Application of a differential technique in laser-induced fluorimetry: simple and a precise method for the direct determination of uranium in mineralised rocks at the percentage level

A simple, rapid, cost-effective, accurate and precise differential laser-induced fluorimetric method for the direct determination of uranium in mineralised rocks at the percentage level is presented, based on the comparison of the fluorescence of the standard with a sample of similar but unknown concentration on the same sample weight basis, by the use of H3PO4NH4H2PO4 as a fluorescence enhancing reagent. The relative standard deviation of the method was 0.3-0.5% (n=9) for 0.04 and 3.4% U3O8. The proposed technique is suitable for the determination of uranium in samples containing >0.01% uranium. The method has been evaluated using standards, SY-2, SY-3, low grade uranium ore-IAEA reference samples and core samples of diverse matrices. The results are in good agreement with the published data and those obtained by conventional fluorimetry and other methods and are of comparable precision to those obtained by titrimetric assay.