Idaho National Laboratory, 2351 North Boulevard, Idaho Falls, ID 83415-2208, USA.
Rapid Commun Mass Spectrom. 2012 Oct 15;26(19):2195-203. doi: 10.1002/rcm.6339.
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.
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.
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.
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.
从镧系元素中选择性分离次锕系元素（Am、Cm）是当前核燃料循环研究的课题，而二硫代膦酸是这些过程中的候选配体。在辐射和苛刻酸条件下已经注意到配体的不稳定性，但对于配体（如双（2,4,4-三甲基戊基）二硫代膦酸（CyxH），商业产品 Cyanex 301 中的主要化合物）的明确降解途径一直难以捉摸。
将 CyxH 的有机溶液与 HNO3 的水溶液接触，并通过直接注入电喷雾电离质谱分析这些实验的样品来研究其降解。使用精确质量测量和碰撞诱导解离来鉴定离子。
正离子谱包含 CyxH 簇离子的阳离子化，以及通过 H 或 Na 阳离子化的氧化偶联物质（指定为 Cyx(2)）。Cyx(2)衍生的离子随酸接触时间增加而增加。负离子谱几乎完全由 CyxH 共轭碱组成。与 HNO3 接触的样品的负离子谱还含有 CyxH 的二氧代和过硫代衍生物的共轭碱。
CyxH 通过酸接触被氧化形成偶联物质 Cyx(2)，而二氧代物质则来自 Cyx(2)的后续氧化。氧化偶联随接触时间和较高的 HNO3 浓度而增加。直接注入测量为评估降解途径和动力学提供了一种简单的方法。
