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 for divalent- and trivalent-metal-ion control in molecular biology, biochemistry, analytical chemistry, cell culture, and sample preparation. In the fully deprotonated Y⁴⁻ form, its two amine nitrogens and four carboxylates wrap a metal centre into octahedral cage-like complexes with high formation constants (log Kf ≈ 10.7 Ca²⁺, 8.7 Mg²⁺, 16.5 Zn²⁺, 18.8 Cu²⁺, 25 Fe³⁺ at 25 °C, I = 0.1 M). It is a hexaprotic weak acid (H₆Y²⁺ when fully protonated), so the conditional stability constant Kf′ depends strongly on the αY⁴⁻ fraction, making working pH central to every titration and molecular-biology buffer. The free acid is poorly soluble and needs alkaline NaOH or KOH to dissolve at working concentrations; the more soluble disodium-dihydrate and tetrasodium salts allow direct preparation. EDTA binds Ca²⁺ and Mg²⁺ with comparable affinity, so where Ca²⁺-selective chelation is needed alongside physiological Mg²⁺, EGTA is preferred for its much larger Ca²⁺/Mg²⁺ binding-constant differential.

Nucleic-acid protection and enzyme control. EDTA is the standard divalent-cation sequestrant in molecular-biology buffers, suppressing Mg²⁺- and Ca²⁺-dependent enzymes — DNases, divalent-metal-dependent RNases, and metalloproteases — by lowering free metal-ion concentration below their catalytic threshold. It is the EDTA in TE (10 mM Tris-HCl, 1 mM EDTA, pH 8.0) for DNA storage and nuclease-sensitive handling, and in TAE (1×: 40 mM Tris-acetate, 1 mM EDTA, pH ≈ 8.3) and TBE (1×: 89 mM Tris, 89 mM borate, 2 mM EDTA, pH ≈ 8.3) for agarose and polyacrylamide electrophoresis. The same role puts it in stop solutions for restriction digests, ligations, and PCR, and in plasmid- and genomic-DNA lysis buffers and RNA-isolation protocols. It is excluded from active PCR and reverse-transcription mixes, however, because it would sequester the Mg²⁺ cofactor polymerases require.

Cell dissociation and adhesion control. EDTA weakens Ca²⁺- and Mg²⁺-dependent cell adhesion in mammalian culture. Cadherin cell–cell contacts require extracellular Ca²⁺ for homophilic engagement, and integrin cell–substrate interactions depend on Ca²⁺, Mg²⁺, and Mn²⁺ at the metal-ion-dependent adhesion site (MIDAS); sequestering these cations disrupts both adhesion classes at once. Common formulations pair 0.05% or 0.25% trypsin with ~0.5–1 mM EDTA in Ca²⁺/Mg²⁺-free balanced salt solution, letting trypsin reach cleavable peptide bonds once contacts are weakened. Enzyme-free EDTA-in-PBS (typically 0.5–5 mM) serves surface-antigen-sensitive work: flow-cytometry sample preparation, primary-cell dissociation where receptor integrity matters, and stem-cell passaging where trypsin exposure must be minimised.

Hematology anticoagulant and histology decalcification. Dipotassium and tripotassium EDTA (K₂EDTA, K₃EDTA) are the standard anticoagulant additives in lavender-top blood tubes: 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 preferred for these tubes because it minimises the liquid-dilution effect of liquid K₃EDTA. In histology, 10% EDTA buffered to pH 7.4 is the preferred decalcifier for bone, teeth, and other mineralised samples when antigenicity and nucleic-acid integrity must be preserved: it removes calcium phosphate gradually at near-neutral pH, unlike formic, nitric, or hydrochloric acids, leaving protein epitopes and DNA/RNA quality sufficient for immunohistochemistry, in situ hybridisation, and PCR.

Complexometric titration. EDTA is the classical complexometric reagent: its aminopolycarboxylate framework binds almost all di- and trivalent cations as stable, water-soluble 1:1 complexes whose strict stoichiometry is the basis of the method. Because stability is pH-dependent, titrations run in defined buffers with metallochromic indicators — ammonia/ammonium chloride at pH 10 with Eriochrome Black T for total water hardness, murexide for direct Ca²⁺ titration in the presence of Mg²⁺ — and 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 that hold a defined free-metal concentration for kinetic and equilibrium work, including trace-metal speciation and analytical method development.

Further applications.

• Chelated iron source (Fe-EDTA) in Murashige–Skoog and other plant tissue-culture and hydroponic media.
• Metalloprotease and Mg²⁺/Mn²⁺-dependent phosphatase inhibition in protease-inhibitor cocktails and biochemical sample preparation.
• Metal-stripping reagent for IMAC resin regeneration and adventitious-metal removal in chromatography buffers, excluding active metal-affinity steps.
• Sequestrant in cosmetic, food-research, and formulation chemistry to limit metal-catalysed oxidation.

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