Spectrophotometric study of reactions of scandium, ytrium and lanthanum ions with some triphenylmethane dyes in the presence of cationic surfactants

Abstract

Optimum conditions for the formation of ternary complexes of scandium, ytrium and lanthanum ions with chrome azurol S, eriochrome cyanine R and pyrocatechol violet in the presence of cetyltrimethylammonium, cetypyridinium and tetradecyldimethylbenzyl-ammonium (zephiramine) ions are described. The spectrophotometric determination of scandium with chrome azurol S and zephiramine exhibits the greatest sensitivity (ϵ = 1.50 × 10 5 l mol −1 cm −1 at 610 nm). In the spectrophotometric determination of scandium with eriochrome cyanine R and cetylpyridinium ion (ϵ = 9.2 × 10 4 at 600 nm), the interference caused by yttrium is the least. In the best method for yttrium (with pyrocatechol violet and zephiramine), the molar absorptivity is 3.3 × 10 4 at 660 nm. Lanthanum does not form ternary complexes of analytical interest in these systems. Some aspects of the formation of ternary complexes with cationic surfactants are discussed.