| Abstract
| - Oxygen isotope ratio determination on any of the waterphases (water vapor, water, ice) is of great relevance indifferent research fields such as climate and paleoclimatestudies, geological surveys, and hydrological studies. Theconventional technique for oxygen isotope measurementinvolves equilibration with carbon dioxide gas for a giventime with a subsequent isotope determination. The equilibration technique is available in different layouts, but allof them are rather time-consuming. Here we report a newon-line technique that processes water samples as wellas ice samples. The same principal, CO2 hydration, isused but speeded up by (i) a direct injection and fulldissolution of CO2 in the water, (ii) an increased isotopeexchange temperature at 50 °C, and (iii) a rapid gasextraction by means of an air-permeable membrane intoa continuous helium flux supplying the isotope ratio massspectrometer with the sample gas. The precision is betterthan 0.1‰ which is only slightly larger than with theconventional equilibration technique. This on-line technique allows analysis of 1 m of ice with a resolution of1−3 cm, depending on the meltwater flux, within 1 h.Similarly, continuous and fast analysis can be performedfor aqueous samples for hydrological, geological, andperhaps medical applications.
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