Cadmium (Cd) is primarily present as Cd²⁺ ions.

Alternative Methods for Cadmium Analysis

• Atomic Absorption Spectroscopy (AAS): High sensitivity and accuracy.
• Inductively Coupled Plasma Mass Spectrometry (ICP-MS): Very precise for trace analysis.
• Spectrophotometry with Dithizone: Color development through complex formation.
• Complexometric Titration with EDTA: Suitable for the quantitative determination of Cd²⁺.

Titration of Cadmium with EDTA

1. Principle of the Method

Cadmium ions (Cd²⁺) form a stable complex with Ethylenediaminetetraacetic Acid (EDTA, C₁₀H₁₆N₂O₈):

The endpoint is detected using Eriochrome Black T as an indicator (color change from wine red to blue).

2. Chemicals

• 0.01 mol/L EDTA solution (C₁₀H₁₆N₂O₈)
• Buffer solution (pH 10, NH₃/NH₄⁺ buffer)
• Eriochrome Black T (indicator)

3. Experimental Setup

Required Equipment:

• Burette (25 mL, 0.1 mL graduations)
• Erlenmeyer flask (250 mL)
• Pipette (10 mL)
• Magnetic stirrer

4. Procedure

1. Add 10 mL of the nutrient solution to a 250-mL Erlenmeyer flask.
2. Add 10 mL of buffer solution (pH 10).
3. Add 2-3 drops of Eriochrome Black T indicator.
4. Titrate with 0.01 mol/L EDTA until the color changes from wine red to blue.

5. Calculation of Cadmium Concentration

The Cd concentration is calculated using the formula:

6. Example Calculation

• EDTA concentration: 0.01 mol/L
• Volume used: 9.2 mL (0.0092 L)
• Sample volume: 50 mL (0.050 L)

Conclusion

The complexometric titration with EDTA is a precise method for the quantitative determination of cadmium in nutrient solutions. For more accurate trace analysis, AAS or ICP-MS is recommended.

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