DETERMINATION OF THORIUM AND URANIUM IN URINE WITH INDUCTIVELY-COUPLED ARGON PLASMA-MASS SPECTROMETRY

An accurate and simple method has been developed for the determination of thorium and uranium in urine using inductively coupled argon plasm a mass spectrometry (ICP-MS). Determination of thorium and uranium was by; external calibration using matrix matched standards and high-puri ty spiking materials. Aliquots of each urine specimen were diluted (19) with 0.2 mol l(-1) nitric acid containing iridium as an internal st andard. The counts at mit 232 (thorium), 238 (uranium) and 193 (iridiu m) were measured, and ratios of the counts at m/z 232 or 238 to those at m/z 193 were calculated. These ratios were compared with those from urine-based calibration standards to calculate the thorium and uraniu m concentrations in unknown specimens. The concentrations of thorium a nd uranium were calculated as mu g l(-1) in the sample and also correc ted for dilution via creatinine measurement, expressed as mu g g(-1) o f creatinine. The method has-been evaluated by determination-of refere nce materials from the Los Alamos National Laboratory, as well as of t hose from the Oak Ridge National Laboratory. The proposed method provi des the basis of an accurate method for determining thorium and uraniu m in unexposed;subjects as well: as in:those considered to be exposed to thorium or uranium through environmental or other pathways. About 4 0 specimens, excluding blanks, calibration standards and quality-contr ol materials, can be processed in an 8 h day.