ABSTRACT

Some practical aspects were investigated for an on-line chromium reduction technique for measurement of D/H variations of natural waters using a conventional isotope ratio mass spectrometer. They include the configuration of the reaction system, the precautions taken before mass spectrometric measurement, the reproducibility of δD measurement, memory effects and salt effects. Approximately 150 water samples of 2 μl can be run with Cr powder (60 mesh) weighing approximately 16 g mixed with quartz glass sand (10 mesh). The mixture functions to avoid choking of the Cr reactor due to volume increase as Cr oxidation proceeds. The Cr powder-quartz glass sand mixture is placed in the middle of a quartz glass reaction tube and heated to >800°C. The reproducibility is ca. ±0.5‰ if care is taken for the above precautions and memory effects. This system can be easily installed on a conventional IRMS at low cost.