Products / pH Indicators


C.A.S. No. 115-40-2
M.F. C21H16Br2O5S
M.W. 540.24gm/mole


Dye Content (by Spectrophotometry) >95%
Transition Range pH 5.2-6.8
Solubility 0.1% (95% EtOH) Clear solution
Absorption maximum (pH 5.2) ?1max 427-431nm
Absorption maximum (pH 6.8) ?2max 588-590nm
Absorptivity (A1%/1cm at pH 5.2 at ?1max) 400-500
Absorptivity (A1%/1cm at pH 6.8 at ?2max) 1000-1100
Loss On Drying (110°C) <1%

Chemical Name

3,3-Bis(3-bromo-4-hydroxy-5-methylphenyl)-3H-benzo[c][1,2]oxathiole 1,1-dioxide

inChI Key


Product Description:

Bromocresol Purple is a water soluble dye used as an protein probe. It has been used in the spectrophotometric determination of serum-albumin. It is also a pH indicator with a transition interval from 5.2 - 6.8 (yellow to purple).


Soluble in alcohol, dilute alkalies. In water, 7.3X10^-3 mg/L at 25 deg C (est)


Bromocresol purple (BCP) or 5',5-dibromo-o-cresolsulfophthalein, is a pH indicator. In its sultone form, it has a pKa value of 6.3, and is usually prepared as a 0.04% aqueous solution. Besides its primary function as an indicator, bromocresol purple is used in medical laboratories to measure albumin. Used in spectrophotometric determination of serum-albumin.Bromocresol purple binds quantitatively with human serum albumin forming a stable complex with absorbance maximum at 600 nm. The intensity of the color produced is directly proportional to the albumin concentration in the sample.It is used for the confirmation tests for presence of fecal streptococci in water and wastewater.pH indicators and similar dyes which affinity allow to probe (detect, visualize and even measure) ) physiological parameter and biology structures, such as the intracellular pH, organelles or membrane lipids, the cytoskeleton, cytoplasmic Ca2+, caspases and enzymes

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