Sigma-Aldrich Cresol Red Indicator Grade

Cresol Red, also known as o-cresol red, belongs to the phthalein and sulphonphthalein group of dyes. Cresol red changes color from orange to yellow at pH between 0.2-1.8 and yellow to violet at pH between 7.0-8.8. In alkaline solutions, cresol red is present as a hydrophilic dianion. The dianion is small and is violet in color, possessing a larger conjugated system than the yellow hydroxyquinone.

Cresol Red is a widely used pH indicator for routine pH assessments like microbial culture media preparations. In addition, Cresol red is a suitable constituent of PCR reagent systems. Cresol Red is used as a tracking dye in DNA, RNA (agarose), and protein (polyacrylamide) electrophoresis.