Analysis of sulphonated azodyes and their degradation products in aqueous solutions treated with a new electrochemical method

Aqueous solutions of four sulphonated azodyes, Reactive Orange 91, Reactive Red 184, Reactive Blue 182 and Reactive Black 5, containing 0.2 mol/L of electrolyte were treated in a laboratory scale electrolytic cell with a new electrochemical method intended for the textile wastewater treatment. The electrochemical process was monitored by means of absorbance of UV-Vis light and chemical oxygen demand values. Carbon fleece was used as a cathode, and platinated titanium was used as an anode. Reversed-phase high-performance liquid chromatography coupled with photodiode array and mass spectrometric detectors was applied for the analysis of dyes, their impurities and degradation products after the electrochemical treatment. Dihexylammonium and triethylammonium acetate as ion-pairing reagents, or alternatively ammonium acetate as an ion-exclusion suppressing reagent, were used to improve the separation.