m-Cresol Purple acts as a pH indicator dye. It plays an important role in spectrophotometric pH measurements. It operates in the pH ranges 1.2 - 2.8 (red to yellow) and 7.4 - 9.0 (yellow to violet). Further, it is employed to stain epithelial cells and proteins.
Schutting, S.; Jokic, T.; Strobl, M.; Borisov, S. M.; de Beer, D.; Klimant, I. NIR optical carbon dioxide sensors based on highly photostable dihydroxy-aza-BODIPY dyes. J. Mater. Chem. C 2015, 3, 5474-5483.
Yost, R. A.; Bergeron, B. E.; Kirkpatrick, T. C.; Roberts, M. D.; Roberts, H. W.; Himel, V. T.; Sabey, K. A. Evaluation of 4 Different Irrigating Systems for Apical Extrusion of Sodium Hypochlorite. J. Endod. 2015, 41 (9), 1530-1534.