Determination of 236U/ 238U and 235U/ 238U isotope ratios in human urine by inductively coupled plasma mass spectrometry

Patrick J. Gray, Lingsu Zhang, Hanna Xu, Melissa McDiarmid, Katherine Squibb, José A. Centeno

Research output: Contribution to journalArticle

Abstract

Isotopic ratios of urinary uranium (U) provide a decisive tool in diagnosing a patient's potential exposure to depleted uranium (DU). This study investigated the measurement of urinary 236U/ 238U and 235U/ 238U ratios of ultra trace concentrations using a sector field inductively coupled plasma mass spectrometer (ICP-MS). Uranium was separated from the urinary matrix and pre-concentrated by co-precipitation with calcium and magnesium after addition of ammonium hydroxide. The precipitates were collected, dissolved and analyzed by ICP-MS. 235U/ 238U and 236U/ 238U ratios were measured using a desolvating sample introduction system and a sector field ICP-MS. These ratios were accurately measured in samples containing as low as 5ngL -1 U. 236U measurement was hindered by abundance sensitivity limitations and uranium hydride ( 235UH) formation. Measured 235U/ 238U and 236U/ 238U ratios were about 7×10 -3 and -6, respectively, in urine samples from patients not exposed to DU. The 235U/ 238U ratio was consistently about 2×10 -3 in 12 urine samples from patients with embedded fragments of DU, while the corresponding ratio of 236U/ 238U ranged from 9×10 -6 to 33×10 -6. This wide range in 236U/ 238U ratios might suggest different sources of depleted uranium in those DU-urine samples. It is proposed that 235U/ 238U and 236U/ 238U ratios are 7×10 -3 and -6, respectively, in urine samples from individuals not exposed to DU, and 2×10 -3 and >7×10 -6, respectively, in urine samples from DU-exposed individuals.

Original languageEnglish (US)
Pages (from-to)94-100
Number of pages7
JournalMicrochemical Journal
Volume105
DOIs
StatePublished - Nov 2012
Externally publishedYes

Keywords

  • Depleted uranium
  • Inductively coupled plasma mass spectrometry
  • Uranium
  • Uranium isotope ratio
  • Urine

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy

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