Chemical Identity and Properties

Ethylenediaminetetraacetic Acid Lead(II) Disodium Salt Hydrate (SKU E156499) is a coordination compound formed by the chelation of lead(II) ions (Pb²⁺) with the hexadentate ligand ethylenediaminetetraacetate (EDTA⁴⁻). Two sodium counter-ions and one or more waters of crystallization complete the salt hydrate structure.

EDTA is one of the most widely used chelating agents in analytical and coordination chemistry, capable of forming thermodynamically stable 1:1 metal–ligand complexes with most divalent and trivalent metal ions. In the Pb–EDTA complex, the ligand coordinates through its two amine nitrogen atoms and up to four carboxylate oxygen atoms, encapsulating the Pb²⁺ centre and greatly reducing its free-ion activity in solution.

Key physicochemical characteristics include:

• Solubility: Freely soluble in water; solutions are clear and colorless to pale yellow. Insoluble in common organic solvents.
• Stability: The Pb–EDTA chelate is thermodynamically stable across a wide pH range (approximately pH 4–12), minimising hydrolysis or precipitation of lead hydroxide under typical laboratory conditions.
• Stoichiometry: 1:1 Pb:EDTA molar ratio; the disodium salt form ensures defined ionic composition suitable for gravimetric or volumetric preparation of standard solutions.

Because the lead content is fixed by the stoichiometric formula, this reagent allows straightforward calculation of lead concentration in prepared solutions, which is critical for calibration and method validation work.

Preparation of Standard Solutions

Accurate preparation of Pb–EDTA solutions is essential for reliable analytical results. Follow the procedure below as a general guideline; adapt volumes and concentrations to your specific protocol.

Materials Required

• Ethylenediaminetetraacetic Acid Lead(II) Disodium Salt Hydrate (E156499)
• Ultrapure (Type 1) water, freshly prepared
• Calibrated analytical balance (readability ≤ 0.1 mg)
• Class A volumetric glassware
• pH meter
• Inert storage containers (HDPE or glass; avoid uncoated metal)

General Procedure

1. Dry if required: If the degree of hydration must be precisely known, dry a portion of the reagent at a temperature appropriate for the hydrate form and weigh after equilibration. Consult the certificate of analysis (CoA) for guidance on water content.
2. Weigh accurately: Transfer the required mass of E156499 to a tared beaker or volumetric flask. Calculate mass using the molecular weight stated on the CoA, accounting for water of crystallization.
3. Dissolve: Add approximately 70–80% of the final volume of ultrapure water and stir gently until completely dissolved. Avoid vigorous agitation that could introduce atmospheric CO₂ and alter pH.
4. Adjust pH (if needed): For applications requiring a specific pH, adjust with dilute sodium hydroxide or dilute nitric acid (trace-metal grade). EDTA solubility and complex stability are both pH-dependent.
5. Make to volume: Transfer quantitatively to a volumetric flask and dilute to the mark with ultrapure water. Mix by repeated inversion.
6. Label and store: Label with reagent name, lot number, concentration, preparation date, and preparer's initials. Store in HDPE or borosilicate glass bottles at 2–8 °C, away from light.

Note: Because lead is a toxic heavy metal, all solution preparation steps should be performed in a designated fume hood or ventilated enclosure with appropriate personal protective equipment (PPE).

Analytical Applications

The well-defined stoichiometry and high stability of the Pb–EDTA chelate make Ethylenediaminetetraacetic Acid Lead(II) Disodium Salt Hydrate suitable for a range of analytical and research applications:

1. Calibration Standards for Lead Analysis

Because the Pb:EDTA ratio is fixed at 1:1 and the compound is available as a pure, characterized solid, it can serve as a primary or secondary calibration standard for atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and anodic stripping voltammetry (ASV). Researchers preparing matrix-matched standards benefit from knowing that the lead is present in a fully complexed, non-ionic form, which may be important for method development involving speciation or matrix-spike recovery studies.

2. Heavy Metal Speciation Studies

Environmental and toxicological research increasingly distinguishes between free ionic lead and organically or inorganically complexed lead, since bioavailability and toxicity differ markedly between species. Pb–EDTA serves as a model Pb-organic-complex reference material to validate speciation methods including size-exclusion chromatography (SEC), capillary electrophoresis (CE), and hyphenated ICP-MS techniques.

3. Coordination Chemistry and Mechanistic Studies

The compound is used as a well-characterized starting material or reference complex in studies probing metal–ligand exchange kinetics, transmetallation reactions, and the thermodynamics of EDTA complexation with heavy metals. Its high formation constant (log K for Pb–EDTA reported in coordination chemistry literature) provides a useful benchmark for comparing competing chelators in development of new chelation therapy agents or environmental remediation ligands.

4. Quality Control and Proficiency Testing

Certified or characterised Pb–EDTA solutions can be included as blind QC samples within a laboratory's internal quality management system to assess instrument drift, analyst bias, and method robustness over time.

Safety, Handling, and Storage

Lead and all its compounds are classified as toxic and hazardous to health and the environment. Although chelation by EDTA substantially reduces the free-ion activity of Pb²⁺ in solution, the compound must still be treated as a lead-containing hazardous material. Researchers must consult the Safety Data Sheet (SDS) for E156499 before use and comply with all applicable local, national, and institutional regulations for the handling, storage, and disposal of lead compounds.

Personal Protective Equipment (PPE)

• Nitrile or neoprene gloves; double-gloving recommended when handling concentrated solutions or dry powder.
• Laboratory coat and long trousers; closed-toe shoes.
• Safety glasses or chemical splash goggles.
• Work in a fume hood when weighing powders or preparing concentrated solutions.

Handling Precautions

• Avoid generating dust when handling the solid form; weigh inside a ventilated enclosure.
• Do not eat, drink, or smoke in the laboratory area where lead reagents are used.
• Wash hands and forearms thoroughly with soap and water immediately after use.
• Decontaminate spills immediately: collect solid residue and absorb liquid with inert absorbent material; dispose of as hazardous waste.

Storage Conditions

• Store in a cool (2–25 °C), dry, well-ventilated location, away from incompatible materials (strong oxidisers, strong acids).
• Keep containers tightly sealed when not in use to prevent moisture uptake and contamination.
• Store separately from food-grade materials and away from areas accessible to non-laboratory personnel.

Waste Disposal

All lead-containing waste solutions, contaminated glassware rinses, and solid residues must be collected in designated, labelled heavy-metal waste containers and disposed of according to institutional Environmental Health and Safety (EHS) guidelines and applicable regulations. Do NOT pour lead waste down the drain.

Quality Assurance and Regulatory Considerations

When using Ethylenediaminetetraacetic Acid Lead(II) Disodium Salt Hydrate (E156499) as a reference or calibration material, the following quality assurance practices are recommended:

Certificate of Analysis (CoA)

Always obtain and retain the batch-specific CoA for E156499. Verify the reported purity, water content (hydrate factor), and any spectroscopic or elemental analysis data before use. The CoA is essential documentation for GLP and ISO 17025 accredited laboratories.

Traceability

For regulated analytical methods (e.g., environmental monitoring, clinical or food-safety testing), verify whether the calibration standard requires traceability to a national metrology institute (NMI) such as NIST, PTB, or equivalent. If certified reference material (CRM) status is required, consult Aladdin Scientific's technical support team regarding available options.

Shelf Life and Re-testing

Observe the expiry or re-test date on the label. Hygroscopic uptake by the hydrate can alter the effective lead concentration of solutions prepared from aged material. If the material has been stored beyond its stated validity period, re-characterisation by an independent method (e.g., ICP-OES or titration against a traceable EDTA standard) is recommended before use in critical applications.

Regulatory Compliance

Lead compounds are subject to regulatory controls in many jurisdictions (e.g., RoHS, REACH, EPA regulations for lead in water). Researchers are responsible for ensuring that use, transport, and disposal of E156499 comply with all applicable regulations. Contact your institution's EHS office for jurisdiction-specific guidance.