EDTA(CAS#60-00-4)–Ethylenediaminetetraacetic Acid Chelating Agent

1. Properties:

• Appearance and Physical Form: EDTA is supplied as a white crystalline powder or white monoclinic prismatic crystals, typically with purity ≥99.0% (ACS grade ≥99.4%). The product is odorless and has a slightly acidic taste.
• Solubility: EDTA is sparingly soluble in cold water (0.4–0.5 g/L at 25°C), but solubility increases significantly with temperature (16 g/100 mL at 100°C). It is soluble in alkaline solutions such as sodium hydroxide, sodium carbonate, and ammonia, as well as in dilute mineral acids. EDTA is insoluble in common organic solvents including ethanol, ether, and benzene, making it a hydrophilic chelator that is highly effective in aqueous systems.
• Chemical Properties: EDTA is a hexadentate (six-donor) chelating agent that binds metal ions through its four carboxylate oxygen atoms and two tertiary amine nitrogen atoms, forming extremely stable, water-soluble 1:1 metal-EDTA complexes. It exhibits the highest thermodynamic stability constants for transition metals and alkaline earth metals. The EDTA molecule contains four carboxylic acid groups and two amine groups, acting as a hexaprotic acid (H₆Y²⁺) with pKa values of pK₁=1.70, pK₂=2.60, pK₃=6.30, and pK₄=10.25. It effectively chelates divalent cations such as Ca²⁺, Mg²⁺, Zn²⁺, Cu²⁺, Mn²⁺, and Fe²⁺, as well as trivalent cations including Fe³⁺. EDTA also forms complexes with radionuclides, facilitating their elimination from the body. With a log Kow of -3.34 to -5.01, EDTA is highly hydrophilic and partitions strongly into aqueous phases. The compound decomposes upon heating above 240°C, releasing nitrogen oxides, and may react with strong oxidizing agents. EDTA is readily biodegradable in wastewater treatment systems.

2. Applications:

Industrial & Household Cleaning (Primary):

• Detergents, Soaps & Cleaners: EDTA and its sodium salts are used as sequestering agents (builders) in laundry powders, liquid detergents, dishwashing liquids, and hard surface cleaners. It prevents precipitation of calcium and magnesium salts, improves detergency, enhances foam stability, and removes hard water scale and soap scum residues. EDTA is also used in automatic dishwasher detergents and industrial cleaners to prevent spotting and filming.
• Metal Cleaning & Electroplating: EDTA is employed in metal cleaning formulations and electroplating baths to chelate metal ions, improve bath stability, and enhance deposit quality. It serves as a complexing agent in copper, nickel, zinc, and precious metal plating, controlling free metal ion concentration and improving coating uniformity.

Water Treatment & Boiler Treatment:

• Industrial Water Treatment: EDTA is widely used to sequester hardness ions (calcium and magnesium) in cooling water systems, preventing scale formation on heat exchanger surfaces and piping. It also controls metal ion-catalyzed corrosion.
• Boiler Cleaning: EDTA is used as a detergent for boiler cleaning and descaling, effectively removing iron and calcium deposits from boiler tubes and heat transfer surfaces. Its ability to form stable soluble complexes makes it ideal for removing existing scales without damaging metal substrates.

Pharmaceutical & Medical Applications:

• Chelation Therapy for Heavy Metal Poisoning: EDTA is a first-line treatment for lead, mercury, and other heavy metal poisoning. Administered intravenously as calcium disodium EDTA, it chelates toxic metal ions in the bloodstream, allowing rapid renal excretion. Indications include lead poisoning, arsenic poisoning, aluminum overload, and treatment of iron overload disorders.
• Anticoagulant for Blood Collection: The disodium or tripotassium salts of EDTA are commonly used as an anticoagulant in blood collection tubes (lavender-top tubes) for complete blood count (CBC), hematology, and blood banking procedures. EDTA prevents blood clotting by chelating calcium ions required for coagulation cascade activation. The optimal concentration is 1.5 mg per mL of blood.
• Pharmaceutical Excipient & Vaccine Stabilizer: EDTA acts as a stabilizer in vaccines, ophthalmic solutions, and injectable formulations, preventing metal-catalyzed oxidation of active pharmaceutical ingredients. It is also used as a preservative in some pharmaceutical preparations and as a root conditioning agent in dental treatments.

Food & Beverage Industry:

• Food Preservative (E385): EDTA is approved as a food additive (E385) in many countries, serving as a preservative and antioxidant synergist to prevent oxidative spoilage and discoloration caused by trace metal ions. It is used in canned vegetables, preserved meats, salad dressings, mayonnaise, soft drinks, beer, and fruit juices. EDTA chelates iron, copper, and other transition metals that catalyze fat rancidity, color fading, and off-flavor development, thereby extending shelf life and product quality.

Cosmetics & Personal Care:

• Cosmetic Stabilizer & Sequestering Agent: EDTA is widely used in cosmetic and personal care formulations as a chelating agent to improve product stability and extend shelf life. It prevents metal-catalyzed degradation of fragrances, colors, and active ingredients in shampoos, conditioners, skin creams, lotions, toothpaste, and sunscreens. EDTA also functions as a preservative booster, enhancing the efficacy of traditional preservatives against microbial growth and improving foaming properties in soaps and detergents. The Cosmetic Ingredient Review (CIR) has determined EDTA to be safe for use in cosmetics at concentrations typically ranging from 0.01% to 2.0%.

Agriculture & Horticulture:

• Chelated Micronutrient Fertilizers: EDTA is used to produce water-soluble chelated micronutrient fertilizers (EDTA-Fe, EDTA-Zn, EDTA-Mn, EDTA-Cu) that improve plant uptake of essential trace elements. The EDTA molecule protects metal ions from precipitation and fixation in soil, ensuring controlled release and enhanced bioavailability for crops, ornamental plants, hydroponics, and turf grass.
• Soil Conditioners: EDTA is included in soil amendment formulations to remediate heavy metal-contaminated soils. The chelator binds toxic metals (lead, cadmium, chromium), facilitating their removal through phytoextraction or washing processes, though EDTA is not recommended for phytoremediation due to potential phytotoxicity at higher concentrations.

Textile & Dyeing Industry:

• Textile Dyeing Auxiliary: EDTA is used as a metal ion sequestrant in textile dyeing and printing to improve color brightness, shade consistency, and dye uptake. It prevents heavy metal interference in reactive dyeing processes and improves the whiteness of bleached fabrics.
• Fiber Processing: EDTA is applied in fiber processing to remove metal impurities from raw fibers and to prevent metal-catalyzed degradation during high-temperature dyeing and finishing operations.

Paper & Pulp Industry:

• Bleaching & Whiteness Enhancement: EDTA reduces the adverse effect of metal ions (Fe³⁺, Mn²⁺, Cu²⁺) on peroxide and chlorine dioxide bleaching processes. It promotes whiteness of paper and reduces incrustation in steaming equipment by chelating metal catalysts that decompose bleaching agents prematurely.
• Steamed Fiber Treatment: EDTA is used for treating steamed fiber in papermaking, improving fiber whiteness and preventing scale buildup in digesters and bleaching towers.

High-Molecular Chemical Industry & Polymerization:

• Polymerization Activator & Terminator: EDTA serves as a polymerization activator for butylbenzene latex production and styrene-butadiene rubber (SBR) emulsion polymerization. It is also used as a polyreaction terminator in acrylic fiber production, controlling polymer molecular weight and improving product uniformity.
• Latex Stabilizer: EDTA stabilizes synthetic latex formulations by chelating metal ions that catalyze premature polymerization, ensuring consistent product quality.

Oil & Gas Field Chemicals:

• Oilfield Additives: EDTA is used in oilfield operations as a scale inhibitor, formation cleaning agent, and enhanced oil recovery (EOR) chemical. It removes iron and calcium deposits from wellbores, pipelines, and production equipment, improving flow assurance and equipment longevity. EDTA is also employed in acidizing fluids to prevent precipitation of iron scales and in drilling muds to control metal ion contamination.

Metal Finishing & Metallurgy:

• Electroplating Bath Additive: EDTA is used as a complexing agent in electroplating baths for copper, nickel, zinc, and other metals, controlling free metal ion concentration and improving deposit quality.
• Corrosion Inhibitor: EDTA acts as a corrosion inhibitor to carbon steel in industrial applications by forming a protective film on metal surfaces and sequestering corrosive metal ions.
• Metal Surface Treatment: EDTA is applied in alkaline and acid metal cleaners to remove oxides, scales, and shop soils prior to phosphating, painting, or assembly.

Laboratory & Biochemical Research:

• Enzyme Inhibitor & Metalloprotease Inhibitor: EDTA is used in biochemistry to eliminate trace heavy metal inhibition of enzyme reactions and to inhibit metalloproteases that require divalent cations (Ca²⁺, Zn²⁺, Mg²⁺) as essential cofactors. EDTA chelates the zinc ion at the active site of metalloproteases at effective concentrations of 1–10 mM.
• Molecular Biology Reagent: EDTA is an essential component in molecular biology buffers, including DNA loading dye, resuspension buffer for plasmid isolation, electrophoresis running buffers (TAE, TBE), and cell lysis buffers. It inhibits nucleases and proteases by chelating Mg²⁺, preventing degradation of DNA, RNA, and proteins during extraction and analysis.
• Analytical Chemistry Reagent: EDTA is widely used as a titrant in complexometric titration for the quantitative determination of calcium, magnesium, and total water hardness. It serves as a primary standard for the standardization of metal ion solutions and as a masking agent in trace metal analysis.

Photography & Imaging:

• Photographic Chemical: EDTA is used in photographic processing solutions as a sequestering agent to prevent metal ion precipitation that can cause stains and fog on film and photographic paper.

Rubber & Polymer Industry:

• Rubber Polymerization Additive: EDTA functions as an activator in the emulsion polymerization of styrene-butadiene rubber (SBR) and nitrile rubber (NBR), improving reaction kinetics and polymer properties.

3. Preparation Method:

• Laboratory Method (Munz Synthesis – Historical): The original synthesis developed by Ferdinand Munz involved the reaction of ethylenediamine with monochloroacetic acid in the presence of a base to neutralize the hydrochloric acid formed during the reaction. While groundbreaking, this method was not highly efficient and the final product was often contaminated with sodium chloride.
• Industrial Process (Bersworth Cyanoacetic Acid Method – Current Standard): EDTA is primarily synthesized industrially via the cyanomethylation (also known as the Bersworth process) of ethylenediamine. The process involves the reaction of ethylenediamine (H₂N–CH₂–CH₂–NH₂) with formaldehyde (CH₂O) and sodium cyanide (NaCN) in an aqueous medium. This cyanomethylation yields the tetra-sodium salt of EDTA (Na₄EDTA), which remains dissolved in the reaction mixture. The insoluble EDTA free acid is then precipitated by acidification with hydrochloric acid, followed by filtration, washing, crystallization, and drying. This method is both efficient and cost-effective, forming the basis of modern industrial production. Key quality parameters controlled include purity (≥99.0%–≥99.4%), residue after burning (≤0.15% as SO₄), chloride content (≤0.01%), sulfate content (≤0.1%), iron (≤0.001%), and heavy metals (≤0.001%).

4. Safety Information:

• Hazard Classification: According to GHS and CLP Regulation (EC) No 1272/2008, EDTA is classified with the following hazard statements: H319 (Causes serious eye irritation). H361 (Suspected of damaging fertility or the unborn child). H372 (Causes damage to organs through prolonged or repeated exposure). H332 (Harmful if inhaled, for certain grades). Hazard pictogram: GHS07. Signal word: Danger or Warning (grade dependent).
• Health Hazards: EDTA causes serious eye irritation upon direct contact. Inhalation of dust may cause respiratory tract irritation, coughing, and throat discomfort. Prolonged or repeated exposure may cause damage to organs, particularly the respiratory tract. EDTA is suspected of damaging fertility or the unborn child, with reproductive and developmental toxicity observed in mammals. Cases of pseudothrombocytopenia (EDTA-induced platelet aggregation in blood collection tubes) have been documented, though EDTA remains the standard anticoagulant for hematology testing.
• Personal Protection: When handling EDTA powder, wear appropriate protective equipment including chemical-resistant gloves (nitrile), protective clothing, safety goggles or face shield, and a dust mask (N95 or P2 respirator) to avoid inhalation. Use in well-ventilated areas, preferably a fume hood. Avoid dust formation and aerosol generation.
• First Aid Measures:
  • Eye Contact: Rinse immediately with plenty of water for at least 15 minutes while keeping eyelids open. Remove contact lenses if present and easy to do. Seek medical attention if eye irritation persists.
  • Skin Contact: Wash immediately with plenty of soap and water. Remove contaminated clothing. If skin irritation develops, seek medical advice.
  • Inhalation: Move victim to fresh air. Keep at rest in a position comfortable for breathing. If symptoms (coughing, throat irritation) persist, seek medical advice.
  • Ingestion: Rinse mouth immediately. Do NOT induce vomiting. Seek immediate medical attention. Drink one to two glasses of water if conscious.
• Fire & Explosion Hazards: EDTA is combustible. Finely dispersed EDTA dust particles may form explosive mixtures in air when mixed with air, presenting a dust explosion hazard. In a fire, EDTA gives off irritating or toxic fumes, including nitrogen oxides (NOₓ) and carbon monoxide. Keep containers cool by spraying with water. Use water spray, foam, dry powder, or CO₂ as extinguishing media. Prevent dust deposition; use closed systems and dust-explosion-proof electrical equipment.
• Environmental Precautions: EDTA is readily biodegradable in wastewater treatment systems and has low acute aquatic toxicity. However, large spills should be contained and prevented from entering waterways, sewers, or soil. Avoid direct release into the environment. Comply with local environmental regulations for disposal.
• Storage & Stability: Store in tightly sealed, corrosion-resistant containers (plastic-lined or stainless steel) in a cool (recommended 2–8°C for some grades), dry, well-ventilated area away from direct sunlight, heat sources, and strong oxidizers. Do NOT use aluminum, tin, or zinc containers as EDTA may corrode these metals. Protect from moisture and physical damage. Under recommended storage conditions, EDTA has a shelf life of 12–36 months in original sealed containers.
• Regulatory Compliance: EDTA (CAS#60-00-4, EC#200-449-4) is listed on EINECS, TSCA, DSL, AICS, NZIoC, ENCS, KECI, and other regional chemical inventories. It is approved for use as a food additive (E385) in many countries (FDA 21 CFR §172.135; EU Reg. No. 231/2012), as a pharmaceutical excipient and active ingredient (USP-NF, BP, Ph. Eur.), and as a cosmetic ingredient (CIR approved). EDTA is also listed on the OECD HPV (High Production Volume) Chemicals list. Always consult the Safety Data Sheet (SDS) for complete safety, environmental, and regulatory information specific to each product grade and application jurisdiction.