3,4-Dimethylpyrazole phosphate (DMPP) (CAS#202842-98-6) – Nitrification Inhibitor for Fertilizers

1. Properties:

• Appearance and Physical Form: DMPP is supplied as a white to off-white crystalline powder. The product is free-flowing, odorless, and exhibits high purity (≥97–98%).
• Solubility: DMPP is soluble in water and methanol. Its water solubility ensures uniform distribution when incorporated into liquid fertilizer formulations or applied to soil.
• Chemical Properties: DMPP is a nitrification inhibitor specifically designed to suppress the activity of Nitrosomonas bacteria in soil, thereby slowing the biological oxidation of ammonium (NH₄⁺) to nitrate (NO₃⁻). By stabilising nitrogen in the ammonium form for a longer period (typically 4–10 weeks), DMPP significantly reduces nitrogen losses through nitrate leaching and denitrification. This unique mechanism maintains nitrogen availability in the root zone, improves nitrogen use efficiency (NUE), reduces fertiliser application frequency, and minimises environmental pollution (e.g., nitrate contamination of groundwater and nitrous oxide emissions). DMPP is non‑phytotoxic, exhibits low acute toxicity, and has been deemed safe by extensive standard toxicology and ecotoxicology tests.

2. Applications:

• Nitrogen Stabilisation in Solid Fertilisers: DMPP is incorporated into granular fertilisers such as urea, ammonium sulfate, calcium ammonium nitrate (CAN), and NPK blends. Typical application rates range from 0.5% to 1.0% of total nitrogen content. It extends the ammonium retention period, maximising the period during which nitrogen remains available for crops.
• Liquid Fertilisers and Slurry: DMPP can be added to liquid fertilisers (UAN – urea ammonium nitrate) and animal slurry (manure). It prevents nitrogen losses during storage and after field application. When mixed with slurry, DMPP effectively suppresses nitrification even in high‑moisture organic environments.
• Enhanced Efficiency Fertilisers (EEFs): DMPP is widely used in premium EEF products, stabilised fertilisers, and controlled‑release nitrogen formulations. It reduces the frequency of fertiliser applications while improving crop yields and quality.
• Sustainable Agriculture: DMPP supports sustainable farming practices by reducing nitrogen leaching into groundwater, decreasing ammonia volatilisation, lowering nitrous oxide (N₂O) emissions (a potent greenhouse gas), and improving overall fertiliser economics.
• Crop‑Specific Recommendations: DMPP is suitable for a wide range of crops including cereals (wheat, maize, rice), vegetables, fruits, and grassland/pasture. It is particularly valuable in regions with high rainfall or irrigated farming where nitrate leaching is a significant concern.

3. Preparation Method:

• Laboratory Method: 3,4-Dimethylpyrazole phosphate is prepared by reacting 3,4-dimethylpyrazole with phosphoric acid under controlled conditions. The reaction proceeds in an aqueous or alcoholic medium at moderate temperatures (50–80°C). The resulting salt is isolated by crystallisation, filtered, washed, and dried to yield the final product.
• Industrial Process: Industrial production follows a straightforward one‑step neutralisation process. 3,4-Dimethylpyrazole is dissolved in a suitable solvent (water or lower alcohol) and neutralised with phosphoric acid (H₃PO₄) at temperatures ranging from 50–90°C. The resulting DMPP is recovered by crystallisation, centrifuged, washed, and dried under reduced pressure. Quality parameters controlled include purity (≥97–98% by HPLC), melting point (167–171°C), residual moisture, and particle size distribution.

4. Safety Information:

• Hazard Classification: DMPP is generally classified as non‑hazardous under GHS/CLP Regulation (EC) No 1272/2008, though it may carry hazard statement H319 (Causes serious eye irritation). Signal word: Warning (depending on grade).
• Health Hazards: DMPP has low acute toxicity. Direct contact with eyes may cause transient irritation. Prolonged skin contact is generally not irritating. Inhalation of dust may cause mild respiratory discomfort. Oral LD50 > 2000 mg/kg (rat).
• First Aid Measures:
  • Eye Contact: Rinse cautiously with water for several minutes. Remove contact lenses if present. Seek medical attention if irritation persists.
  • Skin Contact: Wash with soap and water. Remove contaminated clothing.
  • Inhalation: Move to fresh air. Keep at rest in a position comfortable for breathing.
  • Ingestion: Rinse mouth. Do NOT induce vomiting. Seek medical attention if large amount is ingested.
• Fire & Explosion Hazards: DMPP is not flammable. Thermal decomposition may release phosphorus oxides (POₓ), nitrogen oxides (NOₓ), and carbon oxides. Use water spray, foam, dry powder, or CO₂ as extinguishing media.
• Environmental Precautions: DMPP exhibits low aquatic toxicity. However, avoid direct release into natural water bodies, drains, or soil in large quantities. Comply with local environmental regulations for disposal.
• Storage & Stability: Store in tightly sealed, moisture‑proof containers in a cool, dry, well‑ventilated area away from direct sunlight, heat sources, and strong bases. Shelf life: 24 months in original sealed containers under recommended storage conditions.
• Regulatory Compliance: 3,4-Dimethylpyrazole phosphate (CAS#202842-98-6, EC#2017-001-1) is approved as a nitrification inhibitor in EU fertiliser products (Regulation (EU) 2019/1009) and other global jurisdictions. It is listed on EINECS, TSCA, DSL, and other regional chemical inventories. Always consult the Safety Data Sheet (SDS) for complete safety and regulatory information.