• USA Home
  • F9252 - Folin & Ciocalteu’s phenol reagent


F9252 Sigma-Aldrich

Folin & Ciocalteu’s phenol reagent

suitable for determination of total protein by Lowry method, 2 N


Frequently Asked Questions

Live Chat and Frequently Asked Questions are available for this Product.

Other Notes

Folin & Ciocalteu′s phenol reagent does not contain phenol. Rather, the reagent will react with phenols and non-phenolic reducing substances to form chromogens that can be detected spectrophotometrically.


This product is also available as part of a kit.


1 L in glass bottle

100, 500 mL in glass bottle


Folin & Ciocalteu′s phenol reagent is most commonly used in the Lowry method for determining protein concentration.1 In this method, protein is pretreated with copper(II) in a modified biuret reagent (alkaline copper solution
stabilized with sodium potassium tartrate). Addition of the phenol reagent generates chromogens that give increasing absorbance between 550-750 nm. Normally, absorbance at the peak (750 nm) or shoulder (660 nm) are used to quantitate protein concentrations between 1-100 mg/ml while absorbance at 550 nm is used to quantitate higher protein concentrations.
In the absence of copper, color intensity is determined primarily by the tyrosine and tryptophan content of the protein, and to a lesser extent by cysteine and histidine. Copper(II) has no effect on color formation by tyrosine, tryptophan, or histidine, but reduces color formation due to cysteine.1,2,3,4,5

Many modifications of the original assay procedure have been published,2 including methods for enhancing the color development,4,6 for determining the content of insoluble proteins,1,7 and for automating the procedure.8 Compounds including many buffers, chelating agents, detergents, and cyclic organic compounds can interfere with the Lowry protein assay.2
Folin & Ciocalteu′s phenol reagent can also be used as a spray reagent in chromatographic procedures.

Price and Availability

TruPAGE™ Pre-cast Polyacrylamide Gels

TruPAGE™ Pre-cast Polyacrylamide GelsTruPAGE Gels run true every time!

  • . 2-Year Shelf Life
  • . Superior Band Resolution
  • . Strong & Tear Resistant
  • . Higher Capacity Wells

Additional Products to Explore

for the determination of phenols

Gallic acid

97.5-102.5% (titration)

Sodium carbonate

ReagentPlus®, ≥99.5%

Customers Also Viewed

2 M (with respect to acid)

for the determination of phenols

Gallic acid

97.5-102.5% (titration)

Technical Service:

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

Bulk Ordering & Pricing:

Need larger quantities for your development, manufacturing or research applications?