Spectrophotometric flow injection determination of titanium in rocks

Abstract

A flow-injection system for the spectrophotometric determination of titanium in rocks using chromotropic acid as the colour-forming reagent is described. Sample decomposition involving the use of metaborate was investigated. In addition, the optimization of chemical and physical variables and a study of interfering ions was also carried out. Standard rock samples from the United States Geological Survey and Geological Survey of Japan were used to assess the accuracy of the method. With a solution sampling frequency of 80 h^–1, the system yields precise results (relative standard deviation <0.6%), making the determination of 0.1–3.0% TiO₂ in rock samples possible. The proposed system is stable for at least 4 h, has low reagent consumption (about 6 mg per sample) and a detection limit of 0.05 µg cm^–3.