A SENSITIVE METHOD FOR THE DETERMINATION OF URANIUM IN BIOLOGICAL SAMPLES UTILIZING KINETIC PHOSPHORESCENCE ANALYSIS (KPA)

Kinetic phosphorescence analysis is a technique that provides rapid, p recise and accurate determination of uranium concentration in aqueous solutions. This technique utilizes a laser source to excite an aqueous solution of uranium, and measures the emission luminescence intensity over time to determine the luminescence decay profile. The lifetime o f the luminescence decay profile and the linearity of the log luminesc ence intensity versus time profile are indications of the specificity of the technique for uranium determination. The luminescence intensity at the onset of decay (the initial luminescence intensity), which is the luminescence intensity at time zero after termination of the laser pulse used for excitation, is proportional to the uranium concentrati on in the sample. Calibration standards of known uranium concentration s are used to construct the calibration curve between the initial lumi nescence intensity and uranium concentration. This calibration curve i s used to determine the uranium concentration of unknown samples from their initial luminescence intensity. We developed the sample preparat ion method that allows the determination of uranium concentrations in urine, plasma, kidney, liver, bone spleen and soft tissue samples. Tis sue samples are subjected to dry-ashing in a muffle furnace at 600 deg rees C and wet-ashing with concentrated nitric acid and hydrogen perox ide twice to destroy the organic component in the sample that may inte rfere with uranium determination by KPA. Samples are then solubilized in 0.82 M nitric acid prior to analysis by KPA. The assay calibration curves are linear and cover the range of uranium concentrations betwee n 0.05 mu g l(-1) and 1000 mu g l(-1) (0.05-1000 ppb). The developed s ample preparation procedures coupled with the KPA technique provide a specific, sensitive, precise and accurate method for the determination of uranium concentration in tissue samples. This method was used to q uantify uranium in different tissue samples obtained over a period of 90 days following a single intraperitoneal uranium dose of 0.1 mg kg(- 1) in rats. (C) 1997 Elsevier Science B.V.