EDTA (Ethylenediaminetetraacetic Acid) | CAS 60-00-4 | ≥98%

Technical Specifications

Product Description & Scientific Applications

EDTA (ethylenediaminetetraacetic acid; edetic acid; H4EDTA) is a hexadentate aminopolycarboxylic acid chelator used for divalent- and trivalent-metal-ion control in molecular biology, biochemistry, analytical chemistry, cell culture, and laboratory sample preparation. Its two amine nitrogens and four carboxylate groups, in the fully deprotonated Y4− form, wrap around a metal centre to give octahedral cage-like complexes with high formation constants (log Kf approximately 10.7 for Ca2+, 8.7 for Mg2+, 16.5 for Zn2+, 18.8 for Cu2+, and 25 for Fe3+ at 25 °C, I = 0.1 M). EDTA is a hexaprotic weak acid (H6Y2+ in the fully protonated form), so the conditional stability constant Kf' depends strongly on the αY4− fraction, making working pH central to every EDTA titration and EDTA-based molecular biology buffer. The free acid has limited aqueous solubility, requiring alkaline adjustment with NaOH or KOH to dissolve at working concentrations; the more soluble disodium-dihydrate and tetrasodium salts are alternatives for direct preparation. EDTA binds Ca2+ and Mg2+ with comparable affinity, so when Ca2+-selective chelation is required in the presence of physiological Mg2+, EGTA is preferred for its much larger Ca2+/Mg2+ binding-constant differential.

Metal Chelation for Nucleic Acid Protection and Enzyme Control

EDTA is the standard divalent-cation sequestrant in molecular biology buffers, where it suppresses the activity of Mg2+- and Ca2+-dependent enzymes — including DNases, divalent-metal-dependent RNases, and metalloproteases — by lowering the free metal-ion concentration below their catalytic threshold. This underlies its presence in the canonical nucleic acid storage and electrophoresis buffers: TE (10 mM Tris-HCl, 1 mM EDTA, pH 8.0) for DNA storage and nuclease-sensitive nucleic-acid handling, and TAE (1×: 40 mM Tris-acetate, 1 mM EDTA, pH about 8.3) and TBE (1×: 89 mM Tris, 89 mM borate, 2 mM EDTA, pH about 8.3) for agarose and polyacrylamide electrophoresis. The same logic underlies EDTA-containing stop solutions for restriction-enzyme digests, ligations, and PCR, and EDTA inclusion in plasmid- and genomic-DNA lysis buffers and RNA isolation protocols. EDTA is specifically excluded from active PCR and reverse-transcription mixes, however, because it would sequester the Mg2+ cofactor required for polymerase activity.

Cell Dissociation and Adhesion Control in Cell Culture

EDTA is used to weaken Ca2+- and Mg2+-dependent cell adhesion in mammalian cell-culture workflows. Cadherin-mediated cell–cell contacts require extracellular Ca2+ for their homophilic engagement, and integrin-mediated cell–substrate interactions depend on Ca2+, Mg2+, and Mn2+ bound at the metal-ion-dependent adhesion site (MIDAS); sequestration of these cations by EDTA disrupts both adhesion classes simultaneously. Common formulations pair 0.05% or 0.25% trypsin with approximately 0.5–1 mM EDTA in Ca2+/Mg2+-free balanced salt solution, so trypsin can access cleavable peptide bonds more efficiently once adhesion contacts are weakened. Enzyme-free EDTA-in-PBS formulations (typically 0.5–5 mM) are used for surface-antigen-sensitive workflows such as flow-cytometry sample preparation, primary-cell dissociation where receptor integrity matters, and stem-cell passaging where trypsin exposure should be minimised.

Hematology Anticoagulant and Histology Decalcification

Dipotassium and tripotassium EDTA salts (K2EDTA and K3EDTA) are the standard anticoagulant additives in lavender-top blood collection tubes, since chelation of Ca2+ blocks the calcium-dependent steps of the coagulation cascade and stabilises blood-cell morphology. EDTA-anticoagulated whole blood is the matrix of choice for complete blood counts, leukocyte differential analysis, peripheral-blood-smear morphology, and flow-cytometric immunophenotyping; spray-dried K2EDTA is commonly preferred for hematology tubes because it minimises liquid dilution effects compared with liquid K3EDTA formulations. In histology, 10% EDTA buffered to pH 7.4 is the preferred decalcifying solution for bone, teeth, and other mineralised samples when antigenicity and nucleic-acid integrity must be preserved: chelation removes calcium phosphate gradually at near-neutral pH, in contrast to formic, nitric, or hydrochloric acids, and decalcified samples retain protein epitopes and DNA/RNA quality sufficient for immunohistochemistry, in situ hybridisation, and PCR.

Complexometric Analysis of Metal Ions

EDTA is the classical reagent for complexometric titration. The aminopolycarboxylate framework supports multidentate binding to almost all di- and trivalent metal cations, forming stable, water-soluble 1:1 metal–EDTA complexes whose strict stoichiometry is the basis of the quantitative method. Because the conditional formation constant depends strongly on pH, EDTA titrations are performed in defined buffers with metallochromic indicators — commonly ammonia/ammonium chloride at pH 10 with Eriochrome Black T for total water hardness, and murexide for direct Ca2+ titration in the presence of Mg2+ — and with masking agents to suppress interfering metals. Applications include water-hardness determination, Ca/Mg quantification in pharmaceutical and food matrices, transition-metal analysis, and metal-ion buffers in which a defined free-metal concentration is held constant for kinetic and equilibrium work.

Other Applications

• Chelated iron source (Fe-EDTA) in Murashige–Skoog and other plant tissue-culture and hydroponic growth media
• Metalloprotease and Mg2+/Mn2+-dependent phosphatase inhibition in protease inhibitor cocktails and biochemical sample preparation
• Metal-stripping reagent for IMAC resin regeneration and additive in chromatography buffers where adventitious metal removal is required, excluding active metal-affinity binding steps
• Sequestrant in cosmetic, food-research, and formulation chemistry to limit metal-catalysed oxidation
• Metal-ion masking and metal-ion buffer component in analytical method development and trace-metal speciation studies

Shipping Destinations

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