Metacresol purple or m-cresol purple, also called m-cresolsulfonphthalein is a triarylmethane dye and a pH indicator. It is used as a capnographic indicator for detecting detect end-tidal carbon dioxide to ensure successful tracheal intubation in an emergency.
Bromocresol purple is a pH indicator which changes color from yellow (at low pH 5.2) to violet (above pH 6.8). It is mainly used as a fluorescent stain in yeast cells. It helps in dead cell count for cells with plasma membrane damage.
Bromocresol Purple Indicator Solution: Dissolve 50 mg of bromocresol purple in 0.92 ml of 0.1 M sodium hydroxide and 20 ml of ethanol (95 percent). After the solution is effected, add sufficient water to produce 100 ml.