Hyaluronic Acid Free Acid Powder (pH 2.0-3.5, MW <50 kDa) — Low pH HA Supplier
Hyaluronic Acid Free Acid (INCI: Hyaluronic Acid, CAS 9004-61-9, MW <50 kDa, pH 2.0-3.5 at 0.1% w/v) — the protonated, acidic form of HA with reactive -COOH groups. Unlike sodium hyaluronate (pH 5.0-7.0) which buffers acidic formulations toward neutral, the free acid form integrates natively into low-pH systems (pH 3.0-5.5) — chemical peels, AHA/BHA treatments, L-ascorbic acid vitamin C serums (pH 2.5-3.5), and acid-preserved formulations. The low MW (<50 kDa) combined with acidic pH enhancement of stratum corneum permeability achieves deeper epidermal delivery. Convertible to sodium hyaluronate on-demand via simple NaOH neutralization (~0.10 g NaOH per 1.0 g HA) — one inventory, both forms. COSMOS-certified, ISO 9001:2015, c-GMP, HALAL, KOSHER. Low-pH HA manufacturer and bulk supplier — UPOR Biotech.
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Hyaluronic Acid Free Acid Powder (INCI: Hyaluronic Acid, CAS 9004-61-9, MW <50 kDa, pH 2.0-3.5 at 0.1% w/v) is the protonated, acidic form of hyaluronic acid — chemically distinct from the more common sodium hyaluronate salt (NaHA, INCI: Sodium Hyaluronate, CAS 9067-32-7). The key difference: in the free acid form, the D-glucuronic acid carboxyl groups are present as -COOH (protonated, uncharged) rather than -COO⁻Na⁺ (deprotonated, sodium salt). This single chemical difference has profound formulation consequences: (1) pH — 0.1% HA free acid in water produces pH 2.0-3.5 (acidic) vs NaHA at pH 5.0-7.0 (near-neutral). (2) Acid-formulation compatibility — HA free acid integrates natively into low-pH products without the pH drift that occurs when adding NaHA to acidic systems, which buffers toward neutral and can compromise the efficacy of pH-dependent actives (AHAs require pH 3.0-4.0 for optimal free acid penetration; L-ascorbic acid requires pH <3.5 for stability and stratum corneum permeation). (3) Chemical reactivity — the protonated -COOH groups are reactive for esterification, amidation, and other derivatization chemistries, making the free acid the preferred starting material for producing acetylated HA (AcHA), crosslinked HA, and other chemically modified HA derivatives. (4) Convertibility — the free acid can be quantitatively converted to sodium hyaluronate on-demand via simple NaOH neutralization (HA-COOH + NaOH → HA-COONa + H₂O, ~0.10 g NaOH per 1.0 g HA), giving formulators the flexibility of one inventory for both forms. The low MW (<50 kDa) is specifically chosen: at this size, combined with the acidic pH which can transiently enhance stratum corneum permeability via corneodesmosome pH-dependent protease activation and lipid bilayer fluidization, the HA molecules penetrate beyond the skin surface into the viable epidermis and upper dermis — delivering active HA to living tissue rather than remaining as a surface film. UPOR Biotech manufactures this specialty grade under c-GMP and ISO 9001:2015 with COSMOS natural certification.
As a specialized low-pH HA manufacturer and bulk supplier, UPOR Biotech provides the free acid form for cosmetic brands, contract manufacturers, and pharmaceutical developers. OEM formulations available. Free sample for qualified B2B buyers.
Important: Acid Form — Not Sodium Hyaluronate
This is hyaluronic acid (HA) in its native protonated acid form with pH 2.0-3.5 at 0.1% w/v. It is NOT the sodium salt (sodium hyaluronate, NaHA, pH 5.0-7.0). The acid form must be neutralized with NaOH or buffer for neutral-pH cosmetic formulations. It is the premium choice for chemical derivatization (AcHA, crosslinked HA), acidic product environments (AHA/BHA/VC), and brands preferring the native "Hyaluronic Acid" INCI name. Convertible to NaHA on-demand via NaOH neutralization — one inventory, both forms.
Technical Specifications
| Property | Specification |
|---|---|
| Product Name | Hyaluronic Acid Powder — Free Acid Form (Low pH) |
| INCI Name | Hyaluronic Acid |
| CAS Number | 9004-61-9 |
| Chemical Form | Free Acid (protonated -COOH) — NOT sodium salt. Convertible to NaHA via NaOH neutralization. |
| Key Advantage | Acidic HA form — native pH 2.0-3.5 compatible with AHA/BHA/VC formulations. Reactive -COOH for derivatization. Convertible to NaHA on-demand. Low MW <50 kDa for epidermal penetration. |
| Molecular Weight | <50 kDa (GPC-MALLS — low-to-super-low range for deep penetration) |
| Appearance | White to off-white powder; hygroscopic |
| Purity (HPLC-UV 205 nm) | ≥99.0% |
| pH (0.1% w/v Solution, 25°C) — Critical Quality Attribute | 2.0 – 3.5 (confirms free acid form — protonated -COOH groups) |
| pKa (D-Glucuronic Acid Carboxyl) | ~3.0 – 4.0 (typical for HA uronic acid — explains acidic behavior) |
| Glucuronic Acid Content | ≥44.0% (carbazole method — higher than NaHA due to no sodium content) |
| Sodium Content | 0% (free acid — no sodium; distinguishes from NaHA ~5-6% Na) |
| Solution Conductivity (0.1% w/v) | Low (few free ions — protonated -COOH does not dissociate significantly at pH <3.5) |
| Viscosity Building | Low to moderate; pH-dependent (increases upon neutralization as -COO⁻ enables chain expansion) |
| Solubility | Freely soluble in water (slower hydration at low pH; gentle stirring 15-30 min at 25°C or 5-10 min at 40°C) |
| Loss on Drying | ≤10.0% (105°C, 2h) |
| Protein Content | ≤0.1% |
| Heavy Metals (Total) | ≤10 ppm |
| Elemental Impurities | ICH Q3D compliant |
| Microbial Limits | TAMC ≤100 CFU/g; TYMC ≤50 CFU/g (USP <61>); Pathogens — Negative (USP <62>) |
| Formulation Compatibility | Native in pH 3.0-5.5; neutralizable to any pH 3.0-7.0 with NaOH/TEA/arginine; compatible with AHA, BHA, PHA, L-AA, and acid-preserved systems |
| Chemical Derivatization | Reactive -COOH groups — ideal starting material for AcHA, crosslinked HA, and other chemically modified HA derivatives |
| Neutralization — NaOH Stoichiometry | ~0.10 g NaOH per 1.0 g HA (1:1 COOH:NaOH molar ratio); ~2.5 mL of 1M NaOH per 1.0 g HA |
| Recommended Usage | 0.05 – 0.5% w/w for final formulation pH 3.0-5.5 |
| Grade | Cosmetic Grade / Pharma Grade |
| Certifications | ISO 9001:2015, c-GMP, FDA Facility Registration, HALAL, KOSHER, COSMOS Natural Certified, USP/EP compliant |
| Packaging | 1 kg / 5 kg / 25 kg sealed containers with desiccant |
| Storage | 2-8°C recommended; tightly sealed; protect from moisture |
| Shelf Life | 3 years under recommended storage |
Key Benefits — Low pH Hyaluronic Acid
Acid-Formulation Compatible — No pH Drift
The free acid form integrates natively into low-pH systems (3.0-5.5) without causing pH drift. Unlike NaHA which buffers acidic formulations toward neutral — compromising AHA/BHA exfoliation efficacy and vitamin C stability — this grade maintains the acidic environment required by pH-dependent actives and preservatives.
Acid-StableConvertible to NaHA On-Demand — One Inventory, Both Forms
Simple NaOH neutralization (~0.10 g NaOH per 1.0 g HA, 1:1 COOH:NaOH molar ratio) quantitatively converts the free acid to sodium hyaluronate. Titrate to any target pH 3.0-7.0 — giving formulators complete pH control from acidic peels to neutral moisturizers with one raw material.
On-Demand NaHAEnhanced Penetration at Low pH — MW <50 kDa
Low MW (<50 kDa) combined with acidic pH transiently enhances stratum corneum permeability via corneodesmosome protease activation and lipid bilayer fluidization. Achieves deeper epidermal delivery than higher MW or neutral-pH HA — ideal for treatment serums where active penetration is critical.
Deep DeliveryReactive -COOH for Chemical Derivatization
The protonated carboxyl groups are reactive for esterification, amidation, and crosslinking — the preferred starting material for producing AcHA, crosslinked HA, and other chemically modified HA derivatives. NaHA requires a protonation step first, adding complexity.
Derivatization-ReadyApplications
Chemical Peel Serums — Acidic Hydration Without pH Compromise
Core hydrating active in professional and at-home peel formulations at 0.05-0.3%. Delivers HA benefits without buffering the low pH required for acid exfoliation. Compatible with AHA (glycolic, lactic), BHA (salicylic), and PHA systems.
AHA/BHA Treatment Products — Exfoliation-Compatible Hydration
Ideal companion to glycolic, lactic, salicylic, and mandelic acid formulations. Adds deep hydration to exfoliating products without neutralizing the acids' therapeutic pH — the common failure mode when using NaHA in these systems.
Acidic Vitamin C (L-Ascorbic Acid) Serums — pH <3.5 Stability
Perfect HA partner for L-ascorbic acid formulations (target pH 2.5-3.5 for stability and skin penetration). Maintains the low pH required for vitamin C efficacy while delivering anti-irritation hydration at 0.05-0.2%.
Chemical Derivatization — AcHA, Crosslinked HA, and Modified HA
Reactive -COOH groups make the free acid the preferred starting material for esterification (AcHA), divinyl sulfone crosslinking (crosspolymer HA), amidation, and other HA chemical modifications. NaHA requires protonation first.
pH-Optimized Cosmeceuticals — Acid Mantle Support
Key ingredient in cosmeceuticals designed around pH-dependent delivery, skin acid mantle support (pH ~4.5-5.5), and barrier acidification strategies. Enables formulators to target specific pH windows for optimal multi-ingredient performance.
Pharma and Medical Device Gels — Native HA State
Suitable for pharmaceutical gels, wound healing products (acidic wound environment pH 5.5-6.5 during healing), and medical device formulations requiring HA in its native free acid state. USP/EP compliant.
Hyaluronic Acid (HA) vs Sodium Hyaluronate (NaHA) — Complete Comparison
Many formulators use the terms interchangeably — but they are chemically distinct materials with different pH, sodium content, and formulation behavior. This table provides a side-by-side comparison to help select the right form for your product.
| Property | Hyaluronic Acid (HA) — Free Acid | Sodium Hyaluronate (NaHA) — Sodium Salt |
|---|---|---|
| Chemical Name | Hyaluronic Acid (protonated form) | Sodium Hyaluronate (sodium salt) |
| INCI Name | Hyaluronic Acid | Sodium Hyaluronate |
| CAS Number | 9004-61-9 | 9067-32-7 |
| Carboxyl Group State | -COOH (protonated, uncharged) | -COO⁻Na⁺ (deprotonated, sodium salt) |
| pH (0.1% aq. solution) | 2.0 – 3.5 (acidic) | 5.0 – 7.0 (near-neutral) |
| Sodium Content | 0% (no sodium) | ~5-6% sodium by weight |
| Viscosity Building | Low-moderate; pH-dependent (increases upon neutralization) | High; forms viscous gels readily |
| Acid Active Compatibility | Native — no pH drift in AHA/BHA/VC formulas | May buffer acidic formulations toward neutral |
| Chemical Derivatization | Ideal — reactive -COOH groups | Requires protonation step first |
| Skin Penetration (MW-dependent) | Enhanced under acidic pH conditions | Standard; pH-neutral penetration profile |
| Formulation Target pH | 3.0 – 5.5 (or neutralized to higher) | 5.0 – 7.0 |
| Typical Usage Rate | 0.05 – 0.5% | 0.05 – 1.0% |
| Best For | Acidic serums, peels, AHA/BHA/VC, derivatization, acid-preserved systems | General moisturizers, gelled serums, sheet masks, neutral cosmetics |
Conversion Guide — HA (Free Acid) to NaHA (Salt) On-Demand
One key advantage of the free acid form is the ability to produce sodium hyaluronate in situ through controlled neutralization — one inventory, both forms.
The Chemistry and Stoichiometry
HA-COOH + NaOH → HA-COONa + H₂O
NaOH required: ~0.10 g per 1.0 g HA (1:1 molar ratio); ~2.5 mL of 1M NaOH per 1.0 g HA
Step-by-Step Procedure
- Prepare HA Solution: Dissolve HA free acid powder in ~80% of total water. Stir until fully hydrated (15-30 min at 25°C, or 5-10 min at 40°C). Solution will be acidic (pH 2.0-3.5).
- Prepare NaOH Solution: 1M (4% w/w) for lab scale, 10% (w/w) for production. Always add NaOH to water, never the reverse.
- Add NaOH Dropwise with Stirring: Monitor pH after each addition. Solution gradually thickens as the sodium salt forms (-COO⁻ chain expansion) and pH rises.
- Titrate to Target pH: pH 5.5-6.5 for fully neutralized NaHA; pH 5.0-5.5 for skin acid mantle compatible; pH 4.0-5.0 for acid-compatible formulations.
- Add Remaining Water: Once target pH is stable, add remaining water to final volume. Check and adjust pH if needed.
- Proceed with Formulation: The neutralized NaHA solution is ready for incorporation into your formulation.
Molecular Weight Comparison — HA Grades
| Grade | MW | Primary Function | Penetration |
|---|---|---|---|
| High MW | 1,500-2,000 kDa | Film-forming, surface hydration | Surface only |
| HA Low pH <50 kDa (this product) | <50 kDa + pH 2.0-3.5 | Acidic delivery, AHA/BHA/VC compatible, derivatization-ready | Epidermis-Dermis |
| Oligo HA | 7-10 kDa | Cellular signaling, wound healing | Deep dermis |
| Zinc Hyaluronate | 10-50 kDa + Zn 5-8% | Anti-acne, sebum regulation | Epidermis-Dermis |
Frequently Asked Questions
HA free acid has protonated -COOH groups, pH 2.0-3.5 at 0.1% w/v. Sodium hyaluronate (NaHA) has deprotonated -COO⁻Na⁺ groups, pH 5.0-7.0. The free acid integrates natively into acidic products without pH drift — critical for AHA/BHA exfoliation (requires pH 3.0-4.0) and L-ascorbic acid stability (requires pH <3.5). NaHA buffers acidic formulations toward neutral, potentially compromising these pH-dependent actives. The free acid also provides reactive -COOH for chemical derivatization (AcHA, crosslinked HA). Convertible to NaHA on-demand via NaOH neutralization.
Choose low pH HA for acidic products (pH 3.0-5.0): chemical peels, AHA/BHA treatments, L-ascorbic acid serums. Three reasons: (1) No pH drift — maintains acid exfoliation efficacy and vitamin C stability. (2) Reactive -COOH for derivatization — preferred starting material for AcHA, crosslinked HA. (3) Convertibility — one inventory produces both HA and NaHA via simple NaOH titration. For general-purpose neutral-pH moisturizers, standard NaHA may be simpler. For acidic treatment products requiring precise pH control, the free acid is the correct choice.
MW <50 kDa — low-to-super-low range. At this size, HA molecules penetrate beyond the skin surface into the viable epidermis and upper dermis. Combined with low pH (2.0-3.5) which transiently enhances stratum corneum permeability via activation of corneodesmosome-degrading proteases (kallikrein-related peptidases KLK5/KLK7) and lipid bilayer fluidization, this grade achieves deeper active HA delivery than higher MW or neutral-pH forms. For acidic treatment serums where ingredient penetration is the primary goal rather than surface film-forming.
ISO 9001:2015, c-GMP, FDA-registered, HALAL, KOSHER, COSMOS Natural Certified. Meets USP and EP pharmacopoeia standards. Every shipment: COA (pH 2.0-3.5, MW <50 kDa, purity ≥99.0%, glucuronic acid ≥44.0%, sodium content 0%), MSDS, TSE/BSE statement, stability data, complete lot traceability.
0.05-0.5% for final formulation pH 3.0-5.5. Two approaches: (1) Use as-is for fully acidic systems (peels, low-pH serums) where the natural pH 2.0-3.5 is an asset. (2) Partially neutralize with NaOH, TEA, or arginine to any target pH 3.0-7.0. Neutralization: ~0.10 g NaOH per 1.0 g HA (~2.5 mL of 1M NaOH per 1.0 g HA). Titrate dropwise to target: pH 5.5-6.5 (fully neutralized NaHA), pH 5.0-5.5 (acid mantle compatible), pH 4.0-5.0 (for acid-compatible formulations). Dissolves freely in water; compatible with most water-phase ingredients.