An Improved Rhodamine B Method for the Extraction-spectrophotometric Determination of Antimony ( V )

Abstract

The formation of hexachloroantimonate is a crucial step in the spectrophotometric determination of antimony by the Rhodamine B method. In the proposed method, antimony is quantitatively converted with cerium (IV) to hexachloroantimonate in the presence of the chloride mixture containing 1 moll/ hydrogen ion and 5 mol/l chloride ion and the hexachloroantimonate is directly extracted from aqueous phase to diisopropyl ether. A colored complex of hexa chloroantimonate and Rhodamine B is subsequently formed by shaking organic phase with the aqueous solution of Rhodamine B. Plots of the absorbance at 550 nm against the concentration of antimony follows Beer's law in the region from 0.1 to 1 ppm. At 0.2 ppm antimony level, the relative standard deviation (n =6) is 6.2%. Iron (III) gives litte or no interference with the determination of antimony by the proposed method.