Industrial-grade 99% Bromocresol Purple 115-40-2

Product Overview

Bromocresol purple (BCP) is a sulfonephthalein indicator dye supplied as a purple crystalline powder with a sharp, reproducible color transition — yellow below pH 5.2, purple above pH 6.8 (pKa ≈ 6.3). It is one of the standard acid–base indicators of analytical chemistry, chosen wherever a clear yellow-to-purple signal is needed in the near-neutral window.

Beyond titration chemistry, BCP has two major specialized roles: it is the reagent of the bromocresol-purple method for serum-albumin determination in clinical laboratories — favored over bromocresol green for its higher specificity and fewer interferences — and a metabolic indicator in microbiological culture media, where acid production by growing organisms turns the medium from purple to yellow. One dye, three established analytical professions.

A single dye, four core value propositions:

pH Indicators:

● a sharp acid–base indicator with a 5.2 – 6.8 (yellow → purple) transition for titration and pH testing;

Diagnostic & Clinical Assays:

● the reagent of the BCP method for serum-albumin measurement in clinical chemistry;

Microbiology & Culture Media:

● a metabolic indicator of acid production in selective and differential culture media;

Analytical & Staining Applications:

● an adsorption indicator, fluorescent dead-cell stain and general laboratory reagent.

Product Information (Quick Facts)

Chemistry & Forms

BCP belongs to the sulfonephthalein (sulfophthalein) family: a triphenylmethane core with two brominated cresol rings and a sulfonic acid group. In acid, the molecule is undissociated and yellow; as pH rises past the pKa (≈ 6.3), the phenolic hydroxyl ionizes and the conjugated system extends, shifting the color to purple. The two bromine substituents and the sulfonate group give the dye its water/ethanol solubility and its sharp, stable color change.

Commercial BCP is offered as the free-acid form (this product) and as the sodium salt, at dye contents from about 90% (indicator grade) up to high-purity ACS and BioReagent grades. Standard solutions are prepared as 0.04% aqueous or ethanolic indicator solutions, typically by dissolving the powder in dilute sodium hydroxide and diluting

Key Features & Benefits

● Sharp pH transition: reproducible yellow-to-purple change across 5.2 – 6.8 (pKa ≈ 6.3), ideal for near-neutral titrations.

● Clinically proven albumin assay: the BCP dye-binding method is a standard, more specific alternative to bromocresol green.

● Clear metabolic signaling: yellow-on-acid response makes fermentation and acid production instantly visible in culture media.

● Stable and reproducible: consistent transition interval and color intensity batch to batch.

● Multiple application forms: free acid or sodium salt; aqueous or ethanolic indicator solutions.

● Broad laboratory use: titration, pH testing, clinical chemistry, microbiology and staining from one dye.

Main Applications

1 pH Indicators (Core Application)

BCP is a standard acid–base indicator of the analytical laboratory:

● Titration: endpoint indicator for acid–base titrations whose equivalence point falls in the 5.2 – 6.8 window;

● pH test papers and strips: component of multi-range pH indicator papers;

● Solution pH monitoring: colorimetric pH checks in laboratory and process water;

● Education and quality control: a classic, easy-to-read indicator for teaching and routine testing.

2 Microbiology & Culture Media

● Fermentation indicator: detects acid production by bacteria, yeasts and molds in culture;

● Selective media: component of media such as azide glucose broth for enterococci detection;

● Lactic-acid-bacteria media: pH indicator in MRS-type and dairy culture formulations;

● Microbial identification: color-change discrimination in differential media.

3 Analytical & Staining Applications

● Adsorption indicator: endpoint indicator in precipitation titrations;

● Dead-cell staining: fluorescent staining of dead cells in microscopy and viability studies;

● Protein-binding probe: dye-binding studies and protein quantification in research;

● General laboratory reagent: pH and colorimetric applications across analytical chemistry.

Packaging, Storage

Packaging (customizable):

● 100 g laboratory bottles, 500 g / 1 kg HDPE containers, 25 kg fiber drum;

● Custom pack sizes on request.

Storage:

● Keep in a cool, dry, well-ventilated area away from direct sunlight and heat;

● Keep containers tightly closed to prevent moisture pick-up and contamination;

● Store away from strong oxidizers and incompatible materials;

● Recommended storage temperature 5 °C – 35 °C.

Why Choose Jinan Future Chemical Co., Ltd.?

● Factory-direct supply: own production capacity, transparent pricing, no middleman markup;

● Stable quality: strict internal control, every batch tested, COA with every shipment; small trial orders accepted.

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● Export experience: familiar with sea/air shipping documentation for chemical commodities, complete paperwork support;

● Fast response: quotations and technical support (COA, solution preparation advice) within 24 hours;

FAQ

Q1: What is bromocresol purple used for?

BCP is used as an acid–base indicator with a 5.2 – 6.8 (yellow-to-purple) transition in titrations and pH testing; as the dye-binding reagent for serum-albumin determination in clinical laboratories; as a metabolic indicator in microbiological culture media; and as an adsorption indicator and dead-cell stain in analysis.

Q2: What is the difference between bromocresol purple and bromocresol green?

Both are sulfonephthalein dyes, but they differ in substitution and transition window: BCG changes at pH 3.8 – 5.4 (yellow to blue), while BCP changes at pH 5.2 – 6.8 (yellow to purple). For albumin measurement, BCP is generally preferred because its dye–protein binding is more albumin-specific with fewer interferences

Q3: How do I prepare a BCP indicator solution?

A standard 0.04% solution is prepared by dissolving the powder in dilute sodium hydroxide (or ethanol) and diluting with water; typical recipes use about 0.1 g of BCP in a small volume of 0.01 N NaOH, made up to 250 mL with water. For clinical albumin assays, follow the reagent-kit or method-specification protocol of your system.

Q4: Is bromocresol purple safe to handle?

BCP has low acute toxicity, but the powder can irritate the eyes, skin and respiratory tract, and inhaled dye dust should be avoided. Use gloves, goggles and dust protection when handling, and avoid ingestion. It is a laboratory/industrial reagent, not a food ingredient; diagnostic use is governed by the destination market's regulations and the customer's own validated protocols.