Capillary electrophoresis was used for determining Belofors, which are used as optical bleaching agents for improving the whiteness of writing paper. Sodium dodecyl sulfate (SDS) was used as a modifier of capillary walls in the separation of water-soluble Belofors. An optimum buffer electrolyte for separating and determining Belofors was as follows: 0.5 mM sodium hydrogen phosphate, 12.2 mM sodium tetraborate, and 30 mM SDS; pH 9.1. Bleaching agents in 39 samples of paper manufactured in Russia, Finland, Sweden, France, the Czech Republic, and Austria were determined and characterized. Common features for classifying paper types in accordance with brands and manufacturers were found. [ABSTRACT FROM AUTHOR]