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

Tritium (³H) 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 2 L of a water sample. This allows a high enrichment factor (>100) for measuring low ³H contents of <0.05 TU. The TEU uses a small cell (250 mL) with automated re-filling and a CO₂ 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 ²H concentrations with laser spectrometry.