EDTA-2Na vs. EDTA-4Na: Key Differences

EDTA (Ethylenediaminetetraacetic acid) is a widely used chelating agent. Its sodium salts (EDTA-2Na and EDTA-4Na) differ in sodium content, solubility, and application suitability.

1. Chemical Structure & Properties

Property	EDTA-2Na	EDTA-4Na
Full Name	Disodium EDTA	Tetrasodium EDTA
Formula	C₁₀H₁₄N₂Na₂O₈·2H₂O	C₁₀H₁₂N₂Na₄O₈·4H₂O
CAS No.	6381-92-6	64-02-8
Sodium Ions	2	4
pH (1% Solution)	4.0–5.5 (weakly acidic)	10.5–11.5 (alkaline)
Solubility in Water	~100 g/L (requires warm water)	~200 g/L (readily dissolves in cold water)

2. Functional Differences

Aspect	EDTA-2Na	EDTA-4Na
Chelation Efficiency	Effective in acidic to neutral pH	Optimal in alkaline conditions (pH 8–12)
Metal Ion Binding	Prefers Ca²⁺, Mg²⁺, Fe²⁺ in low pH	Stronger binding in high pH (e.g., Fe³⁺)
Stability	Less stable in alkaline solutions	Stable in alkaline environments

3. Applications

Field	EDTA-2Na	EDTA-4Na
Food Industry	Acidic foods (e.g., canned fruits, soft drinks)	Neutral/alkaline foods (e.g., dairy, baked goods)
Cosmetics	pH-sensitive formulations (creams, lotions)	Shampoos, soaps (alkaline systems)
Pharmaceuticals	Blood anticoagulants (neutral pH)	Stabilizer for alkaline drug solutions
Water Treatment	Acidic water systems (e.g., boiler feed)	Alkaline cooling towers, detergents
Laboratory Use	DNA/RNA buffers (neutral pH)	Protein purification (high pH buffers)

4. Cost & Handling

Factor	EDTA-2Na	EDTA-4Na
Cost	Lower (simpler synthesis)	Higher (additional sodium ions)
Storage	Store in dry, cool conditions	Hygroscopic; requires airtight storage
Safety	Mild skin/eye irritation	Similar irritation risk; higher alkalinity

5. Regulatory Notes

Food Grade:
- EDTA-2Na: Approved as E386 in EU, limited to 75 mg/kg in beverages.
- EDTA-4Na: Less common in food; used in detergents (e.g., EU Ecolabel compliant).
Industrial Use: Both comply with REACH and ISO standards.

When to Choose Which?

EDTA-2Na:
- Acidic or neutral pH systems (pH 4–7).
- Cost-sensitive applications (e.g., food preservation).
- Low sodium content required.
EDTA-4Na:
- Alkaline environments (pH >8).
- High solubility needed without heating.
- Detergent formulations or hard water scaling prevention.

Key Takeaway:
EDTA-2Na and EDTA-4Na are complementary. Select based on pH requirements, solubility needs, and cost constraints. Always verify compatibility with your system’s chemistry!