Bromocresol purple

Bromocresol purple (BCP) or 5′,5″-dibromo-o-cresolsulfophthalein, is a dye of the triphenylmethane family (triarylmethane dyes) and a pH indicator. It is colored yellow below pH 5.2, and violet above pH 6.8. In its cyclic sulfonate ester form, it has a pKa value of 6.3, and is usually prepared as a 0.04% aqueous solution.[1]

Bromocresol purple
Names
IUPAC name
4,4'-(1,1-Dioxido-3H-2,1-benzoxathiole-3,3-diyl)-bis(2-bromo-6-methylphenol)
Other names
5′,5″-Dibromo-o-cresolsulfonephthalein
Bromcresol purple
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.003.716
EC Number
  • 204-087-8
UNII
Properties
C21H16Br2O5S
Molar mass 540.22 g·mol−1
Appearance Purple powder
Melting point 241 to 242 °C (466 to 468 °F; 514 to 515 K) (decomposition)
< 0.1 %
Hazards
GHS pictograms
GHS Signal word Warning
GHS hazard statements
 H315, H319, H335
P261, P264, P271, P280, P302+352, P304+340, P305+351+338, P312, P321, P332+313, P337+313, P362, P403+233, P405, P501
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Uses
A sample of bromocresol purple in its violet form
Bromocresol purple (pH indicator)
below pH 5.2 above pH 6.8
5.2 ⇌ 6.8

Bromocresol purple is used in medical laboratories to measure albumin. Use of BCP in this application may provide some advantage over older methods using bromocresol green.[2][3] In microbiology, it is used for staining dead cells based on their acidity, and for the isolation and assaying of lactic acid bacteria.[4][5]

In photographic processing, it can be used as an additive to acid stop baths to indicate that the bath has reached neutral pH and needs to be replaced.[6]

Bromocresol purple milk solids glucose agar is used as a medium used to distinguish dermatophytes from bacteria and other organisms in cases of ringworm fungus (T. verrucosum) infestation in cattle and other animals.[7][8]

pH Indicator

Similar to bromocresol green, the structure of bromocresol purple changes with pH. Changing the level of acidity causes a shift in the equilibrium between two different structures that have different colors. In near-neutral or alkaline solution, the chemical has a sulfonate structure that gives the solution a purple color. As the pH decreases, it converts to a sultone (cyclic sulfonic ester) that colors the solution yellow.

See also

References
  1. "Bromocresol Purple". NCBI PubChem. National Center for Biotechnology Information.
  2. Bachmann, Lorin M.; Yu, Min; Boyd, James C.; Bruns, David E.; Miller, W. Greg (2017-03-01). "State of Harmonization of 24 Serum Albumin Measurement Procedures and Implications for Medical Decisions". Clinical Chemistry. 63 (3): 770–779. doi:10.1373/clinchem.2016.262899. ISSN 0009-9147. PMID 28073902.
  3. Ito, Shigenori; Yamamoto, Daisuke (2010-02-02). "Mechanism for the color change in bromocresol purple bound to human serum albumin". Clinica Chimica Acta. 411 (3): 294–295. doi:10.1016/j.cca.2009.11.019. PMID 19932090.
  4. Kurzweilová, H.; Sigler, K. (November 1993). "Fluorescent staining with bromocresol purple: a rapid method for determining yeast cell dead count developed as an assay of killer toxin activity". Yeast. 9 (11): 1207–1211. doi:10.1002/yea.320091107. PMID 7509098.
  5. Lee, H.M.; Lee, Y. (June 2008). "A differential medium for lactic acid-producing bacteria in a mixed culture". Letters in Applied Microbiology. 46 (6): 676–681. doi:10.1111/j.1472-765X.2008.02371.x. PMID 18444977.
  6. Anchell, Steve (2016). The Darkroom Cookbook (4 ed.). Routledge. ISBN 9781317337607 – via Google Books.
  7. Kane, J.; Summerbell, R.; Sigler, L.; Krajden, S.; Land, G. (1997). Laboratory Handbook of Dermatophytes: A Clinical Guide and Laboratory Handbook of Dermatophytes and Other Filamentous Fungi from Skin, Hair, and Nails. Belmont, CA: Star Publishing Company. ISBN 9780898631579.
  8. Beneke, E. S.; Rogers, A. L. (1996). Medical Mycology and Human Mycoses (illustrated ed.). Belmont, CA: Star Publishing Company. pp. 85–90. ISBN 9780898631753.
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