电喷雾串联质谱快速鉴别水溶液中铀酰形态及在柠檬酸铀酰形态研究的应用

Rapid Identification of Uranyl Speciation in Solution by Electrospray Ionization Tandem Mass Spectrometry and Speciation Research of Uranyl Citrate

铀酰是含铀化合物基本官能团,分析出铀酰基团即证明化合物中含铀。本研究采用电喷雾串联质谱技术建立了一种快速鉴别水溶液含铀分子的方法。通过调控碰撞能量和质荷比,使样品离子在串联质谱碰撞池中被200 V的高碰撞能量碰撞诱导解离,将是否获得[UO_2]^+(m/z 269.9)质谱峰作为鉴别含铀分子的依据。以此方法分析柠檬酸-硝酸铀酰溶液,发现存在16种柠檬酸铀酰和5种无机铀酰形态。各柠檬酸铀酰形态中每个铀酰基团可紧密结合一个柠檬酸阴离子,并以较弱方式结合1个以上柠檬酸分子,形成单铀酰络合物。结果表明,柠檬酸铀酰形态络合键能大小顺序为:铀酰间键能>柠檬酸阴离子-铀酰键能>柠檬酸分子-铀酰键能;存在[(UO_2H_2Cit)_2H_3Cit]^(2+)双电荷双铀酰聚合的柠檬酸铀酰离子。本方法鉴定含铀物质无需复杂的结构解析或标准物质,提高了质谱鉴别铀形态的能力和效率,可望用于环境样品中柠檬酸铀酰形态的分析,对其它重金属有机形态质谱研究也具有很好的借鉴意义。在此过程中,高能量轰击[UO_2OH]^+通过可控的粒子碰撞方式制备出U(Ⅰ),是分离、提纯铀的一种可能途径。

By regulating collision energy and mass-to-charge ratio,a rapid identification method for uranium-containing compounds from aqueous solutions was established by electrospray ionization tandem mass spectrometry.At high collision energy of 200 V in collision-induced dissociation mode,target ions were bombarded to generate product ions which were subsequently analyzed whether there was mass spectrum peak of[UO2]^+(m/z 269.9),thus identifying the existence of uranium-containing molecules because[UO2]^+was their basic functional group.Based on this method,16 uranyl citrate and 5 inorganic uranyl speciation were identified in the citric acid-uranyl nitrate solution.Each uranyl group could bind a citrate anion tightly and complex weakly more than one citric acid molecule to form mono uranyl complex.Experiment result showed the following sequence of uranyl citrate complex bond energies:uranyl bond energy>citrate anion-uranyl bond energy>citric acid molecule-uranyl bond energy,and it was also found speciation of double-charged and double-uranyl ions,of which the fragmentation pathways needed further analysis.The method used in here unnecessarily required interpretation of mass spectra or standards of uranium,which would further demonstrate the utility of ESI-MS and its applicability to analyze uranyl-citrate speciation of environmental samples.It improved the identifying ability and efficiency of uranium speciation greatly,which provided reference significance for the study of other heavy metal organic speciation.Meanwhile,U was split from[UO2OH]^+ by controlled particle collision,which provided a possible way to separate and purify uranium.