Spectrophotometric determination of uranium with arsenazo-III in the presence of N-cetyl-N,N,N-tri-methylammonium bromide as surfactant

摘要

A simple, sensitive and efficient spectrophotometric method is proposed for rapid determination of uranium using arsenazo-III in perchloric acid. The reaction between arsenazo-III and U(VI) was instantaneous in 3 mol L ~(-1) HClO_4. N-cetyl-N,N,N-trimethylammonium bromide was used for increasing the sensitivity and selectivity of the complex. The absorbance remains stable for over 48 h in the presence of surfactant. The method allows the determination of uranium in the range of 1-20 μg g~(-1) with a molar absorptivity of 3.9 × 10~5 dm~3 mol~(-1) cm~(-1) at 681 nm. Sandell's sensitivity of the complex was calculated to be 6.4 ng cm~(-2) at λ_(max) 681 nm. A significant enhancement was achieved in the sensitivity of the proposed method whereas, Relative Standard Deviation was reduced from 4.5 to 1.7% in the presence of surfactant. Among various diverse ions studied, fluoride, cyanide, citrate, sulfate and phosphate interfere beyond the tolerance limit. Among cations only Cr~(3+) and Co~(2+) decreased the normal absorbance. The validity of the reported method was tested by determining uranium in the environmental water samples and Standard Reference Material. The results agreed closely with the reported values. The proposed method is new, easy in operation and better in sensitivity than many of the existing methods.