Abstract: In hydrochloric acid medium, Se (Ⅳ) powerfully catalyzes the oxidation of methylene blue by potassium bromate, causing methylene blue to fade. Based on this, a new catalytic kinetic spectrophotometric method was developed in this study for determining trace Se (Ⅳ). Under given conditions, the linear range for Se (Ⅳ) determination was 0–0.6 μg/50 mL. The limit of detection of the developed method was 3.63×10-10 g/mL. This method allowed the determination of Se (Ⅳ) content in original and infused tea so that the leach rates of Se (Ⅳ) from Tieguanyin, Green tea and Black tea in hot water could be calculated from both measured values as being 24.7%, 25.3% and 22.7%, respectively.

Key words: tea, Se (Ⅳ), leaching rate, catalytic kinetic spectrophotometry