Abstract The analytical procedures for accurate quantification of selenomethionine (SeMet) at various concentration levels and in different matrix of certified reference materials (CRMs): ERM DB151 skimmed powder milk, ERM DC210a wheat flour and SELM 1 enriched yeast were developed and compared. Two modes of application of isotope dilution, namely species-specific isotope dilution analysis (IDA) and species-unspecific isotope dilution analysis with the use of high performance liquid chromatography (HPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) were evaluated. The excellent results for SeMet were obtained in this study, using of developed species-specific ID HPLC ICP-MS and addition of spike solution before extraction. With this approach, the stability of SeMet during sample preparation or sample storage can be track. It was also possible to state the presence or absence of SeMet in oxidized form, which was co-eluted with the other selenium species. Moreover, the origin of SeMetO in extracts can be confirmed by the calculation and comparison of isotope ratios from SeMet and SeMetO signals. Equal altered isotope ratios in both species indicate that SeMetO was formed during extraction or storage of sample and SeMet is only source of SeMetO. Although, different isotopic ratios can indicate that the signal also comes from SeMetO already present in the sample. All results obtained for SeMet by species-unspecific ID HPLC ICP-MS, were close to the certified reference values within their uncertainty, under the condition, when 2-mercaptoethanol was added before extraction as antioxidant agent. The species-specific and species-unspecific IDA HPLC ICP-MS approaches were validated and both can be used to establish references values and accurate quantification of selenomethionine in food related products at various concentration level. Moreover, in the case of species-specific IDA, which although is much more time-consuming than species-unspecific IDA, the origin of SeMeO in extracts can be clearly indicated.

中文翻译：

---

高效液相色谱物种特异性和物种非特异性同位素稀释电感耦合等离子体质谱的比较研究。硒代蛋氨酸的案例研究及其氧化形式的起源

摘要 开发并比较了在不同浓度水平和不同标准物质 (CRM) 基质中准确定量硒代甲硫氨酸 (SeMet) 的分析程序：ERM DB151 脱脂奶粉、ERM DC210a 小麦粉和 SELM 1 富集酵母。对同位素稀释的两种应用模式，即物种特异性同位素稀释分析 (IDA) 和物种非特异性同位素稀释分析，使用高效液相色谱 (HPLC) 与电感耦合等离子体质谱 (ICP-MS) 耦合进行了评估. 本研究使用开发的物种特异性 ID HPLC ICP-MS 并在萃取前添加加标溶液，在本研究中获得了出色的 SeMet 结果。通过这种方法，可以跟踪样品制备或样品储存过程中 SeMet 的稳定性。也可以说明是否存在氧化形式的 SeMet，它与其他硒物质共流出。此外，提取物中 SeMetO 的来源可以通过计算和比较来自 SeMet 和 SeMetO 信号的同位素比来确认。两个物种中相同的改变同位素比率表明 SeMetO 是在样品的提取或储存过程中形成的，而 SeMet 只是 SeMetO 的来源。虽然，不同的同位素比率可以表明信号也来自样品中已经存在的 SeMetO。在提取前添加 2-巯基乙醇作为抗氧化剂的条件下，通过物种非特异性 ID HPLC ICP-MS 获得的所有 SeMet 结果在其不确定性范围内接近认证参考值。物种特异性和物种非特异性 IDA HPLC ICP-MS 方法经过验证，两者均可用于建立参考值和准确定量食品相关产品中不同浓度水平的硒代蛋氨酸。此外，在物种特异性 IDA 的情况下，虽然比物种非特异性 IDA 耗时得多，但可以清楚地表明提取物中 SeMeO 的来源。