A compact tritium enrichment unit for large sample volumes with automated re-filling and higher enrichment factor.

Tritium (H) in natural waters is a powerful tracer of hydrological processes, but its low concentrations require electrolytic enrichment before precise measurements can be made with a liquid scintillation counter. Here, we describe a newly developed, compact tritium enrichment unit which can be used to enrich up to 2L of a water sample. This allows a high enrichment factor (>100) for measuring low H contents of <0.05TU. The TEU uses a small cell (250mL) with automated re-filling and a CO bubbling technique to neutralize the high alkalinity of enriched samples. The enriched residual sample is retrieved from the cell under vacuum by cryogenic distillation at -20°C and the tritium enrichment factor for each sample is accurately determined by measuring pre- and post- enrichment H concentrations with laser spectrometry.