What is Disodium Phosphate (DSP)? Chemistry, Uses & Safety of Na2HPO4

Disodium phosphate (often abbreviated as DSP in formulation; also called disodium hydrogen phosphate) is a neutral-to-mildly alkaline phosphate salt with the formula Na₂HPO₄. It is widely used because it delivers three “system-control” functions at once: reliable pH buffering (typically in the alkaline range), metal ion sequestration (binding Ca²⁺/Mg²⁺), and protein/dispersion stabilization. These properties make DSP a workhorse ingredient across food (from dairy emulsification to meat texture), pharma/biotech (phosphate buffers), and industrial water systems (scale control support).

Part of Goway’s comprehensive Phosphates Encyclopedia.

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1. DSP at a glance: why it’s a key buffer and stabilizer

In practical formulation, DSP is chosen when you need a predictable pH window and stable performance in the presence of minerals and proteins. It helps keep emulsions and suspensions uniform, reduces the “instability triggers” caused by hard-water ions, and supports consistent processing outcomes.

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2. Chemical properties & product forms (B2B technical core)

2.1 Basic chemistry

• Chemical name: Disodium hydrogen phosphate / Sodium phosphate dibasic
• Formula: Na₂HPO₄ (anhydrous) :contentReference[oaicite:0]{index=0}
• Common hydrates: Na₂HPO₄·7H₂O (heptahydrate), and other hydrates depending on grade/spec
• CAS No.: 7558-79-4 (anhydrous); 7782-85-6 (heptahydrate) :contentReference[oaicite:2]{index=2}
• Molecular weight: 141.96 g/mol (anhydrous); 268.07 g/mol (heptahydrate)
• Appearance: white crystalline powder or granules (varies by hydration and particle spec)
• Alkalinity / pH: typical product specs list pH 8.4–9.6 for a 1% solution (20°C), aligning with its role as a mild alkaline buffer

Hydration matters: anhydrous and low-hydrate forms are often preferred for precision dosing and moisture control, while higher hydrates (e.g., heptahydrate) can be common in industrial supply chains due to handling and cost considerations.

2.2 Grade comparison (typical market structure)

Grade	Typical purity target	Common form	Core uses
Food Grade	≥98% (typical food additive/compendial range)	anhydrous / low-hydrate	dairy & processed cheese emulsification, meat texture/water retention, beverages & dry mix stability
Pharmaceutical / Compendial	tight assay + impurity controls	often anhydrous	phosphate buffers, excipient systems requiring USP/EP-style controls
Industrial Grade	≥95% (typical)	often heptahydrate	water treatment, plating baths, cleaners/detergents, process control

Supplier note (grade discipline): Food/pharma applications must use the correct grade with documented impurity limits and traceability. A representative compendial-quality specification shows controls such as heavy metals (as Pb), fluoride, and other ion limits.

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3. Food-grade DSP: functions & global compliance

3.1 What DSP does in food

• Buffering: helps maintain stable pH in dairy and protein systems, reducing risk of heat/processing-induced protein instability.
• Emulsification support (processed cheese): phosphate salts are widely used to improve melt and emulsification by managing protein-mineral interactions.
• Texture & water-holding (meat systems): supports moisture retention and bite by improving ionic environment and functionality.
• Nutritional phosphorus contribution: contributes phosphate (often used alongside calcium salts depending on formulation goals).

3.2 Regulatory snapshot

Region	Status	Code
United States (FDA)	GRAS (listed in CFR; used per GMP)	21 CFR 182.6290
EU	Authorized food additive within sodium phosphates group	E339(ii) (specifications framework)
JECFA (WHO/FAO)	Evaluated; phosphorus intake guidance is set as a group MTDI	INS 339(ii); Group MTDI 70 mg/kg bw/day (as P)
China (GB)	Permitted under national food additive use standard (latest revision)	GB 2760-2024 (effective 2025-02-08; replaces GB 2760-2014)

Important safety/quality boundary: Food-grade DSP must control impurities (e.g., fluoride and heavy metals) to meet food/compendial expectations; a representative spec lists fluoride limits and heavy metal controls.

Note on phosphate intake: EFSA’s 2019 re-evaluation set a group ADI for phosphates expressed as phosphorus (P) and highlighted that total intake can be a concern in some populations depending on diet patterns.

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4. Pharmaceutical & industrial applications (high-value scenarios)

4.1 Pharma / biotech

• Buffer systems: Na₂HPO₄ is a core component of common phosphate buffer recipes used in labs and bioprocessing.
• Vaccine / biologics manufacturing: “phosphate buffer” appears commonly as an excipient class in vaccine ingredient lists; phosphate buffers typically rely on sodium phosphate salts such as Na₂HPO₄/NaH₂PO₄.

4.2 Industrial

• Boiler/process water: used to support pH control and interact with hardness ions in scale management strategies (always verify local discharge requirements).
• Electroplating baths: can support ionic strength and bath stability in specific formulations.
• Detergents/cleaners: supports water softening/sequestration performance where permitted.

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5. Safety, storage & technical documents

5.1 Safety overview

• Food/compendial use: recognized in major regulatory systems; safety depends on correct grade selection and GMP-level use.
• Industrial handling: avoid dust inhalation and eye contact; standard PPE and ventilation are recommended. SDS notes potential generation of phosphorus oxides under fire conditions.

5.2 Storage

• Keep tightly closed and dry: anhydrous grades can be hygroscopic; hydrates may cake or change flow behavior with humidity.
• Avoid incompatible chemicals: keep away from strong acids and follow SDS guidance for incompatibilities and decomposition products in abnormal conditions.

5.3 Documents to request (Goway can provide by grade)

• COA (assay, pH, P₂O₅ equivalent if applicable, impurity profile)
• SDS (handling, storage, transport, hazard information)
• TDS (particle size, solubility, application notes)
• Compendial statements (e.g., USP/EP/FCC alignment where required)

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6. Conclusion & CTA

Disodium phosphate (Na₂HPO₄) is indispensable because it combines precise buffering, ion control, and stabilization in one ingredient—supporting reliable performance in food processing, compendial buffer systems, and industrial water applications.