Bleed fastness of fluorescent whitening agents in mass whitened paper.
Paper samples mass whitened with fluorescent whiteing agents (FWAs) of three different types (di-, tetra-, and hexasulfonated derivatives of 4,4'-diaminostilbene-2,2'-disulfonic acid) were examined for bleed fastness in five different eluents. Fluorescece intensity was measured by a sensitive spectrofluorimetric technique instead of the usual visual assessment. The degree of bleed obtained from each of the FWAs tested was less than 0.4mg/600 cm2 of paper surface area. The FWAs were applied at a normal concentration of use i.e. 0.05% active substance. FWAs with a high degree of sulfonation tend to bleed in aqueous solvents, and those with a lower degree of sulfonation in alcohol solutions. In aqueous acid solutions the degree of bleed was very low in all cases (0.04 mg/600 cm2 of paper surface area). In fatty solutions there was no bleed at all. The limit of detection was 3mug/600 cm2 of paper surface area, with an accuracy of +/-15%.
D004396:Coloring Agents / Q000032:analysis*; D005470:Fluorometry; D008722:Methods; D010209:Paper / Q000032:analysis*; D010782:Photolysis; D012995:Solubility; D013267:Stilbenes / Q000032:analysis; D013451:Sulfonic Acids / Q000032:analysis
D004396:Coloring Agents; D013267:Stilbenes; D013451:Sulfonic Acids