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Fluorescein

CAS No.
2321-07-5
Chemical Name:
Fluorescein
Synonyms
SOLVENT YELLOW 94;CI 45350:1;Fluorecein;fluoresceine;KI201;S NO 880;YELLOW 7;CI 45350.1;NSC 667256;angiofluor
CBNumber:
CB7753558
Molecular Formula:
C20H12O5
Molecular Weight:
332.31
MDL Number:
MFCD00005050
MOL File:
2321-07-5.mol
MSDS File:
SDS
TDS File:
TDS
Last updated:2026-05-12 09:12:00
Product description Number Pack Size Price
Fluorescein European Pharmacopoeia (EP) Reference Standard Y0000796 120 mg $254
Fluorescein for fluorescence, free acid 46955 250mg $40.5
Fluorescein for fluorescence, free acid 46955 1g $161
Fluorescein for fluorescence, free acid 46955 100g $725
Fluorescein for fluorescence, free acid 46955 500g $1785
More product size

Fluorescein Properties

Melting point 320 °C(lit.)
Boiling point 429.44°C (rough estimate)
Density 1.2739 (rough estimate)
refractive index 1.5000 (estimate)
storage temp. room temp
solubility Solubility Insoluble in water, ether, benzene, chloroform; soluble in ethanol, methanol, acetone, Iethyl acetate, N,N-dimethylformamide
pka 2.2, 4.4, 6.7(at 25℃)
Colour Index 45350
form Powder
color Red to orange
PH Range Pink uorescence (4.0) to green uorescence (6.0)
Water Solubility insoluble
ε(extinction coefficient) ≥12000 at 282-286nm
≥39000 at 236-240nm
≥70000 at 488-492nm
λmax 493.5nm, 496nm, 460nm, 515nm
Merck 14,4159
BRN 94324
Henry's Law Constant 1.1×1011 mol/(m3Pa) at 25℃, HSDB (2015)
Stability Stable. Combustible. Incompatible with strong oxidizing agents.
Major Application Organic light-emitting diode, nanoparticles, liquid crystal display, oil products, lip make-up, nucleic acid synthesis, amplification, sequencing and cloning, diagnosis of diabetic retinopathy, detecting yeast, multidrug resistance, proteins, antiHCV antibodies, target genes, enzymatic activity, nerve agent, nucleic acid sequences, imaging lung cancer, prostate cancer
Biological Applications Detecting chromosomal aberration; diagnosing corneal diseases; marking/detecting insects; as antitumor agent; as antihistaminic agent; use in agriculture and plant cultivation; use in cosmetics; use in ophthalmology; as a substrate for measuring α-amylases activity, elastases activity, esterases activity, β-glucuronidases activity, horseradish peroxidases activity, kinases activity, monoamine oxidases (MAOs) activity, phosphatases activity, phospholipases activity, proteases/proteinases activity, telomerases activity activity
Cosmetics Ingredients Functions HAIR DYEING
COLORANT
InChI 1S/C20H12O5/c21-11-5-7-15-17(9-11)24-18-10-12(22)6-8-16(18)20(15)14-4-2-1-3-13(14)19(23)25-20/h1-10,21-22H
InChIKey GNBHRKFJIUUOQI-UHFFFAOYSA-N
SMILES Oc1ccc2c(Oc3cc(O)ccc3C24OC(=O)c5ccccc45)c1
LogP 2.980 (est)
FDA 21 CFR 74.1707; 74.2707; 82.1707
CAS DataBase Reference 2321-07-5(CAS DataBase Reference)
EWG's Food Scores 1
FDA UNII TPY09G7XIR
ATC code S01JA01,S01JA51
EPA Substance Registry System Fluorescein (2321-07-5)
UNSPSC Code 41116107
NACRES NA.47

SAFETY

Risk and Safety Statements

Symbol(GHS)  GHS hazard pictograms
GHS07
Signal word  Warning
Hazard statements  H319
Precautionary statements  P305+P351+P338
PPE Eyeshields, Gloves, type N95 (US)
Hazard Codes  Xi
Risk Statements  43-36-36/37/38
Safety Statements  22-24/25-37/39-26-36/37/39-27
WGK Germany  3
RTECS  LM5075000
10-21
TSCA  TSCA listed
HS Code  32042000
Storage Class 11 - Combustible Solids
Hazard Classifications Eye Irrit. 2
Hazardous Substances Data 2321-07-5(Hazardous Substances Data)
REACH Registrations Active
NFPA 704
0
2 0

Fluorescein price More Price(59)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich Y0000796 Fluorescein European Pharmacopoeia (EP) Reference Standard 2321-07-5 120 mg $254 2026-04-30 Buy
Sigma-Aldrich 46955 Fluorescein for fluorescence, free acid 2321-07-5 250mg $40.5 2026-04-30 Buy
Sigma-Aldrich 46955 Fluorescein for fluorescence, free acid 2321-07-5 1g $161 2026-04-30 Buy
Sigma-Aldrich 46955 Fluorescein for fluorescence, free acid 2321-07-5 100g $725 2026-04-30 Buy
Sigma-Aldrich 46955 Fluorescein for fluorescence, free acid 2321-07-5 500g $1785 2026-04-30 Buy
Product number Packaging Price Buy
Y0000796 120 mg $254 Buy
46955 250mg $40.5 Buy
46955 1g $161 Buy
46955 100g $725 Buy
46955 500g $1785 Buy

Fluorescein Chemical Properties,Uses,Production

Description

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 and serology to detect latent blood stains, and in dye tracing. Fluorescein has an absorption maximum at 494 nm and emission maximum 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 Properties

Orange-red, crystalline powder. Very dilute alkaline solutions exhibit intense greenishyellow fluorescence by reflected light, while the solution is reddish-orange by transmitted light.soluble in dilute alkalies, boiling alcohol, ether, dilute acids, and

Physical properties

The fluorescence of this molecule is very intense; peak excitation occurs at 494 nm and peak emission at 521 nm.
Fluorescein has a pKa of 6.4, and its ionization equilibrium leads to pH-dependent absorption 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 non intensity based measurements. The lifetimes can be recovered using time-correlated single photon counting or phase-modulation fluorimetry.

Uses

Fluorescein is used as a fluorescent tracer for many applications including in a type of dye laser as the gain medium, in forensics and serology to detect latent blood stains and in dye tracing. It is used to localise multiple muscular ventricular septal defects during open heart surgery and confirm the presence of any residual defects. It is applied to teeth to reveal plaque.

Uses

A fluorescent tracer used for many applications. It is used in ophthalmology as a tool in the diagnosis of corneal abrasions, corneal ulcers and herpetic corneal infections. It can attach to certain biologically active molecules, thus allowing biologists to target the fluorophore to specific proteins or structures within cells

Uses

corneal trama indicator

Definition

ChEBI: A xanthene dye that is highly fluorescent, detectable even when present in minute quantities. Used forensically to detect traces of blood, in analytical chemistry as an indicator in silver nitrate titrations and in microscopy.

Definition

A fluorescent dye used as an absorption indicator.

Application

Biochemical research
In cellular biology, the isothiocyanate derivative of fluorescein is often used to label and track cells in fluorescence microscopy applications (for example, flow cytometry). Additional biologically active molecules (such as antibodies) may also be attached to fluorescein, allowing biologists to target the fluorophore to specific proteins or structures within cells. This application is common in yeast display.
Health care applications
"Fluorescein sodium", the sodium salt of fluorescein, is used extensively as a diagnostic tool in the field of ophthalmology and optometry, where topical fluorescein is used in the diagnosis of corneal abrasions, corneal ulcers and herpetic corneal infections. It is also used in rigid gas permeable contact lens fitting to evaluate the tear layer under the lens.
Uses in river systems
In 1966, environmentalists forced a change to a vegetable-based dye to protect local wildlife. Other uses of fluorescein include using it as a water-soluble dye added to rainwater in environmental testing simulations to aid in locating and analyzing any water leaks, and in Australia and New Zealand as a methylated spirit dye.
Oil field application
Fluorescein dye solutions, typically 15 % active, are commonly used as an aid to leak detection during hydrostatic testing of sub sea oil and gas pipelines and other subsea infrastructure. Leaks can be detected by divers carrying ultraviolet lights.

General Description

Yellow amorphous solid or orange-red crystals. Latter have greenish-yellow fluorescence by reflected light. Insoluble in water. Soluble in dilute aqueous bases. Very dilute alkaline solutions exhibit intense, greenish-yellow fluorescence by reflected light. Low toxicity. May be sensitive to prolonged exposure to light.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

Fluorescein is incompatible with strong oxidizers. Also incompatible with acids, acid salts and salts of heavy metals. .

Fire Hazard

Flash point data for Fluorescein is not available, but Fluorescein is probably combustible.

Safety Profile

Poison by intravenous route. Moderately toxic by intraperitoneal route. Mutation data reported. When heated to decomposition it emits acrid smoke and irritating fumes. See also FLUORESCEIN SODIUM.

Safety

Topical, oral, and intravenous use of fluorescein can cause adverse reactions, including nausea, vomiting, hives, acute hypotension, anaphylaxis and related anaphylactoid reaction, causing cardiac arrest and sudden death due to anaphylactic shock.
The most common adverse reaction is nausea, due to a difference in the pH from the body and the pH of the sodium fluorescein dye; a number of other factors , however, are considered contributors as well. The nausea usually is transient and subsides quickly. Hives can range from a minor annoyance to severe, and a single dose of antihistamine may give complete relief. Anaphylactic shock and subsequent cardiac arrest and sudden death are very rare, but because they occur within minutes, a health care provider who uses fluorescein should be prepared to perform emergency resuscitation.

Synthesis

Fluorescein was first synthesized by Adolf von Baeyer in 1871. It can be prepared from phthalic anhydride and resorcinol in the presence of zinc chloride via the Friedel - Crafts reaction.
A second method to prepare fluorescein uses methanesulfonic acid as a Brnsted acid catalyst. This route has a high yield under milder conditions.

Derivatives

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. Penta fluoro phenyl esters (PFP) and tetra fluoro phenyl 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 carboxy naphtho fluorescein. These dyes, along with newer fluoro phores such as Alexa 488, Fluo Probes 488 and DyLight 488, have been tailored for various chemical and biological applications where higher photo stability, different spectral characteristics, or different attachment groups are needed.

85-44-9
108-46-3
2321-07-5
Synthesis of Fluorescein from Phthalic anhydride and Resorcinol
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View Lastest Price from Fluorescein manufacturers

Image Update time Product Price Min. Order Purity Supply Ability Manufacturer
Fluorescein pictures 2026-05-26 Fluorescein
2321-07-5
US $0.00 / KG 1KG 98%min 30tons/month WUHAN FORTUNA CHEMICAL CO., LTD
Fluorescein pictures 2026-05-11 Fluorescein
2321-07-5
US $56.00 / g 95.04% 10g TargetMol Chemicals Inc.
Fluorescein pictures 2026-05-11 Fluorescein
2321-07-5
US $56.00 / g 95.04% 10g TargetMol Chemicals Inc.
  • Fluorescein pictures
  • Fluorescein
    2321-07-5
  • US $0.00 / KG
  • 98%min
  • WUHAN FORTUNA CHEMICAL CO., LTD
  • Fluorescein pictures
  • Fluorescein
    2321-07-5
  • US $56.00 / g
  • 95.04%
  • TargetMol Chemicals Inc.
  • Fluorescein pictures
  • Fluorescein
    2321-07-5
  • US $56.00 / g
  • 95.04%
  • TargetMol Chemicals Inc.
FLUORESCEIN, FREE ACIDFLUORESCEIN, FREE ACIDFLUORESCEIN, FREE ACID Diresorcinolphthalein Tetraoxyphthalophenone anhydride SOLVENT YELLOW 94 S NO 880 RESORCINOL PHTHALEIN FLUORESCEIN, ALCOHOL SOLUBLE FLUORESCEIN CI 45350.1 CI 45350:1 CI NO 45350 D AND C YELLOW NO 7 3,6-dihydroxyspiro[isobenzofuran-1(3H),9-xanthen]-3-one Fluorescein Free Acid KI201 Fluorescein (200 mg) NSC 667256 FLUORESCEIN (C.I.45350) 25 G FLUORESCEIN (C.I.45350) 100 G YELLOW 7 Fluorescein, Indicator 3’,4’-dehydroxyfluoran 3’,6’-dihydroxy-fluora 3’,6’-dihydroxyfluoran 3’,6’-dihydroxyspiro(isobenzofuran-1(3h),9’(9h)-xanthen)-3-one 3’,6’-fluorandiol 9-(o-carboxyphenyl)-6-hydroxy-3h-xanthen-3-on 9-(o-carboxyphenyl)-6-hydroxy-3-isoxanthenone 9’-(9h)xanthen)-3-one,3’,6’-dihydroxy-spiro(isobenzofuran-1(3h 9’-(9H)xanthen]-3-one,3’,6’-dihydroxy-Spiro[isobenzofuran-1(3H) 9’-[9h]xanthen]-3-one,3’,6’-dihydroxy-spiro[isobenzofuran-1(3h angiofluor benzoicacid,2-(6-hydroxy-3-oxo-3h-xanthen-9-yl) c.i.45350(freeacid) c.i.45350a c.i.solventyellow94 d+cyellowno.7 dihydroxyfluorane fluoresceinacid fluoresceine fluoresceinred hidacidfluorescein japanyellow201 japanyellowno.201 o-(6-hydroxy-3-oxo-3h-xanthen-9-yl)-benzoicaci soapyellowf yellowfluorescein zlutkysela73 DNA-length standard I DNA-length standard II DNA-length standard III Fluorescein≥ 99%(dye content) Resorcinolphthalein Diresorcinolphthalein Dihydroxyfluorane Tetraoxyphthalophenone anhydride Acid Yellow 73 Eosin Fluorescein, Reag. Ph. Eur. 3′,6′-dihydroxy Uoran Cresorcinolphthalein Yellow  Uorescein Fluorescein *CAS 2321-07-5*