Naphthol blue black (NBB) has been used to stain soluble proteins.
Naphthol blue black (NBB) is an textile diazo dye, with high photo- and thermal-stability. Photoelectrochemical degradation of this dye yields colorless quinone as end product. Pure grade of NBB is generally used for dyeing foodstuffs, drugs and cosmetics. It is also used as a protein stain in chromatography and electrophoresis and as a biological stain. Commercial grade of NBB is a widely used textile dye. It is used in dyeing wool, nylon, silk and in textile printing. In addition, it is also employed for coloring of soaps, anodized aluminum and casein, wood stains and writing ink preparation.