Typical filter paper used in chemistry lab (e.g. Whatman #1) exhibits autofluorescence in near UV with excitation maximum at 365 nm and emission maximum at 440 nm. It was reported in literature1 that fluorophores from filter paper can be extracted by PBS buffer in wide range of pH, and thus they are at least partially soluble in water. However, cellulose, the major component of filter paper, is not fluorescent in this wavelengths range and is insoluble.
What is the source of filter paper fluorescence? I assume it comes from paper pretreatment and bleaching, but what is chemical identity of fluorescent compounds in it?