Bromophenol blue

Bromophenol blue is an acid phthalein dye, and it is used as a tracking dye for electrophoresis. Bromophenol blue is also used as a pH indicator, with a transition range of pH 3 to 4.6. Bromophenol blue is used as a sensor for the determination of several compounds including ammonia, drugs, proteins and amino acids. The binding of Bromophenol blue to proteins is accompanied by the appearance of a strong absorbance at 610 nm^[1][2]. In Vitro:Preparation of Bromophenol blue Staining Solution:^[2]
The Bromophenol blue (0.0075%) was dissolved in a solution containing 15 mL of 95% ethanol, 2.5 mL of glacial acetic acid and brought to a final volume of 100 mL with distilled water. The Bromophenol blue-ethanol-glacial acetic acid solution was stable at least for 1 week.
Protein assay:^[2]
Proteins were dissolved in distilled water, and their concentrations were adjusted to 1 mg/mL with the exceptions of the myoglobin solution which was prepared gravimetrically, and the y-globulin solution, which was made according to the suppliers. For performing the protein assay, protein solutions containing from 10 to 80 μg of protein in 0.1 mL were mixed with 0.9 mL of the Bromophenol blue solution. The absorbance at 610 nm was determined using a blank made by mixing 0.1 mL of distilled water and 0.9 mL of the dye solution.