Metacresol_purple

Metacresol purple

Metacresol purple

Chemical compound

Not to be confused with m-Cresol.

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]

Quick Facts Identifiers, Properties ...

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

References

  1. [1]
    "Capnography". LITFL • Life in the Fast Lane Medical Blog. Retrieved 2017-07-30.
  2. [2]
    "m-Cresol Purple 857890". Sigma-Aldrich. Retrieved 2017-07-30.
  3. [3]
    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.
  4. [4]
    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.
  5. [5]
    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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