Determination of trace titanium (IV) by catalytic kinetic spectrophotometry in brilliant green-cetyl trimethyl ammonium bromide system

Trace titanium (IV) had significant catalytical action on the fading reaction of brilliant green oxidized by hydrogen peroxide in the presence of cetyl trimethyl ammonium bromide in H₂SO₄ medium at 90°C. On the basis of this fact, a catalytic kinetic spectrophotometric determination method of trace titanium was proposed. The optimized experimental conditions were studied. At 625 nm, the absorbance difference (ΔA) between non-catalytic system (A₀) and catalytic system (A) showed good linear relationship with the mass concentration (ρ) of titanium (IV) in the range of 0.021-0.08 μg/mL, with detection limit of 7.87 × 10^-10 g/mL. This catalytic reaction was found as the first order reaction for titanium (IV), and the total reaction was pseudo first order reaction. The apparent reaction rate constant was 5.70 × 10^-4/s, and the apparent activation energy E_a=45.52 kJ/mol. The proposed method had been applied to the determination of titanium (IV) in two steelmaking sinter ore samples, and the results were consistent with the reference values. The relative standard deviations (RSD) were 2.4% and 2.0%, respectively. The recoveries of standard addition were in the range of 98%-102%.