Capillary electrophoretic analysis of organic anions in tannery wastewater including high contents of chloride and sulfate

A new sample preparation method for capillary electrophoresis is presented to analyze organic anions in industrial wastewater which is highly contaminated with inorganic salts. Chloride and sulfate can be completely removed by use of strong cation exchangers in their Ag- and Ba-form. Good recoveries were found for 10 small organic acids out of spiked pure water after removal of up to 2 g/L for both, chloride and sulfate. Recoveries of oxalic acid were decreasing from 92 to 47% with increasing salt contents. Using tannery wastewater samples, irreversible adsorption of the organic load onto the cation exchangers could be minimized by an additional washing step. Included in these samples, 17 peaks could be identified by spiking 46 organic and inorganic compounds. The alteration of the organic anions present in the wastewater samples could be characterized along a biological treatment pilot plant. Some of these anions proved to be persistent to biological degradation.