Simultaneous spectrophotometric determination of peracetic acid and the coexistent hydrogen peroxide using potassium iodide as the indicator

Abstract

Recently, increasing attention has been paid for using commercial peracetic acid (PAA) solution as an efficient disinfectant or a strong oxidant in water treatment. Simultaneous determination of PAA and hydrogen peroxide (H₂O₂) is vital because PAA solution is commonly available as a mixed solution containing the peroxides PAA and H₂O₂. In this study, a simple, rapid and reliable spectrophotometric method for the simultaneous determination of PAA and H₂O₂ was developed. This method was based on the rapid oxidation of excess potassium iodide by PAA and H₂O₂ in the presence of ammonium molybdate to yield yellow-colored triiodide ions (I₃⁻) that could be quantitatively measured using an UV-Vis spectrophotometer. The absorption of generated I₃⁻ at 350 nm increased linearly (R² > 0.999) with the concentrations of total peroxides and PAA in the range of 0–70 μM. The sensitivities were respectively measured to be as high as 2.596 × 10⁴ M⁻¹ cm⁻¹ for total peroxides and 2.616 × 10⁴ M⁻¹ cm⁻¹ for PAA, while the corresponding limits of detection were calculated to be as low as 0.19 μM and 0.18 μM. The concentration of the H₂O₂ coexisting in PAA solution was obtained by subtracting the concentration of PAA from the concentration of total peroxides. The concentrations of total peroxides, PAA and H₂O₂ in practical water samples measured with this proposed method were in good agreement with the values measured with the earlier reported spectrophotometric method using N,N-diethyl-p-phenylenediamine as the indicator. Therefore, this proposed spectrophotometric method could be considered as an alternative method for the simultaneous determination of PAA and H₂O₂ coexisting in PAA solution.