Bromophenol Blue Solution CAS 115-39-9

It is a classic acid-base indicator in the laboratory, with a color change range of pH 2.8 (yellow) to 4.6 (blue), and the intermediate transition stage may appear green or blue purple. This characteristic makes it an important tool for determining the endpoint in acid-base titration experiments. For example, in the titration process of strong acid and weak base, bromophenol blue can accurately indicate the stoichiometric point through color transition (yellow → blue), avoiding errors caused by excessive titration. In addition, its sodium salt form (dissolved in water and appearing blue) can serve as an adsorption indicator in non-aqueous titration, achieving endpoint detection by forming complexes with metal ions.

The application in the field of biochemistry focuses on gel electrophoresis technology, and its core functions include:
Electrophoretic migration tracing: as a small molecule dye (molecular weight 669.96), the migration speed in polyacrylamide gel or agarose gel is similar to that of small molecule nucleic acid (such as primer, siRNA) or protein (such as peptide segment). By adding bromophenol blue to the sample, the electrophoresis progress can be monitored in real time to prevent the target molecules from running out of the gel range. For example, in SDS-PAGE experiments, 0.1% bromophenol blue solution is commonly used to label the migration front of protein samples.
Nucleic acid and protein staining: it can combine with nucleic acid (DNA/RNA) to form a blue complex for staining observation after gel electrophoresis. Its sodium salt form is more soluble in water and can be directly prepared as a staining solution, simplifying the experimental process.

The application in environmental science mainly involves water quality analysis and heavy metal pollution monitoring:
Rapid pH detection: By preparing bromophenol blue indicator solution (such as 0.1% ethanol solution), the acidity and alkalinity of water can be detected on site. For example, in industrial wastewater treatment, it is possible to quickly determine whether the wastewater meets the discharge standards (pH 6-9).
Extraction and Separation of Heavy Metal Ions: Complex compounds formed with metal ions such as copper, zinc, and cobalt can be extracted by organic solvents (such as chloroform and benzene) and quantitatively analyzed for heavy metals using spectrophotometry. Research has shown that under pH 5-6 conditions, the extraction rate of bromophenol blue for Cu ² ⁺ can reach over 99%, with a detection limit as low as 0.01 mg/L.

The industrial value of bromophenol blue is reflected in the fields of dye synthesis and materials science
Dye intermediates: can be used as intermediates for synthesizing other dyes (such as azo dyes and anthraquinone dyes), introducing specific functional groups through bromine atom substitution reactions to enhance dye color fastness and photostability.
Material surface modification: By combining with metal oxides (such as TiO ₂, ZnO), the light absorption properties of the material can be controlled. For example, in dye-sensitized solar cells, as a photosensitizer, it absorbs visible light (maximum absorption wavelength of 422 nm) and improves cell efficiency through electron transfer.

With the integration of interdisciplinary technologies, their applications in emerging fields are gradually expanding:
Dye sensitized solar cells: As photosensitizers, efficient injection of photo generated electrons is achieved by binding carboxyl groups to the surface of TiO ₂ nanoparticles. Research has shown that the TiO ₂ electrode modified with bromophenol blue has a 2.3-fold increase in light absorption intensity in the visible light range (400-500 nm), providing new ideas for the development of low-cost solar cells.