Rapid determination of monopersulfate with bromide ion-catalyzed oxidation of 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS)

A sensitive spectrophotometric method (the Br − -ABTS method) for measuring monopersulfate (PMS) of 0–20 μM in water was established. The Br − -ABTS method was based on the oxidation coloration reaction where Br − as catalyst promoted PMS for oxidation of ABTS forming the green-colored ABTS radical (ABTS • + ) under pH 3.0 (50 mM phosphate buffer). ABTS • + could be quantitatively measured at 415 nm, 650 nm, 732 nm and 820 nm using UV–vis spectrophotometer. There was a well linear relationship between the absorbance of ABTS • + and PMS concentration with the value of R 2 being 0.999. The proposed Br − -ABTS method was highly sensitive, and the absorbance generated by Br − -ABTS at 415 nm was 6.59 × 10 4 cm −1 per M (mol L –1 ) of PMS. The changes of pH from 3.0 to 9.0 had an insignificant effect on the calibration curve of Br − -ABTS method. The reaction of PMS with ABTS had a stoichiometric coefficient of 1:1.96 at the pH 3.0. The residual absorbance of ABTS •+ in ultrapure water, Xiangjiang water and Hou-lake water was stable within 30 min. Moreover, the trace PMS concentration of 0.03–20 μM in ultrapure water, 0.05–20 μM in natural water (e. g. Xiangjiang water and Hou-lake water) and 1–20 μM in wastewater was accurately measured with the proposed Br − -ABTS method. Additionally, the interference of natural water matrix (e. g. humic acid), metal ions (e. g. Co(II), Fe(III) and Cu(II)) and hydroxylamine had barely interference for the proposed Br − -ABTS method. Furthermore, the Br − -ABTS method was more accurate and flexible to determine PMS concentration than DPD method during the decolorization of rhodamine B in the Co(II)/PMS system, Cu(II)/PMS system and hydroxylamine/Fe(III)/PMS process.