acid contact to form the coupled species Cyx 2 , and the dioxo species arise from subsequent oxidation of Cyx 2 . Oxidative coupling increases with contact time, and with higher HNO 3 concentrations. The direct infusion measurements provided a simple approach for assessing degradation pathways and kinetics. Copyright © 2012 John Wiley & Sons, Ltd.