Spectrophotometric Determination of Scandium (III) with Eriochrome Cyanine R and Cetylpyridinium Chloride – Application to Waters and Synthetic Alloys*

The detailed investigation of a sensitive and selective spectrophotometric method for the trace amounts of scandium is described. The method is based on the reaction of scandium with eriochrome cyanine R reagent in the presence of cetylpyridinium chloride surfactant at pH 4.1, to form a violet-blue ternary chelate which exhibits maximum absorption at 595nm. Beers law is obeyed over the range 0.1-3.0 g25ml, i.e., 0.004-0.12 ppm, with a molar absorptivity of 1.3105 l.mol-1.cm-1, (r=0.9991), Sandells sensitivity index of 0.45 ng.cm-2, a relative error of 0.0-0.4% and a relative standard deviation of 0.6 to 6.1 %, depending on the concentration level.
The method has been applied successfully to determine, scandium in various samples of water and synthetic alloy.