Description

Cresol Purple CAS NO 2303-01-7 is a high-purity sulfonphthalein dye widely used as a sensitive pH indicator in analytical chemistry and biological research. Its distinct color transition across a critical pH range makes it an indispensable tool for precise endpoint determination in titrations and for monitoring biochemical reactions. This product is essential for professionals in pharmaceutical quality control, academic research laboratories, and industrial chemical analysis who require reliable and consistent performance in their methodologies.

Application

• pH Indicator in Titrimetry: Primary use as a visual and spectrophotometric endpoint indicator in acid-base titrations, particularly within its transition range of pH 1.2 (red) to pH 2.8 (yellow) and pH 7.4 (yellow) to pH 9.0 (purple).
• Microbiological & Cell Culture Media: Used as a pH indicator in various prepared culture media to monitor metabolic activity and ensure optimal growth conditions for microorganisms and cell lines.
• Biochemical & Diagnostic Reagents: A key component in the formulation of diagnostic kits and biochemical assay buffers where precise pH monitoring is critical for accurate results.
• Research & Development: Employed in academic and industrial R&D for studying enzyme kinetics, proton transport mechanisms, and other pH-sensitive processes.
• Educational Laboratories: Serves as a standard teaching tool in university and college chemistry courses to demonstrate pH concepts and titration techniques.
• Quality Control in Manufacturing: Applied in the pharmaceutical and fine chemical industries for in-process checks and final product testing that requires pH measurement.

Basic Information

Product Name	Cresol Purple
CAS No.	2303-01-7
Molecular Formula	C21H18O5S
Molecular Weight	382.43 g/mol
Synonyms	o-Cresolsulfonphthalein; Cresol Purple Indicator; 4,4'-(3H-2,1-Benzoxathiol-3-ylidene)bis(2-methylphenol) S,S-Dioxide; m-Cresol Purple (common name for the mixed isomer); NSC 6692; C.I. 42525; o-Cresol Sulfonphthalein; 3',3''-Dimethylphenolsulfonphthalein
EINECS	218-971-6

Quality Control

Our Cresol Purple is manufactured under a strict quality management system to ensure batch-to-batch consistency and high performance. Each lot is tested to confirm identity, purity, and suitability for use as a precise pH indicator. A comprehensive Certificate of Analysis (COA) detailing specific test results, including assay by titration and spectral characteristics, is provided with every shipment to support your quality and regulatory requirements.

Storage

Preserve in a tightly closed container, protected from light. Store in a cool, dry, and well-ventilated area at a controlled room temperature (15-25°C). Keep away from heat sources and incompatible materials. The product is light-sensitive and should be stored away from direct light exposure to maintain stability.

Specification

Item	Specification
Appearance	Dark green powder or crystals
Identification (IR)	Conforms to structure
Identification (UV-Vis)	Characteristic absorption spectrum
Assay (Titration)	≥ 95.0%
pH Transition Range	1.2 (red) - 2.8 (yellow) and 7.4 (yellow) - 9.0 (purple)
Loss on Drying	≤ 2.0 %
Residue on Ignition (Sulfated Ash)	≤ 0.5 %
Suitability Test (as pH indicator)	Passes test

Note: Specifications can be tailored. Please contact us for the detailed technical data sheet of a specific grade.