Bromocresol green
{{short description|Chemical dye and pH indicator}}
{{chembox
| Watchedfields = changed
| verifiedrevid = 414034508
| ImageFile = Bromocresol green.svg
| ImageSize =
| ImageAlt = Skeletal formula of bromocresol green in cyclic form
| ImageFile1 = Bromocresol green cyclic 3D ball.png
| ImageAlt1 = Ball-and-stick model of the bromocresol green molecule in cyclic form
| PIN = 3,3-Bis(3,5-dibromo-4-hydroxy-2-methylphenyl)-2,1λ6-benzoxathiole-1,1(3H)-dione
| OtherNames = 3,3′,5,5′-Tetrabromo-m-cresolsulfonphthalein
Bromcresol green
|Section1={{Chembox Identifiers
| IUPHAR_ligand = 4530
| Abbreviations = BCG
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 6209
| EC_number = 200-972-8
| UNII = 8YGN0Y942M
| InChI = 1/C21H14Br4O5S/c1-9-12(7-14(22)19(26)17(9)24)21(13-8-15(23)20(27)18(25)10(13)2)11-5-3-4-6-16(11)31(28,29)30-21/h3-8,26-27H,1-2H3
| InChIKey = FRPHFZCDPYBUAU-UHFFFAOYAS
| ChEMBL_Ref = {{ebicite|correct|EBI}}
| ChEMBL = 145704
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C21H14Br4O5S/c1-9-12(7-14(22)19(26)17(9)24)21(13-8-15(23)20(27)18(25)10(13)2)11-5-3-4-6-16(11)31(28,29)30-21/h3-8,26-27H,1-2H3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = FRPHFZCDPYBUAU-UHFFFAOYSA-N
| CASNo = 76-60-8
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 6451
| SMILES = Brc1cc(c(c(Br)c1O)C)C3(OS(=O)(=O)c2ccccc23)c4cc(Br)c(O)c(Br)c4C
}}
|Section2={{Chembox Properties
| C=21 | H=14 | O=5 | S=1 | Br=4
| Appearance = Beige to brown powder
| Odor = Odorless
| Density =
| MeltingPtC = 225
| MeltingPt_notes = decomposes{{cite web|url=http://www.sigmaaldrich.com/catalog/product/sial/114359| title=Bromocresol Green|publisher=Sigma Aldrich}}
| BoilingPt =
| pKa = 4.90Kolthoff, I.M. Treatise on Analytical Chemistry, New York, Interscience Encyclopedia, Inc., 1959.
| Solubility = Sparingly soluble
| SolubleOther = Soluble in benzene; very soluble in ethanol and diethyl ether{{cite web | url = http://chemicalland21.com/specialtychem/finechem/BROMOCRESOL%20GREEN.htm | title = Bromocresol green }}
| Solvent = other solvents
}}
|Section3={{Chembox Hazards
| MainHazards =
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|315|319|335}}
| PPhrases = {{P-phrases|}}
| NFPA-H = 2
| NFPA-F = 1
| FlashPt =
| AutoignitionPt =}}
}}
{{pH_indicator_template|indicator_name=Bromocresol green|low_pH=3.8|high_pH=5.4|low_pH_color=yellow|high_pH_color=blue|high_pH_text=white}}
Bromocresol green (BCG) is a dye of the triphenylmethane family (triarylmethane dyes). It belongs to a class of dyes called sulfonephthaleins.{{Cite book|title=Handbook of Acid-Base Indicators|url=https://archive.org/details/handbookacidbase00sabn|url-access=limited|last=Sabnis|first=R. W.|publisher=CRC Press|year=2008|location=Boca Raton, FL|pages=[https://archive.org/details/handbookacidbase00sabn/page/n59 43]–44|isbn=9780849382185}} It is used as a pH indicator in applications such as growth mediums for microorganisms and titrations. In clinical practise, it is commonly used as a diagnostic technique. The most common use of bromocresol green is to measure serum albumin concentration within mammalian blood samples in possible cases of kidney failure and liver disease. In chemistry, bromocresol green is used in Thin-layer chromatography staining solutions to visualize acidic compounds.
Properties
File:Bromocresolo.jpgIn aqueous solution, bromocresol green will ionize to give the monoanionic form (yellow), that further deprotonates at higher pH to give the dianionic form (blue),{{cite web|url=http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml|title=Acid-Base Indicators|publisher=Frostburg State University Dept. of Chemistry|author=Fred Senese}} which is stabilized by resonance:
The acid dissociation constant (pKa) of this reaction is 4.8.{{Cite journal | doi = 10.1016/j.talanta.2007.11.022| pmid = 18585121| title = Integration of analytical measurements and wireless communications—Current issues and future strategies| journal = Talanta| volume = 75| issue = 3| pages = 606–12| year = 2008| last1 = Diamond | first1 = D. | last2 = Lau | first2 = K. T. | last3 = Brady | first3 = S. | last4 = Cleary | first4 = J. }} Tap water is sufficiently basic to give a solution of bromocresol green its characteristic blue-green color.Anonymous. Bromocresol Green. In The Merck index : an encyclopedia of chemicals, drugs, and biologicals; Windholz, M., Ed.; Merck & Co., Inc.: Rahway, N.J., 1983; pp 191.
File:Bromocresol green spectrum.png occurs where the acid and basic forms and mixtures thereof have the same absorbance]]
The acid and basic forms of this dye have an isosbestic point in their UV-Visible spectrum, around 515 nm, indicate that the two forms interconvert directly without forming any other substance.
An ethanol solution (0.04 wt%) of bromocresol green has been proposed for TLC staining and is suitable for visualisation of the compounds with functional groups whose pKa is below 5.0 (carboxylic acids, sulfonic acids, etc.). These appear as yellow spots on a light or dark blue background; no heating is necessary. Bromophenol blue solution can be used for the same purpose.
The compound is synthesized by bromination of cresol purple (m-cresolsulfonphthalein).
Uses
It is used as a pH indicator and as a tracking dye for DNA agarose gel electrophoresis. It can be used in its free acid form (light brown solid), or as a sodium salt (dark green solid). It is also an inhibitor of the prostaglandin E2 transport protein. Additional applications include use in sol-gel matrices,{{Cite journal|last=Zaggout|first=Farid R.|date=2005-11-01|title=Encapsulation of Bromocresol Green pH Indicator into a Sol-Gel Matrix|journal=Journal of Dispersion Science and Technology|volume=26|issue=6|pages=757–761|doi=10.1081/DIS-200063087|s2cid=97939147|issn=0193-2691}} the detection of ammonia,{{Cite journal|last1=Hoang|first1=Anh Tuan|last2=Cho|first2=Yeong Beom|last3=Park|first3=Joon-Shik|last4=Yang|first4=Yoonseok|last5=Kim|first5=Yong Shin|date=2016-07-01|title=Sensitive naked-eye detection of gaseous ammonia based on dye-impregnated nanoporous polyacrylonitrile mats|journal=Sensors and Actuators B: Chemical|volume=230|issue=Supplement C|pages=250–259|doi=10.1016/j.snb.2016.02.058}} and the measurement of albumin in human plasma and serum.{{Cite web|url=https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Bulletin/2/mak124bul.pdf|title=BCG (Bromocresol Green) Albumin Assay Kit|date=2014|website=Sigma Aldrich}}
Safety
Bromocresol green may cause irritation. Skin and eye contact should be avoided.