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Fluorescein CAS 2321-07-5 Acid Yellow 73 CI 453501CI Solvent Yellow 94 

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Place of Origin: Zhejiang, China (Mainland) 
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Product Detail

Means of Transport: Ocean,Land,Air
Packing: According to the customer r...
Brand Name: MOSINTER
Molecular formula: C20H12O5
Soluble: insoluble
Storage condition: -20°C
Production Capacity: 100 Tons/year
Delivery Date: within 7 days
CAS No.: 2321-07-5
Molar mass: 332.31 g/mol
Density: 1.602 g/mL
Melting point: 314 - 316 °C

adsorption indicator;oxidation-reduction indicator;Fluorescent photometric analysis of sulfur ions

Fluorescein (CAS: 2321-07-5)




Orange-red   crystals



Melting point ℃


Basic Information

Fluorescein is a synthetic organic compound available as a dark orange/red powder slightly soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications.

Fluorescein is a fluorophore commonly used in microscopy, in a type of dye laser as the gain medium, in forensics andserology to detect latent blood stains, and in dye tracing. Fluorescein has an absorption maximum at 494 nm and emissionmaximum of 521 nm (in water). The major derivatives are fluorescein isothiocyanate (FITC) and, in oligonucleotide synthesis, 6-FAM phosphoramidite.

Fluorescein also has an isosbestic point (equal absorption for all pH values) at 460 nm. Fluorescein is also known as a color additive (D&C Yellow no. 7). The disodium salt form of fluorescein is known as uranine or D&C Yellow no. 8.

The color of its aqueous solution varies from green to orange as a function of the way it is observed: by reflection or by transmission, as it can be noticed in bubble levels in which fluorescein is added as a colorant to the alcohol filling the tube to increase the visibility of the air bubble and the precision of the instrument. More concentrated solutions of fluorescein can even appear red.

Chemical and physical properties

The fluorescence of this molecule is very intense; peak excitation occurs at 494 nmand peak emission at 521 nm.

Fluorescein has a pKa of 6.4, and its ionization equilibrium leads to pH-dependentabsorption and emission over the range of 5 to 9. Also, the fluorescence lifetimes of the protonated and deprotonated forms of fluorescein are approximately 3 and 4 ns, which allows for pH determination from nonintensity based measurements. The lifetimes can be recovered using time-correlated single photon counting or phase-modulationfluorimetry.


There are many fluorescein derivatives. For example, fluorescein isothiocyanate 1, often abbreviated as FITC, is the original fluorescein molecule functionalized with an isothiocyanate group (-N=C=S), replacing a hydrogen atom on the bottom ring of the structure. This derivative is reactive towards primary amine groups of biologically relevant compounds including intracellular proteins to form a thiourea linkage. A succinimidyl ester functional group attached to the fluorescein core, creating NHS-fluorescein, forms another common amine-reactive derivative, yielding more stable amide adducts. Pentafluorophenyl esters (PFP) and tetrafluorophenyl esters (TFP) are other useful reagents. In oligonucleotide synthesis, several phosphoramidite reagents containing protected fluorescein, e.g. 6-FAM phosphoramidite 2, are widely used for the preparation of fluorescein-labeled oligonucleotides.

Other green dyes include Oregon Green, Tokyo Green, SNAFL, and carboxynaphthofluorescein. These dyes, along with newerfluorophores such as Alexa 488, FluoProbes 488 and DyLight 488, have been tailored for various chemical and biological applications where higher photostability, different spectral characteristics, or different attachment groups are needed.

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Business Type:Manufacturer, Trading Company
City: Ningbo
Province/State: Zhejiang
Country/Region: China (Mainland)

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