Background

The urinary excreted selenium species selenosugar 1 (SeSug1) plays a key role for monitoring of supplemental selenium exposure, e.g. by occupational exposure. In order to reproduce its contents in the long term, the integrity of SeSug1 in the urine is essential. Studies on the stability of SeSug1 in urine samples stored at −20 °C have shown that degradation of SeSug 1 occurs, requiring adequate countermeasures.

Methods

Here, we explored the long-term stability of SeSug1 under usual storage conditions at −20 °C. For this purpose, the simultaneous determination of selenosugar 1 and methylselenic acid (MeSeA) was used to explore the stabilizing of the SeSug1 content by applying sodium azide (NaN₃) as a bactericide or/and 5 M ammonium acetate buffer for pH control.

Results

In untreated urine, conversion of SeSug1 to MeSeA was evident within days. Differences in urine matrices clearly showed different impact, which could be attributed to different buffer strengths by the urine itself. For durability, various concentrations of sodium azide were first applied, followed by pH buffering. A combination of 0.1% NaN₃ and pH of 5.5 kept the SeSug1 content stable for over 3 months.

Conclusion

The formation of MeSeA as degradation product of SeSug1 could be confirmed. Based on the proportions, an oxidation-based decomposition pathway was proposed. The investigations revealed that the complex interaction of pH buffering and bactericidal activity must be taken into account in order to stabilize SeSug1 in the urine. The main effect was the addition of NaN₃. However, the alkaline nature of NaN₃ required a sufficient buffering of the urinary matrix at a pH of 5.5.

中文翻译：

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人体硒代谢的主要消除产物甲基-2-乙酰胺-2-脱氧-1-硒-β-d-吡喃半乳糖苷（硒糖1）尿液排泄的不稳定性及其稳定措施。

 背景

尿中排出的硒种类硒糖 1 (SeSug1) 在监测补充硒暴露（例如职业暴露）方面发挥着关键作用。为了长期复制其内容物，尿液中 SeSug1 的完整性至关重要。对-20 °C 下储存的尿液样本中 SeSug1 稳定性的研究表明，SeSug 1 会发生降解，需要采取适当的对策。

 方法

在这里，我们探讨了 SeSug1 在 -20 °C 的通常储存条件下的长期稳定性。为此，通过同时测定硒糖1和甲基硒酸（MeSeA），探索使用叠氮化钠（NaN ₃ ）作为杀菌剂或/和5 M醋酸铵缓冲液进行pH控制来稳定SeSug1含量。

 结果

在未经处理的尿液中，SeSug1 到 MeSeA 的转化在几天内就很明显。尿液基质的差异清楚地显示出不同的影响，这可能归因于尿液本身的不同缓冲强度。为了耐久性，首先使用不同浓度的叠氮化钠，然后进行 pH 缓冲。 0.1% NaN ₃和 pH 5.5 的组合使 SeSug1 含量保持稳定超过 3 个月。

 结论

可以确认作为SeSug1的降解产物MeSeA的形成。根据比例，提出了基于氧化的分解途径。研究表明，为了稳定尿液中的 SeSug1，必须考虑 pH 缓冲和杀菌活性的复杂相互作用。主要作用是NaN ₃的添加。然而，NaN ₃的碱性性质需要在pH 5.5 下对尿基质进行充分缓冲。