Industrial Grade 99% Bromocresol green CAS 76-60-8

What is bromocresol green? What are its other uses?

1. What is Bromocresol Green?

Bromocresol green (BCG) is a tetrabromosulfonphthalein dye derived from triphenylmethane. It is also a classic acid-base indicator, and its chemical formula is usually written as:

C21H14Br4O5S (CAS No.: 76-60-8, molecular weight approximately 698.01, EINECS No.: 200-972-8)

It is a white or slightly yellow crystalline powder at room temperature, with a melting point of about 218~219℃ and a density of about 2.1 g/cm³. It is slightly soluble in water, soluble in ethanol, ether, ethyl acetate and benzene, and dissolves and develops color in alkaline aqueous solutions.

From a molecular structure perspective, bromocresol green consists of a sulfophthalein backbone and four bromine-substituted cresol rings, belonging to the triphenylmethane class of acid dyes. Its molecule undergoes a protonation/deprotonation transition under different pH conditions: it appears yellow below pH 3.8 and blue-green above pH 5.4—this "pH-responsive color change" characteristic makes it both a classic acid-base indicator and a biochemical chromogenic agent that specifically binds to serum albumin to form a blue-green complex, forming the dual basis for its widespread application in clinical testing and analytical chemistry.

Chemically, bromocresol green is stable, has a narrow color change range (pH 3.8–5.4), and exhibits a sharp color change. Its sodium salt aqueous solution can be used as a colorimetric reagent for pH determination using spectrophotometry, and it can also bind to proteins to develop color. It is irritating; avoid inhaling dust and skin contact. Store in a sealed, light-protected, and dry place.

Bromocresol green, excluding industrial-grade, refers to products geared towards clinical testing, analysis, and research applications. These primarily include indicator-grade (reagent-grade) products with a purity generally above 99%. Compared to industrial-grade products, these specifications place greater emphasis on the following indicators:

purity

Indicator-grade reagents require a main content of 99% or higher to ensure the accuracy of clinical testing and experimental results.

Color change range

The core performance indicators are a color change range of pH 3.8~5.4 (yellow to blue-green) and a sensitive color change.

Sensitivity

Sensitivity determines an indicator's ability to respond to minute changes in acidity and alkali and protein binding, and must meet indicator-grade specifications.

Solubility

It should be slightly soluble in water and soluble in solvents such as ethanol. The sodium salt solution should be clear, stable in color development, and ensure the reagent preparation performance.

What other uses does Bromocresol green have?

1. Serum albumin measurement (clinical laboratory, core application)

The bromocresol green method (BCG method) is a classic clinical method for determining serum albumin: in a pH 4.0 environment, in the presence of nonionic surfactants, bromocresol green forms a blue-green complex with albumin. The intensity of the color is directly proportional to the albumin content, making it an important method for biochemical testing.

2. Laboratory acid-base indicators (reagent grade)

Bromocresol green is one of the most classic acid-base indicators in analytical chemistry. Its color change range is pH 3.8 to 5.4 (yellow to blue-green). It has a sharp color change and clear boundaries, and is widely used in acid-base titration analysis and pH determination. Its sodium salt aqueous solution is also used as a colorimetric reagent for spectrophotometric pH determination.

3. Microbial culture medium indicators

Bromocresol green is used as a pH indicator in microbial culture media. It visually indicates bacterial growth and acid production through color changes and is applied in food microbiology testing and bacterial culture in biological laboratories.

4. Reagents for Thin-Layer Chromatography and Spectrophotometry

Bromocresol green is used as a colorimetric reagent in thin-layer chromatography for the determination of aliphatic hydroxy acids and alkaloids, and also as an extraction and separation agent in spectrophotometric determination of quaternary ammonium cations, serving analytical chemistry.

5. Water quality monitoring (core application)

( 1 ) Bromocresol green is an acid-base indicator used for testing the quality of industrial water. It can monitor the change of pH value of boiler water, circulating water and process water, timely find the abnormal situation of water quality and prevent equipment from corrosion and scaling. It is an important reagent for testing in industrial water treatment and water quality management.

( 2 ) Swimming pool water pH testing and public water treatment industry The test reagent containing bromocresol green is used to quickly determine the acidity and alkalinity of the water body, so as to ensure that the swimming pool water quality meets the standards and protect the public health.

6. Food and beverage industry testing

Food and beverage manufacturers use bromocresol green for quality testing and control of product pH levels, helping to determine the pH status in processes such as fermentation and blending. It is applied to quality inspection in industries such as beverages and dairy products.

7. Electroplating and Surface Treatment Process Control

Bromocresol green is used in electroplating and metal surface treatment operations for the rapid detection and process control of the pH of the plating solution, to maintain the stability of the acidity and alkalinity of the plating solution, and to ensure the quality of the coating.

8. Chemical production process testing

Bromocresol green is used in chemical production processes to indicate and detect the acidity and alkalinity of reaction solutions, helping process engineers to determine the reaction progress and endpoint. It is applied in fine chemical production.

9. Indicator Production and Supply (Basic Raw Materials)

Industrial-grade bromocresol green is a basic raw material for the production of acid-base indicators, test reagents, and test strips. It is supplied to test reagent manufacturers for purification, solution preparation, and formulation, supporting the entire indicator industry chain.

It should be noted that indicator-grade specifications do not equate to "risk-free": bromocresol green is irritating, and when using reagent-grade products in experiments, laboratory safety regulations should be followed, protective equipment should be worn, and dust inhalation and skin contact should be avoided.

Summarize

Bromocresol green (BCG) is a white or slightly yellow crystalline powder of triphenylmethane. It is a classic acid-base indicator, changing from yellow to blue-green within a pH range of 3.8 to 5.4, with a sharp and clear color change. In daily life, we indirectly encounter it through medical examinations and biochemical tests, microbial culture and detection, water quality testing, and educational experiments. Beyond industry, bromocresol green is widely used in laboratory acid-base titration indicators, pH indicators for microbial culture media, thin-layer chromatography and spectrophotometric analysis reagents, and educational experiments, serving as an important acid-base indicator bridging "daily use" and "analytical chemistry and microbiology."