Phenol red (phenolsulfonphthalein, PH R) belongs to the class of triphenylmethane dyes. It is a waterͰsoluble anionic dye, mostly used as a pH indicator in cell biology laboratories. Also, in different protocols, it is used to detect H2O2(Hydrogen peroxide).

Phenol red can be used as a:

Dye in the preparation of phenol red/n-Si photodiode [phenol red/n-type silicon wafer] by spin coating technique. The device is appropriate for photo-detection applications.

Color-changing dye in the design of fiber optic pH sensor because as the acidity increases, the dye′s absorption properties shift from the green to the blue section of the spectrum.

Indicator in the determination of freshwater pH.

Appearance of solution: passes test

1st transition range: pH 1.2 - pH 3.0brownish orange - yellow

2nd transition range: pH 6.5 - pH 8.0brownish yellow - red violet

Loss on drying (110 °C): ≤ 1

Transition range (according to ACS): passes test

ACS conforms