科研之友
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摘要
Determination of uranium isotopes in urine is critical for distinguishing between exposure to natural and anthropogenic sources of uranium. In biomonitoring, the extremely low levels of total uranium [U] present in urine and the complexity of the urine matrix present challenges to accurate isotope ratio determination. We have validated a method for measurement of U-234/U-238, U-235/U-238 and U-236/U-238 in small-volume, random urine samples at occupational exposure levels, as well as for measurement of U-235/U-238 at biomonitoring levels. The method has been developed to detect exposure to mixtures of enriched and depleted uranium (DU) among former workers and nearby residents of the NL Industries factory in Colonie, NY, USA. Validation experiments employing solid phase extraction followed by SF-ICP-MS analysis were performed on base urine spiked with isotopic certified reference materials, isotopically depleted urine quality control materials, and natural uranium urine pools. Our results show that extraction with UTEVA resin yields lower blank levels than with TRU resin, and that double washing of the UTEVA resin columns results in further lowering of the blank. At occupational exposure levels ([U] = 50 ng L-1), U-234/U-238, U-235/U-238, and U-236/U-238 can be quantified in 1 mL of urine containing 3% DU with relative precisions (1s) of 10%, 0.4%, and 18%, respectively. For urine containing 75% DU and [U] = 50 ng L-1, the relative precision (1s) of U-236/U-238 is improved to %26lt;3%. At biomonitoring levels ([U] = 5 ng L-1), by increasing the urine volume to 4 mL, U-234/U-238 and U-235/U-238 can be quantified with relative precisions (1s) of 19% and 0.5%, respectively, whereas U-236/U-238 cannot be detected. By further increasing urine volume to 8 mL, comparable levels of isotope ratio precision are possible at [U] as low as 1 ng L-1.
- 出版日期2013
