Extraction technique for the determination of oxygen-18 in water using preevacuated glass vials.
Extraction technique for the determination of oxygen-18 in water using preevacuated glass vials.
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DOI：
10.1021/ac00031a026
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发表时间：
1992-04
影响因子：
7.4
通讯作者：
R. Socki;H. Karlsson;Everett K. Gibson
中科院分区：
文献类型：
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作者：
R. Socki;H. Karlsson;Everett K. Gibson
通过在医学科学和水文学中的应用，最近出现了对用于从水中常规提取18 O/16 O的快速、廉价技术的需求。传统的测定水的氧同位素组成的实验技术，CO2-H2O平衡法，是繁琐，耗时，并涉及使用定制的玻璃仪器。此外，由于一个样品与下一个样品之间的潜在记忆效应，玻璃器皿需要在运行之间彻底清洁。已经进行了一些尝试来改进该方法。直接在质谱仪的源中分析水的尝试产生了很大的记忆效应和可疑的结果。用于从水中自动提取18 O/16 O的市售设备通常非常昂贵，并且通常被设计成仅与制造商自己的质谱仪连接。本文所述的方法利用廉价的现成的预抽真空玻璃小瓶。预抽真空瓶已被其他人用于呼吸CO2的同位素分析，并得到了很好的测试。小瓶可以以相对较低的成本从科学仪器供应商处批量购买。这些设备与由不锈钢注射器针头和玻璃冷阱组成的简化提取管线相结合。将小瓶填充CO2和H2O，并在恒温水浴中摇动至少90 min。由于小瓶在使用后丢弃，因此无需清洁，基本上消除了任何记忆效应。重现性通常优于+/-0.05%。所需的唯一试剂是用于平衡的气态CO2、用于捕获水的干冰/酒精混合物和用于转移CO2的液氮。
The need for a rapid, inexpensive technique for routine 18O/16O extraction from water has arisen recently through applications in the medical sciences and in hydrology. The traditional experimental technique for determining the oxygen isotope composition of water, the CO2-H2O equilibration method, is tedious, time consuming, and involves the use of custom-made glass apparatus. Furthermore, because of potential memory effects from one sample to the next, the glassware needs to be thoroughly cleaned between runs. A few attempts have been made to improve upon the method. Attempts to analyze water directly in the source of the mass spectrometer produced large memory effects and questionable results. Commercially available apparatus for automated extraction of 18O/16O from water is generally prohibitively expensive and often is designed to interface only with the manufacturer's own mass spectrometer. The method described in this paper utilizes inexpensive, off-the-shelf, preevacuated, glass vials. Preevacuated vials have been used by others for the isotopic analysis of breath CO2 and are well tested. The vials can be purchased in bulk from scientific apparatus suppliers at a relatively low cost. These are coupled with a simplified extraction line consisting of a stainless steel syringe needle and a glass cold trap. Vials are filled with CO2 and H2O and shaken in a constant-temperature water bath for at least 90 min. Since the vials are discarded after use, no cleaning is necessary, essentially eliminating any memory effect. Reproducibility is generally better than +/- 0.05%. The only reagents required are gaseous CO2 for equilibration, a dry ice/alcohol mixture for trapping water, and liquid nitrogen for transferring the CO2.