ABSTRACT A novel method of the accelerated equilibration of 18O between CO2 and H2O for the measurement of the 18O/16O isotope ratios in aqueous samples with natural isotope abundances is presented. This rapid equilibrium method is based on the in vitro application of the enzyme carbonic anhydrase (CA). The CA from bovine erythrocytes was adsorptively fixed to 3-mm glass beads with an etched surface. After the addition of this carrier-fixed CA catalyst to the water sample, the isotope equilibrium was already reached after 1 h. The previously used non-catalysed 18O isotope exchange in water samples needs about 24 h. Whole blood samples also showed fast 18O isotope equilibration, which definitely results from the native presence of CA in erythrocytes. By shortening the time for sample preparation, the CA catalysed technique can significantly increase the throughput of the samples to be measured, and also 18O and 2H measurement by means of isotope ratio mass spectrometry (IRMS) may be synchronized. The 2H and 18O sample preparation can be performed in the same reaction vessel because cross-effects at the simultaneous use of Pt and CA catalysts do not occur.

中文翻译：

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体外应用碳酸酐酶加速 H2O 和 CO2 之间 18O 的平衡，以快速测量水样中的 18O/16O 同位素比

摘要 提出了一种在 CO2 和 H2O 之间加速 18O 平衡的新方法，用于测量具有天然同位素丰度的水样中的 18O/16O 同位素比。这种快速平衡方法基于酶碳酸酐酶 (CA) 的体外应用。来自牛红细胞的 CA 被吸附固定到具有蚀刻表面的 3 毫米玻璃珠上。将这种载体固定的 CA 催化剂添加到水样中后，1 小时后已达到同位素平衡。以前在水样中使用的非催化 18O 同位素交换需要大约 24 小时。全血样本还显示出快速的 18O 同位素平衡，这肯定是由于红细胞中天然存在的 CA。通过缩短样品制备时间，CA 催化技术可以显着提高待测样品的通量，并且可以同步通过同位素比质谱 (IRMS) 进行的 18O 和 2H 测量。2H 和 18O 样品制备可以在同一反应容器中进行，因为在同时使用 Pt 和 CA 催化剂时不会发生交叉效应。