Heumann Klaus G
Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University Mainz, 55099 Mainz, Germany.
Anal Bioanal Chem. 2004 Jan;378(2):318-29. doi: 10.1007/s00216-003-2325-z. Epub 2003 Nov 29.
This critical review discusses the conditions under which inductively coupled plasma-isotope dilution mass spectrometry (ICP-IDMS) is suitable as a routine method for trace element and element-speciation analysis. It can, in general, be concluded that ICP-IDMS has high potential for routine analysis of trace elements if the accuracy of results is of predominant analytical importance. Hyphenated techniques with ICP-IDMS suffer both from lack of commercially available isotope-labeled spike compounds for species-specific isotope dilution and from the more complicated system set-up required for species-unspecific ICP-IDMS analysis. Coupling of gas or liquid chromatography with species-specific ICP-IDMS, however, enables validation of analytical methods involving species transformations which cannot easily be performed by other methods. The potential and limitations of ICP-IDMS are demonstrated by recently published results and by some unpublished investigations by our group. It has been shown that possible loss of silicon as volatile SiF4 during decomposition of a sample by use of hydrofluoric acid has no effect on trace silicon determination if the isotope-dilution step occurs during digestion in a closed system. For powder samples, laser ablation ICP-IDMS can be applied with an accuracy comparable with that only available from matrix-matched standardization, whereas the accuracy of electrothermal vaporization ICP-IDMS was strongly dependent on the element determined. The significance of easy synthesis of isotope-labeled spike compounds for species-specific ICP-IDMS is demonstrated for monomethylmercury and Cr(VI). Isotope-exchange reactions between different element species can prevent the successful application of ICP-IDMS, as is shown for iodinated hydrocarbons. It is also shown for monomethylmercury that species transformations during sample-pretreatment steps can be followed by species-specific ICP-IDMS without loss of accuracy. A relatively simple and time-efficient procedure for determination of monomethylmercury in environmental and biological samples is discussed. The method, which entails a rapid microwave-assisted isotope dilution step and in-situ extraction of the derivatized species, has good potential for routine application in the future.
本批判性综述讨论了电感耦合等离子体质谱-同位素稀释质谱法(ICP-IDMS)适合作为痕量元素和元素形态分析常规方法的条件。一般而言,可以得出结论:如果结果的准确性是主要的分析重点,那么ICP-IDMS在痕量元素的常规分析方面具有很高的潜力。与ICP-IDMS联用的技术存在两个问题,一是缺乏用于特定物种同位素稀释的市售同位素标记的内标化合物,二是对于非特定物种的ICP-IDMS分析需要更复杂的系统设置。然而,气相或液相色谱与特定物种的ICP-IDMS联用,能够验证涉及物种转化的分析方法,而这是其他方法难以轻易实现的。最近发表的结果以及我们小组一些未发表的研究证明了ICP-IDMS的潜力和局限性。结果表明,在封闭系统中消化样品时,如果在消化过程中进行同位素稀释步骤,那么使用氢氟酸分解样品时可能以挥发性SiF4形式损失的硅对痕量硅的测定没有影响。对于粉末样品,激光烧蚀ICP-IDMS的应用精度可与仅通过基体匹配标准化获得的精度相媲美,而电热蒸发ICP-IDMS的精度强烈依赖于所测定的元素。对于甲基汞和Cr(VI),证明了易于合成用于特定物种ICP-IDMS的同位素标记内标化合物的重要性。不同元素物种之间的同位素交换反应可能会阻碍ICP-IDMS的成功应用,碘化烃的情况就是如此。对于甲基汞还表明,样品预处理步骤中的物种转化可以通过特定物种的ICP-IDMS进行跟踪,而不会损失精度。讨论了一种相对简单且省时的测定环境和生物样品中甲基汞的方法。该方法包括快速微波辅助同位素稀释步骤和衍生化物种的原位萃取,未来在常规应用方面具有良好的潜力。