Uranium in Urine: Quantification and Isotope Ratio Determination

While the quantification of uranium is therefore demanding in the diluted sample, uranium isotope ratio determination requires the ultimate in instrumental performance as good precisions for large isotope ratios are required at low concentrations. The abundances of the three naturally occurring U isotopes are shown in Table 1, together with the 234U/238U and 235U/238U ratios. The nuclear industry removes the majority of 235U and 234U for use in nuclear fuel rods, leaving behind “depleted uranium” (DU). This material typically has a 235U/238U ratio of 0.0025, and therefore an increased 238U abundance of approximately 99.75%. In the diluted urine sample matrix however, this analysis is further complicated as minute contaminations of isotopically enriched or depleted uranium must be identified in a much larger quantity of isotopically normal uranium – all this at the pg g-1 level. This report summarizes examples of both concentration and isotopic uranium analyses in urine. All analyses were performed on the Thermo Scientific ELEMENT 2, a single collector double focusing ICP-MS that provides high sensitivity, low background, an extended dynamic range (pre-requisites for quantification over a wide range of uranium concentrations) and flat top peaks (required for precise and accurate isotope ratio measurements). The detection range and isotope capabilities of such instrumentation allow the monitoring of uranium related environmental pollution from natural uranium, DU (munitions, armor) or enriched uranium (nuclear processing plants) by analyzing total uranium content or/and its isotopic composition.