A simple, rapid, effective and eco-friendly decomposition method is developed for the determination of uranium (U) by laser
induced fluorimetry (LIF). The salts of sodium di-hydrogen phosphate (NaH2PO4) and di-sodium hydrogen phosphate (Na2HPO4) were used in the ratio of 1:1 (phosphate flux) for the decomposition and dissolution of refractory, non silicate minerals
like ilmenite, rutile, columbite, tantalite, and xenotime. The effect of associated matrix elements (Ti, Fe, Nb, Ta, Mn and
Y present in the sample) on quenching of uranyl fluorescence was studied. The flux used for the sample decomposition has several
advantages. In the reported sample decomposition methods, α-hydroxy acids are used as complexing agents to prevent hydrolysis
and to get clear and stable solution. This solution can not be directly used for U determination by LIF as α-hydroxy acids
quench uranyl fluorescence, hence separation is required. In the present method no such separation is required. The flux itself
acts as fluorescence enhancing reagent and buffer (maintaining the optimum pH of 7.1 ± 0.1). The fused melt of the flux mixture,
when disintegrated in water, gives clear and stable solution and has high tolerance for most of inorganic quenchers compared
to reported phosphate buffers. Also just by dilution (due to high sensitivity of LIF), the concentration of quenchers could
be brought down well within the tolerance limit. The accuracy and precision of the method was evaluated by analyzing Certified
Reference Materials (IGS-33 and IGS-34 of Institute of Geological Sciences, UK) and Synthetic Minerals. The accuracy of the
data is further evaluated by comparing with standard decomposition methods. The results are well within the experimental error.
The RSD of the method is ±10% (n = 6) at 10 ppm level for Ilmenite and for other minerals the RSD of the method is ±5% (n = 6) at 50 ppm level. The method is being routinely applied to various refractory samples received from Rare Metal and Rare
Earth Investigations for determination of uranium by laser fluorimetry.