Thin layer chromatographic study of Indian bauxites

Abstract

Thin layer chromatography (TLC) has been used for the detection and separation of Al³⁺, Fe²⁺, Si⁴⁺ and Ti⁴⁺ in bauxite. Thirty bauxite samples of different geological origin have been studied to identify the optimized chromatographic systems capable of selective separations of the constituents. Binary and ternary separations of Al³⁺, Fe²⁺, Ti⁴⁺ and Si⁴⁺ in bauxite were realized with chromatographic systems comprising various combinations of silica gel G, silica gel H and microcrystalline cellulose coated plates and aqueous mobile phases consisting alkali salt solutions, formic acid and hydrochloric acid etc. The chromatographic system consisting of silica gel H and mixture of 10% aqueous solutions of sodium chloride and formic acid in 8:2 (v/v) ratio was found to be the ideal combination for the analogous separation of Al³⁺, Fe²⁺ and Ti⁴⁺ in bauxites. The efficacy of optimized chromatographic system has been investigated by monitoring reproducibility of RF values and spot compactness with respect to change in bauxite geology, sample concentration and change of mobile phase composition. Chromatograms of the cations were quantitatively evaluated by scanning densitometry in comparison with wet analysis method.