Spectrophotometric determination of persulfate anion via oxidative depolarization of methyl orange induced by ferrous ions

Abstract

A rapid, simple, and sensitive spectrophotometric method was developed for the determination of persulfate in this study, based on the oxidation decolorization of methyl orange (MO) with sulfate radicals and hydroxyl radicals generated by the conjunction of persulfate with ferrous ions. The depletion of MO at its maximum absorption wavelength (507 nm) is in proportion to the concentration of persulfate in water. There was a good linear relationship (above 99%) between the depletion of MO and the concentration of persulfate in the ranges of 0.5–100 μmol L⁻¹ with a detection limit of 0.17 μmol L⁻¹ under the optimized conditions. The proposed MO method for the determination of persulfate in water was effective to tolerate the interferences of common coexisting foreign species in aqueous solutions. The results were as satisfactory as that obtained by the classical iodometric method used in practical water samples. Additionally, the proposed MO method is rather inexpensive to measure the concentration of persulfate by using standard laboratory instruments (spectrophotometer).

Keywords:

• Spectrophotometric determination
• Oxidative decolorization
• Methyl orange
• Persulfate
• Ferrous ions

Acknowledgments

This research was supported by the Natural Science Foundation of China (grant number 51178134, 51378141), and the National Science and Technology Pillar Program of China (grant number 2012BAC05B02).