Direct Spectrophotometric Determination of Uranium in Industrial Grade Phosphoric Acid and Phosphorites without its Prior Separation using Arsenazo III Dye

*Hisham kadry Fouad, Randa Maged El-Rakaiby and Abdo Ali Abdo

Analytical Chemistry Department, Nuclear Materials Authority, P.O box 530 Maadi, Cairo, Egypt

Corresponding author; Tel.; +201223320504; Fax; 202-27585831

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Summary: A developed, direct, rapid and sensitive spectrophotometric determination of uranium in Egyptian industrial grade phosphoric acid and phosphorites using arsenazo III as a chromogenic dye was proposed in the present article. The determination was performed without prior separation either by solvent extraction or ion exchange of uranium from its matrix. The basis of the developed method was to overcome the interference effect using masking agents without prior separation of uranium by either technique during the direct determination of uranium using arsenazo III dye. The formed 1:1  U - Arsenazo III complex was stable for 20 minutes. The severe interference due to phosphate anion (39.5 % in H3PO4 and about 25 % in phosphorites) was treated by using 10 % ammonium molybdate, where calcium (47 % in phosphorites and 4 % in H3PO4) and iron (about 1.5 % in phosphorites and H3PO4) were masked using 10 % EDTA - 2Na. The other accompanying elements show no interference effect. Beer's law was obeyed in the range from 0.2 to 3 µg/mL with molar absorptivity ε = 0.56 x 103 L. mol-1 cm-1 and an average standard deviation of 0.36. The R.S.D for 10 replicate measurements of 50 µg/mL was 0.51 %.  

Sabrein Ibrahim,
Oct 12, 2016, 2:14 PM