DETERMINATION OF BENZENESULFONATES AND NAPHTHALENESULFONATES IN WASTE-WATER BY SOLID-PHASE EXTRACTION WITH GRAPHITIZED CARBON-BLACK AND ION-PAIR LIQUID-CHROMATOGRAPHY WITH UV DETECTION

Highly water-soluble benzene- and naphthalenesulfonates are widely used in chemical, pharmaceutical, and textile industries, This paper presents a solid-phase extraction method for the enrichment of aromatic sulfonates from industrial wastewaters. A graphitized carbon black (Carbopack B) with positively charged oxonium groups was used as an adsorbent. The graphite structure and anion exchange sites make Carbopack B a very selective adsorbent for aromatic anions. Desorption of sulfonates was achieved with 50 mM ammonium acetate in methanol/ dichloromethane. Reversed-phase ion-pair liquid chromatography with diode array detection was used for separation and quantification. With the exception of some amino-substituted compounds, recoveries were generally >90% with relative standard deviations of 0.2-5.0% for replicate analyses. The detection limits for 100 mL samples were between 0.1 and 1.0 mu g/L. Higher molecular compounds, especially humic substances, were almost absent in the final extracts, which is helpful for analyses of environmental samples. Twelve aromatic sulfonates were identified and quantitatively determined by applying this method to wastewater from a textile manufacturing plant. 3-Nitrobenzenesulfonate was found as a major pollutant in concentrations of up to 5 mg/L.