Rapid determination of tritium and carbon-14 in urine samples using a combustion technique

Traditionally in bioassay monitoring, ³H determinations in urine have been performed using either direct counting (with or without sample decolourisation) or distillation whilst ¹⁴C has been determined on separate sub-samples following chemical isolation of the carbon from samples. Although these techniques are relatively straightforward they do not permit simultaneous determination of ³H/¹⁴C. For ³H, direct counting can be significantly affected by variations in sample composition/colour resulting in varying degrees of sample quench, does not distinguish between aqueous/organically-bound ³H and is limited to small sample sizes. This study describes the use of purpose built multi-tube combustion furnace for the simultaneous extraction and determination of ³H and ¹⁴C. The technique is insensitive to sample composition and can be adapted to measure Tritiated water (HTO) and organically bound tritium separately. The development of a multi-tube system with integrated cool-down facility permits rapid throughput of high sample numbers and has been proven effective in decommissioning waste characterisation. In addition, the furnace-based technique is capable of processing larger sample sizes, increasing analytical sensitivity and accuracy of dose assessment.