Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID, 83415, USA.
Graduate School of Engineering, Department of Applied Chemistry, Osaka University, Osaka, Japan.
J Am Soc Mass Spectrom. 2018 Oct;29(10):1963-1970. doi: 10.1007/s13361-018-2006-y. Epub 2018 Jun 28.
A new methodology for gas-phase uranium ion formation is described in which UO is dissolved in neat N-ethyl,N'-methylimidazolium fluorohydrogenate ionic liquid [EMIm][F(HF)], yielding a blue-green solution. The solution was diluted with acetonitrile and then analyzed by electrospray ionization mass spectrometry. UF (a U(V) species) was observed at m/z = 352, and other than cluster ions derived from the ionic liquid, nothing else was observed. When the sample was analyzed using infusion desorption chemical ionization, UF was the base peak, and it was accompanied by a less intense UF that most likely was formed by elimination of a fluorine radical from UF. Formation of UF required dissolution of UO followed by or concurrent with oxidation of uranium from the + 4 to the + 5 state and finally formation of the fluorouranate. Dissolution of UO produced a bright yellow solution indicative of a U(VI) species; however, electrospray ionization did not produce abundant U-containing ions. The abundant UF provides a vehicle for accurate measurement of uranium isotopic abundances free from interference from minor isotopes of other elements and a convenient ion synthesis route that is needed gas-phase structure and reactivity studies like infrared multiphoton dissociation and ion-molecule dissociation and condensation reactions. The reactive fluorohydrogenate ionic liquid may also enable conversion of uranium in oxidic matrices into uranium fluorides that slowly oxidize to uranyl fluoride under ambient conditions, liberating the metal for facile measurement of isotope ratios without extensive chemical separations. Graphical abstract ᅟ.
一种新的气相铀离子形成方法被描述，其中 UO 在纯 N-乙基，N'-甲基咪唑𬭩氟氢酸盐离子液体 [EMIm][F(HF)]中溶解，得到蓝绿色溶液。将溶液用乙腈稀释，然后通过电喷雾电离质谱进行分析。在 m/z = 352 处观察到 UF（一种 U(V)物种），除了源自离子液体的簇离子之外，没有观察到其他物质。当使用注入解吸化学电离对样品进行分析时，UF 是基峰，它伴随着一个不太强烈的 UF，很可能是通过从 UF 中消除氟自由基形成的。UF 的形成需要 UO 的溶解，随后或同时发生铀从 +4 价氧化到 +5 价，最后形成氟铀酸盐。UO 的溶解产生了亮黄色溶液，表明存在 U(VI)物种；然而，电喷雾电离并没有产生丰富的含铀离子。丰富的 UF 为准确测量铀同位素丰度提供了一种手段，不受其他元素的次要同位素的干扰，并且是气相结构和反应性研究（如红外多光子解离和离子-分子解离和缩合反应）所需的方便的离子合成途径。反应性氟氢酸盐离子液体还可能将氧化态基体中的铀转化为氟化铀，在环境条件下缓慢氧化为六氟铀酸盐，释放出金属，便于进行同位素比值的测定，而无需进行广泛的化学分离。
