Sulfuric Acid Digestion (for Phosphate-Based Fertilizers)

• Reagents:Sulfuric acid (H₂SO₄, concentrated, 5–10 mL) Hydrogen peroxide (H₂O₂, 30%, 2–5 mL)
• Procedure:Heat at 200–250°C for 2 hours until a clear solution is obtained. This method works well for phosphate fertilizers but should be avoided for fertilizers containing volatile elements (e.g., As, Hg).

Key Considerations for MP-AES Analysis

• Always filter the digested sample to remove any insoluble residues.
• Ensure consistent acid matrix in standards and samples for accurate MP-AES readings.
• If analyzing silicate-rich fertilizers, use HF (hydrofluoric acid) digestion, but only if your equipment is resistant to HF.

Recommendation: HNO₃ + HCl (Aqua Regia) digestion at 140–160°C is the best method for most fertilizers. If you need to analyze phosphorus-rich samples, H₂SO₄ + H₂O₂ may be more effective.