Cresol Red

Cresol Red is a sulfonephthalein dye commonly used as a pH indicator and tracking dye in biochemical and molecular biology applications. It is used as an indicator with the following transition intervals: pH 1.8 (orange) to pH 2.0 (yellow); pH 7.0 (yellow) to pH 8.8 (violet) and makes it a clear visual marker for monitoring pH changes in buffer systems and cell culture media. It is a widely used pH indicator for routine pH assessments like microbial culture media preparations. In molecular biology, Cresol Red is frequently added to DNA and RNA loading buffers for gel electrophoresis, where it migrates at a predictable rate, enabling visualization of sample progress without interfering with nucleic acids or enzymatic reactions. Its low UV absorbance and minimal impact on downstream analyses make it an ideal additive for electrophoresis workflows, PCR, and enzyme assays. Cresol Red is used as a tracking dye in DNA, RNA (agarose) and protein (polyacrylamide) electrophoresis. In agarose, Cresol Red runs with an apparent molecular size of approx. 125bp DNA. Cresol Red does not inhibit Taq polymerase.