Bromophenol blue

A pH indicator dye used in laboratories

Bromophenol blue is a chemical compound used as a pH indicator, a dye, and a color marker in various laboratory applications. It is a member of the sulfonphthalein family of dyes and is known for its ability to change color in response to pH changes.

Chemical Properties

Bromophenol blue is a triphenylmethane dye with the chemical formula C₁₉H₁₀Br₄O₅S. It appears as a pinkish crystalline powder and is soluble in water and ethanol. The dye exhibits a color change from yellow to blue over the pH range of 3.0 to 4.6.

Applications

pH Indicator

Bromophenol blue is widely used as a pH indicator in various chemical and biological experiments. It is particularly useful in titrations and other analytical procedures where monitoring pH changes is essential. The color transition from yellow to blue makes it easy to determine the endpoint of a titration.

Electrophoresis

In gel electrophoresis, bromophenol blue serves as a tracking dye. It is added to samples to monitor the progress of the electrophoresis run. The dye migrates through the gel at a predictable rate, allowing researchers to estimate the position of DNA or protein bands.

Dyeing and Staining

Bromophenol blue is also used as a dye in various staining protocols. It can be used to stain agarose gels and polyacrylamide gels, providing contrast to visualize the separation of biomolecules.

Mechanism of Action

The color change of bromophenol blue is due to the ionization of the sulfonphthalein group. At low pH, the dye is in its protonated form, appearing yellow. As the pH increases, the dye loses protons and shifts to its blue form. This reversible reaction is what makes bromophenol blue an effective pH indicator.

Safety and Handling

Bromophenol blue should be handled with care in the laboratory. It can cause irritation to the skin, eyes, and respiratory tract. Appropriate personal protective equipment such as gloves and goggles should be worn when handling the dye.

Related Pages

• pH indicator
• Gel electrophoresis
• Triphenylmethane dye
• Sulfonphthalein

Bromophenol blue gallery

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  Bromophenol Blue structure
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  Bromophenol blue cyclic 3D ball
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  Bromfenolová modř