Occurrence of fluorescent whitening agents in sewage and river water determined by solid-phase extraction and high-performance liquid chromatography

Fluorescent whitening agents (FWAs) used in laundry detergents were determined in aqueous samples from sewage treatment plants and rivers using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC)with post-column UV irradiation and fluorescence detection. FWAs were extracted from 10-200-mL water samples with C-18 bonded-phase silica extraction disks and eluted with methanol-containing tetrabutylammonium ion-pairing reagent. No further sample cleanup steps were necessary due to the sensitive and selective fluorescence detection. Recovery of FWAs from raw sewage, primary effluent, secondary effluent, and river water ranged from 76 to 96%. The overall precision of the method, indicated by the relative standard deviation, ranged from 1 to 11%. The limit of quantification was less than 30 ng/L. The concentrations of the two most frequently used FWAs ranged from 7 to 21 mu g/L in primary effluent, from 2.6 to 8.9 mu g/L in secondary effluent, and from 0.04 to 0.57 mu g/L in river water. FWA mass flows calculated from river water concentrations ranged from 0.45 to 1.2 mg day(-1) person(-1). If calculated on the basis of the consumed amount of FWAs, 1.4-5.6% was found in surface water. Light-induced isomerization and liquid-solid partitioning of FWA isomers were studied in samples of raw sewage and primary and secondary effluent. Isomers formed during the exposure to sunlight were found to have lower affinity for the suspended solids in sewage than the parent FWAs.