Determination of fluorescent whitening agents in laundry detergents and surface waters by solid-phase extraction and ion-pair high-performance liquid chromatography

A simple method was developed to detect four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in household laundry detergents and surface waters by ion-pair high-performance liquid chromatography. The FWA concentrations in detergents were measured directly. The contents of FWAs in water samples were extracted by solid-phase extraction (C18-SPE) with ion-pairing reagent, and were then determined by an isocratic ion-pair chromatography (IPC) using a C18 column, applying tetrabutylammonium hydrogensulfate (TBA) as the ion-pairing reagent in mobile phase, and equipped with fluorescence detection. Water samples at various pH conditions for SPE were evaluated. Experimental results indicate that the proposed method is precise and sensitive in analyzing FWAs, and enables quantitation of 0.01-0.1 μg/l in 100 ml water samples. The recovery rates of FWAs in spiked water samples were between 73 and 89%, and the precision (RSD) ranged from 2.6 to 8.9%. Over 7200 μg/g of 4,4′-bis(2-sulfostryl)-biphenyl (DSBP) and 2320 μg/g of 4,4′-bis[(4-anilino-6-morpholino-1,3,5-triazine-2-yl)-amino]stilbene-2,2′-disulfonate (DAS1) were detected in household laundry detergents. Trace amounts of DSBP were detected in surface water samples ranging from 0.2 to 3.7 μg/l.