Phenol Red Indicator Solution

It is typically used in cell culture media at 11 mg/L. A solution of phenol red will have a yellow color at a pH of 6.4 or below and a red color at a pH of 8.2 and above.Phenol red in tissue culture media can act as a weak estrogen, especially with human breast cancer cells. Lipophilic impurities, not the phenol red dye itself, account for the estrogenic activity. 95-99% of these impurities can be removed from the sodium salt of phenol red with a reduction in estrogen-like activity.