5-Chlorosalicylic acid spectrophotometric method for the determination of titanium and simultaneous determination of titanium(IV) oxide and iron(III) oxide content of portland cement

Abstract

A spectrophotometric study of the titanium(IV)–5-chlorosalicylic acid (CSA) reaction was carried out to ascertain the suitability of the titanium–CSA complex formed at pH 2.5–3 for the direct spectrophotometric determination of titanium. The method is simple and rapid and possesses reasonable selectivity. A linear calibration graph is obtained up to a concentration of 5.8 µg ml^–1 of titanium. The optimum range for determination (Ringbom) is between 0.53 and 4.8 µg ml^–1. The molar absorptivity and Sandell's sensitivity are 1.9 × 10⁴ l mol^–1 cm^–1 and 1.25 × 10^–3µg cm^–2, respectively, at 355 nm. Application of the method to the simultaneous determination of TiO₂ and Fe₂O₃ in Portland cement was investigated. The absorbance at 510 nm, due to the iron(III)–CSA complex, is recommended for the determination of Fe₂O₃ in cement, whereas the characteristic absorption of the titanium complex at 355 nm is corrected for iron(III) present in the sample. The analysis of cement materials containing different proportions of titanium and iron is feasible over the concentration ranges 1.28–4.8 µg ml^–1 Ti and 18.5–40.2 µg ml^–1 Fe³⁺. The limits of detection (at the 95% confidence level) of the method are 12 and 36 ng ml^–1 for titanium and iron, respectively. The individual determination of titanium in cement samples can also be achieved if iron(III) present in solution is masked by the addition of 0.01 mol l^–1 ascorbic acid. The developed procedure was tested by analysing several samples and was found to give satisfactory results.