Bromocresol purple explained

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 pK_a value of 6.3, and is usually prepared as a 0.04% aqueous solution.^[1]

Uses

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. In some microbiology tests, this change is used as an indicator of bacterial growth.^{[9] [10]}

See also

• Metacresol purple

External links

• Material Safety Data Sheet

Notes and References

1. Web site: 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. en. 63. 3. 770–779. 10.1373/clinchem.2016.262899. 0009-9147. 28073902. free.
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. 10.1016/j.cca.2009.11.019. 19932090.
4. Fluorescent staining with bromocresol purple: a rapid method for determining yeast cell dead count developed as an assay of killer toxin activity. . Yeast . 1207–1211 . 9 . 11 . H. . Kurzweilová . K. . Sigler . November 1993 . 7509098 . 10.1002/yea.320091107. 44782970 .
5. A differential medium for lactic acid-producing bacteria in a mixed culture . Letters in Applied Microbiology . 676–681 . H.M. . Lee . Y. . Lee . June 2008 . 18444977 . 10.1111/j.1472-765X.2008.02371.x . 46 . 6 . free .
6. Book: Anchell, Steve . The Darkroom Cookbook . Google Books . 2016 . 4 . . 9781317337607.
7. Book: Kane. J.. Summerbell. R.. Sigler. L.. Krajden. S.. Land. G.. Laboratory Handbook of Dermatophytes: A Clinical Guide and Laboratory Handbook of Dermatophytes and Other Filamentous Fungi from Skin, Hair, and Nails. 1997. Star Publishing Company. Belmont, CA. 9780898631579.
8. Book: Beneke. E. S.. Rogers. A. L.. illustrated. Medical Mycology and Human Mycoses. 1996. Star Publishing Company. Belmont, CA. 9780898631753. 85–90.
9. Web site: Bromocresol Purple - an overview | ScienceDirect Topics.
10. Web site: Archived copy . 2022-02-15 . 2022-02-16 . https://web.archive.org/web/20220216042922/https://www.thomassci.com/FetchFile.ashx?id=2807195c-9bfc-46a6-b088-61dd6b1f3e42 . dead .