ELSEVIER Journal of Pharmaceutical and Biomedical Anals.sis 15 (1997) 1157 1165 JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS A sensitive method for the determination of uranium in biological samples utilizing kinetic phosphorescence analysis (KPA) Mohsen A. Hedaya *, Harry P. Birkenfeld, Ronald L. Kathren Department (!["Pharmaceutical Sciences and United States Transuranium aml Uranium Registries. College ~![ Pharmacy, Wegner Hall, Room 309, Washington State University, Pullman, WA 99164-6510, USA Received 22 April 1996; accepted 23 September 1996 Abstract Kinetic phosphorescence analysis is a technique that provides rapid, precise 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 of the luminescence decay profile and the linearity of the log luminescence 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 excitanon, is proportional to the uranium concentration in the sample. Calibration standards of known uranium concentrauons are used to construct the calibration curve between the initial luminescence intensity and uranium concentrauon. This calibration curve is used to determine the uranium concentration of unknown samples from their initial luminescence intensity. We developed the sample preparation method that allows the determination of uranium concentrations in urine, plasma, kidney, liver, bone spleen and soft tissue samples. Tissue samples are subjected to dry-ashing m a muffle furnace at 600°C and wet-ashing with concentrated nitric acid and hydrogen peroxide twice to destroy the organic component in the sample that may interfere 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 between 0.05 lag 1 ~ and 1000 lag 1 1 (0.05 1000 ppb). The developed sample 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 quantify uranium in different tissue samples obtained over a period of 90 days following a single intraperitoneal uranium dose of 0.1 mg kg ~ in rats. ~ 1997 Elsevier Science B.V. Keywords: Uranium analysis; Kinetic phosphorescence analysis: Assay validation: Uranium biodistribution 1. Introduction * Corresponding author. Tel.: + 1 509 3555622; fax + 1 509 Determination of uranium in biological and 3350162: e-mail: Hedaya@mail.wsu.edu environmental samples is necessary to assess occu- 0731-7085/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII $0731-708 5(96)01 957-7