A Simple and Selective Spectrophotometric Method for the Determination of Uranium at Nano-trace Levels in Some Real, Environmental, Biological Food and Soil Samples Using 2-hydroxynaphthaldehydebenzoylhydrazone

A new spectrophotometric reagent 2-hydroxynaphthaldehydebenzoylhydrazone (HNABH) has been synthesized and characterized. A very simple, ultra-sensitive and highly selective non-extractive new spectrophotometric method for the determination of ultra-trace amount of uranium using 2-hydroxynaphthaldehydebenzoylhydrazone (HNABH) has been developed. HNABH undergoes reaction in a slightly acidic solution (0.00025-0.00075M H2S04) with uranium to give a very light yellow chelate, which has an absorption maximum at 406-nm. The reaction is instantaneous and absorbance remains stable for over 24h. The average molar absorption coefficient and Sandal’s sensitivity are found to be 2.87×105 L mol-1cm -1and 8-ng cm-2 of, U respectively. Linear calibration graphs were obtained for 0.01- 60-mg L-1 of U having detection limit of 1.0-µg L-1 and RSD 0 – 3.0 %. The stoichiometric composition of the chelate is 1:1 (UVI: HNABH). A large excess of over 60 cations, anions and some common complexing agents (such as chloride, azide, tartrate, EDTA, SCN- etc.) do not interfere in the determination. The method was successfully used in the determination of uranium in several Certified Reference Materials (alloys, steels, ores, standard uranium solution water and marine sediment) as well as in some environmental waters (potable and polluted), biological samples (human blood, urine, milk, hair and nails), soil and oil samples, and complex synthetic mixtures. The results of the proposed method for assessing biological, food, water and vegetables samples were found to be in excellent agreement with those obtained by ICP-OES and AAS, respectively. The method has high precision and accuracy (s =± 0.01 for 0.5 mg L-1).