Bromocresol purple (BCP) or 5′,5″-dibromo-''o''-cresolsulfophthalein, is a dye of the

triphenylmethane Triphenylmethane, or triphenyl methane, is the hydrocarbon with the formula (C6H5)3CH. This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is the basic skeleton of many synthetic dyes called triarylmeth ...

family (

triarylmethane dye Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes. Families Triarylmethane dyes can be grouped into families accordin ...

s) and a

pH indicator A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence, ...

. It is colored yellow below pH 5.2, and violet above pH 6.8. In its cyclic

sulfonate In organosulfur chemistry, a sulfonate is a salt or ester of a sulfonic acid. It contains the functional group , where R is an organic group. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non-o ...

ester form, it has a p''K''_a value of 6.3, and is usually prepared as a 0.04% aqueous solution.

Uses

Bromocresol purple is used in medical laboratories to measure

albumin Albumin is a family of globular proteins, the most common of which are the serum albumins. All the proteins of the albumin family are water-soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Albumins ...

. Use of BCP in this application may provide some advantage over older methods using

bromocresol green Bromocresol green (BCG) is a dye of the triphenylmethane family (triarylmethane dyes). It belongs to a class of dyes called sulfonephthaleins. It is used as a pH indicator in applications such as growth mediums for microorganisms and titrations. ...

. In microbiology, it is used for staining dead cells based on their acidity, and for the isolation and assaying of

lactic acid bacteria Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped ( bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...

. In

photographic processing Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image in ...

, it can be used as an additive to acid

stop bath Stop bath is a acidic solution used for processing black-and-white photographic films, plates, and paper. It is used to neutralize the alkaline developer, thus halting development. Stop bath is commonly a 2% dilution of acetic acid in water, tho ...

s to indicate that the bath has reached neutral pH and needs to be replaced. Bromocresol purple milk solids glucose agar is used as a medium used to distinguish

dermatophyte Dermatophyte (from Greek '' derma'' "skin" ( GEN ''dermatos'') and ''phyton'' "plant") is a common label for a group of fungus of ''Arthrodermataceae'' that commonly causes skin disease in animals and humans. Traditionally, these anamorphic (a ...

s from bacteria and other organisms in cases of

ringworm Dermatophytosis, also known as ringworm, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Symptoms begin four to fourteen days after exposure. Multiple a ...

fungus ('' T. verrucosum'') infestation in cattle and other animals.

pH Indicator

Similar to

, 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

structure that gives the solution a purple color. As the pH decreases, it converts to a

sultone In organosulfur chemistry, a sulfonate is a salt or ester of a sulfonic acid. It contains the functional group , where R is an organic group. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non-o ...

(cyclic sulfonic ester) that colors the solution yellow. In some microbiology tests, this change is used as an indicator of bacterial growth. : Bromkresolpurpur, Gleichgewicht

References

External links

{{Commons category
Material Safety Data Sheet
PH indicators Triarylmethane dyes Phenol dyes Bromoarenes Benzoxathioles

Uses

pH Indicator

See also

References

External links