Serious interference of dissolved organic compounds in the laser induced fluorimetric determination of uranium in water: a selective & sensitive method for the laser induced fluorimetric determination of uranium in water
In this report, serious negative interference of Dissolved Organic Compounds (DOCs) in the laser/LED fluorimetric determination of uranium in natural and waste waters has been amply demonstrated. The experiments exploring the effects of the concentration of individual DOCs on the fluorescence intensity of a fixed concentration of uranium(VI) were designed involving about 15 different DOCs, mostly being the degradation products of humic acid and lignin, and the corresponding results obtained were compared with the results obtained by applying the method to a host of (about 500) real natural water samples sampled from areas of diverse geological and environmental settings. The results were compared with those obtained by other standard methods. In most cases, the fluorescence signal increases substantially on destruction of the DOCs present in the water samples studied, depending on the contents of the DOCs and their respective complexing abilities. Woefully, determination of low contents of uranium in some of the natural water samples by the hitherto recommended/prescribed LIF or LED fluorimetric methods often entails a great deal of difficulty in the interpretation of analytical results obtained, in spite of the metal ion (uranium) being actually present in them in significant quantities. Based on the above study, an improved LIF/LED fluorimetric method has been developed, which is robust and highly effective for accurate and precise determination of uranium(VI) in any type of water sample.