Determination of detergent-derived fluorescent whitening agent isomers in lake sediments and surface waters by liquid...

A method for the quantitative determination of three different fluorescent whitening agents (FWAs) in lake sediments and surface waters is described. Stereoisomers of the two main laundry detergent FWAs of the diaminostilbene type (DAS 1) and of the distyrylbiphenyl type (DSBP), as well as total BLS (a compound contained in detergents until a few years ago), were quantitated in sediments and water from Greifensee, a small lake in Switzerland. The freeze-dried sediments were extracted in an ultrasonic bath using methanol with tetrabutylammonium hydrogen sulfate as an ion-pairing reagent. Aqueous samples were extracted with C18 extraction disks, which were subsequently eluted by methanol with tetrabutylammonium hydrogen sulfate. Both extracts from solid and aqueous samples were analyzed by reversed-phase high-performance liquid chromatography. Fluorescence detection was applied after postcolumn UV irradiation. Analytical reproducibility ranged from 1 to 12% (relative standard deviation). Limits of quantitation were 1-11 μg/kg of dry matter and 0.2-3 ng/L for solid and aqueous samples, respectively. Recoveries ranged from 93 to 100% and from 87 to 95% in solid and aqueous samples, respectively. Concentrations of DAS 1 and DSBP ranged from 0.4 to 1.4 mg/kg of dry matter in top sediment layers and from 12 to 98 ng/L in lake water. Concentrations of BLS were between 0.02 and 0.08 mg/kg of dry matter in top sediment layers and <0.2 ng/L in lake water.