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.[1][2] It can be used to measure the pH in subzero temperatures of saline or hypersaline media.[3]
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.017.237 |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C21H18O5S | |
| Molar mass | 382.43 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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In colorimetric capnography, the indicator is incorporated in an aqueous matrix that provides a pH just above the indicator's colour change.[4] When exposed to carbon dioxide (CO2), it undergoes a colour change from purple to yellow, because when CO2 dissolves in the matrix, it forms carbonic acid.[5]
In chemistry, it has two useful indicator ranges:[2]
- pH 1.2–2.8: red to yellow
- pH 7.4–9.0: yellow to purple
See also
editReferences
edit- ^ "Capnography". LITFL • Life in the Fast Lane Medical Blog. Retrieved 2017-07-30.
- ^ a b "m-Cresol Purple 857890". Sigma-Aldrich. Retrieved 2017-07-30.
- ^ Loucaides, Socratis; Rèrolle, Victoire M. C; Papadimitriou, Stathys; Kennedy, Hilary; Mowlem, Matthew C; Dickson, Andrew G; Gledhill, Martha; Achterberg, Eric P (2017). "Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures". Scientific Reports. 7 (1): 2481. Bibcode:2017NatSR...7.2481L. doi:10.1038/s41598-017-02624-0. PMC 5449408. PMID 28559544.
- ^ Gedeon, A.; Krill, P.; Mebius, C. (1994-09-01). "A new colorimetric breath indicator (Colibri)". Anaesthesia. 49 (9): 798–803. doi:10.1111/j.1365-2044.1994.tb04457.x. ISSN 1365-2044. PMID 7978140. S2CID 44501202.
- ^ Hagberg, Carin A. (2007-02-23). Benumof's Airway Management. Elsevier Health Sciences. ISBN 978-0323070171.
| Metacresol purple (pH indicator) | ||
| below pH 7.4 | above pH 9.0 | |
| 7.4 | ⇌ | 9.0 |
| Metacresol purple (pH indicator) | ||
| below pH 1.2 | above pH 2.8 | |
| 1.2 | ⇌ | 2.8 |
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