Determining picogram quantities of uranium in urine by isotope dilution inductively coupled plasma mass spectrometry. Comparison with alpha-spectrometry

An accurate and simple method has been developed for the determination of u ranium in urine using inductively coupled plasma mass spectrometry (ICP-MS) . Isotope dilution analysis was applied using the long-lived uranium nuclid e U-233 as a spike in 1.3-fold diluted urine samples. To avoid matrix effec ts and salt depositions in the interface region of the instrument a prototy pe concentric-flow nebulizer with a mini cyclonic spray chamber was used at a reduced sample uptake rate of 0.3 ml min(-1). The method was evaluated b y comparison with alpha -spectrometry, as well as by analysis of National I nstitute of Standards and Technology (NIST) Standard Reference Material (SR M) 2670, Toxic Metals in Freeze Dried Urine, for which published results of isotope dilution thermal ionization mass spectrometry (TIMS) and radiochem ical neutron activation analysis (RNAA) measurements are available. ICP-MS and alpha -spectrometry yielded consistent results (Wilcoxon, p = 0.87). Th e ICP-MS mean value (+/-95% confidence interval) of 143 +/- 10 pg ml(-1) ob tained for the SRM 2670 agreed with the reported RNAA value of 130 +/- 18 p g ml(-1) at the 95% confidence interval; however, they exceeded the reporte d TIMS value of 113 +/- 3 pg ml(-1). The proposed method provides a means f or determining uranium in unexposed subjects as well as in those considered to be exposed. Potential exposure to uranium amongst employees of UNHCR in western Kosovo was assessed.