Determination of Hydrogen Peroxide in Disinfectant by Spectrophotometry Based on Color Reaction of Sodium Diphenylaminesulfonate Catalyzed by Fe³⁺

The disinfectant sample (1.00 mL) was diluted to 100 mL with distilled water. 5.00 mL of the solution was mixed with 5.0 mL of 8.0 g·L^-1 sodium diphenylaminesulfonate solution, and 2 mL of 3 mol·L^-1 H₂SO₄ solution, 0.5 mL of 0.1 mol·L^-1 FeCl₃ solution were added. The volume of the solution was made up to 50.0 mL with distilled water. After reaction at room temperature for 60 min, the absorbance was measured at the wavelength of 410 nm using a 1 cm cuvette with the reagent blank as a reference. The results showed that linear relationship was found between the absorbance of the solution and the concentration of hydrogen peroxide in the range of 0.116-1.16 mmol·L^-1. The detection limit (3s/k) was 0.02 mmol·L^-1 and the apparent molar absorptivity was 1.34×10³L·mol^-1·cm^-1. The proposed method was applied to determination of content of hydrogen peroxide in disinfectant, giving the measured value consistent with the labeled value and the determination result obtained by the iodometric method. The relative standard deviations (n=6) of the measured values were less than 2.0%.