Rapid and selective spectrophotometric determination of peracetic acid in water via oxidative coloration of N,N-diethyl-p-phenylenediamine with the assistance of Co(II)

Peracetic acid (PAA) has garnered considerable interest due to its exceptional disinfection properties and strong oxidizing capabilities. However, the coexistent hydrogen peroxide (H 2 O 2 ) in the PAA solution, which has similar chemical characteristics with PAA, makes accurate measurement of PAA concentration challenging. In this study, a rapid, sensitive, and reliable spectrophotometric method for determining PAA was developed. The method involves the oxidation of N , N -diethyl- p -phenylenediamine (DPD) by Co(II)-catalyzed PAA, resulting in the formation of a stable pink DPD radical (DPD ●+ ). It is worth noting that Co(Ⅱ) is an excellent PAA catalyst but is inactive with H 2 O 2 . Consequently, there is minimal interference from the coexistent H 2 O 2 in the determination of PAA. The absorbance of DPD ●+ at 551 nm was well linear (R 2 > 0.999) with concentrations of PAA in the range of 0–80 μM under optimized reaction conditions, and the limit of detection was determined to be low as 0.175 μM. Furthermore, the proposed Co(II)-DPD spectrophotometric method demonstrates strong resistance to common natural water constituents (ferric ions, sulphate ions, nitrate ions, chloride ions, bicarbonate ions, and humic acid) and is suitable for the accurate determination of PAA in natural water sources like groundwater and surface water. Additionally, the proposed Co(II)-DPD spectrophotometric method was dependable for quantifying PAA concentrations and monitoring PAA changes in Co(II)/PAA, Cu(II)/PAA, Fe(II)/PAA, and hydroxylamine/Fe(II)/PAA processes. In conclusion, the proposed Co(II)-DPD spectrophotometric method can be utilized as an alternative method for the rapid and accurate determination of PAA in water.