| HS Code | 587465 |
| Chemical Name | Silicon Dioxide (Colloidal Silicon Dioxide / Fumed Silica, Aerosil Pharma Grade) |
| Cas Registry Number | 7631-86-9 |
| Molecular Formula | SiO2 |
| Molecular Weight | 60.08 g/mol |
| Appearance | White, light, fluffy, free-flowing amorphous powder |
| Solubility | Practically insoluble in water and organic solvents; soluble in hot concentrated alkali and hydrofluoric acid |
| Specific Surface Area | 200 ± 25 m2/g by BET method |
| Ph | 3.7 to 4.7 in 4% aqueous dispersion |
| Tapped Density | Approximately 90 g/L |
| Primary Particle Size | Approximately 12 nm, typically aggregated into micron-sized clusters |
As an accredited Silicon Dioxide/Aerosil Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sealed double-lined polyethylene bags inside fiber drums, tamper-evident, labeled. Net weight: 25 kg per drum. |
| Container Loading (20′ FCL) | 20′ FCL container loading of Silicon Dioxide/Aerosil Pharma Grade API, securely packed for oral/injectable use, ensuring contamination-free transport. |
| Shipping | Silicon Dioxide/Aerosil Pharma Grade API ships in sealed, moisture-resistant containers to preserve purity. Transport via dry, temperature-controlled freight, protected from contamination. Labeled for pharmaceutical use; comply with IATA/IMDG for injectable grades. Proper documentation, traceability, and GMP handling ensure safe delivery for oral and injectable applications. |
| Storage | Store in a tightly closed original container in a cool, dry, well-ventilated area, away from direct heat and moisture. Protect from high humidity and ensure the container is resealed immediately after use. Avoid dust generation and contact with incompatible materials. Use appropriate personal protective equipment when handling. |
| Shelf Life | Shelf life is 36 months when stored in original, tightly closed container at room temperature, protected from moisture and contamination. |
In automatic capsule filling equipment, colloidal silicon dioxide with BET 200 m²/g is used to control powder-plug friction, reduce sticking to dosator pins, and improve fill weight uniformity for low-density cohesive formulations. The addition ratio is typically 0.15–0.75 wt% of the final fill formulation; hydrophobic APIs with high surface free energy may require 0.50–1.00 wt%, but fill weight variability can increase above 1.00 wt% because the silica's low tapped density of approximately 50 g/L reduces plug cohesion in dosator chambers. Production-scale filling lines with dosator machines operate with powder bed heights of 30–60 mm and compression pin loads of 50–150 N; tamping-pin lines use 5–12 tamping stations and precompression loads of 20–80 N depending on pin diameter. The characteristic failure mode on automatic capsule fillers is a drift in net fill weight when silica is not adequately dispersed; this appears as a ring-shaped residue on dosator pins and requires line clearance within 2–4 h of continuous operation. Weight uniformity is monitored by USP 905 and Ph. Eur. 2.9.5; powder flow is characterized by USP 1174 or Ph. Eur. 2.9.36. The process constraint is that silica must be blended for 5–10 min after passing through an 800 μm mesh; longer blending can cause electrostatic adsorption of silica onto the gelatin or HPMC shell surface during capsule opening and filling. Terminal product types include hard gelatin capsules, HPMC capsules, and powder-in-capsule formulations for immediate-release oral administration. For moisture-sensitive compounds, the higher surface area 300 m²/g grade may be used at 0.10–0.30 wt% to scavenge free moisture during encapsulation rather than to lubricate plug flow.
High-shear and fluid-bed granulation lines use colloidal silicon dioxide at two deliberately separated points: an intragranular addition of 0.10–0.50 wt% of the dry powder charge before binder solution delivery, and an extragranular addition of 0.25–1.00 wt% after the dried granules are milled. The intragranular portion acts as a moisture scavenger on the surface of hydrophilic APIs and reduces overwetting during binder addition; the extragranular portion controls the flow of milled granules into sachet fillers, tablet presses, or capsule dosators. On a high-shear granulator of 600 L working capacity, main impeller speeds of 120–180 rpm and chopper speeds of 1200–1800 rpm are used; binder solution pump rates are adjusted to maintain a wet mass torque rise of 20–40% above the dry-mix baseline. After wet massing, the granules are dried in a fluid-bed dryer with inlet air at 50–70°C until loss on drying reaches 1.5–2.5%, then milled through a conical mill fitted with a 0.8–1.0 mm round-hole screen. Extragranular silica is then blended with the milled granules in a diffusion mixer for 5–10 min at 10–15 rpm. The key processing boundary is that intragranular silica above 1.5 wt% can reduce granule tensile strength by obstructing liquid bridges during granule growth, while extragranular silica above 1.0 wt% can decrease tablet hardness after compression and may generate dust in high-speed tablet presses. Granule flow is measured by USP 1174 and Ph. Eur. 2.9.36, with a Carr index below 20 and angle of repose below 35° considered suitable for automatic feeding equipment. Terminal product types include granules for oral solution, sachet granules, dry syrup powders, and intermediate granulations for tablet compression or capsule filling. Compliance is anchored to ICH Q3D element-specific limits, ICH Q3C residual solvent requirements, and 21 CFR 211.110 in-process sampling and testing.
| Application track | Typical addition ratio | Standards / test methods | Process-specific limit |
|---|---|---|---|
| Direct compression tablet flow control | 0.10–0.50 wt%; up to 1.00 wt% for cohesive APIs | USP 1174; Ph. Eur. 2.9.36; ICH Q3D | Blending beyond 30 min may induce silica migration and segregation. |
| Capsule powder plug filling | 0.15–0.75 wt% | USP 905; Ph. Eur. 2.9.5 | Above 1.00 wt% may reduce plug cohesion and increase fill weight RSD. |
| Wet granulation (intra/extra) | Intra 0.10–0.50 wt%; extra 0.25–1.00 wt% | USP 1174; Ph. Eur. 2.9.36; 21 CFR 211.110 | Intragranular above 1.5 wt% reduces granule tensile strength. |
| Oral suspension viscosity/yield stress | 0.5–3.0 wt% | USP 912; Ph. Eur. 2.2.10; Ph. Eur. 5.1.4 | pH above 9.0 progressively weakens silanol network. |
| Injectable suspension rheology | 0.05–0.50 wt% | USP 71, 85, 788; Ph. Eur. 5.1.1 | Terminal sterilization at 121°C for 15 min requires pre-validated aggregate control. |
| Effervescent granule anti-caking | 0.10–0.50 wt% | USP 701; Ph. Eur. 2.9.1 | Environmental RH above 25% causes premature acid-base reaction. |
Because fumed silica is practically insoluble and cannot be sterile-filtered, colloidal silicon dioxide in injectable suspension manufacturing is evaluated as a rheology-modifying suspending agent for sterile aqueous suspensions that require terminal moist-heat sterilization. The addition ratio is generally restricted to 0.05–0.50 wt% of the aqueous phase; at higher loadings, the increase in dynamic viscosity can exceed the acceptable syringeability limit and the suspension may fail the USP 788 particulate matter test after autoclaving if aggregates are not fully dispersed. The manufacturing route uses either aseptic addition of depyrogenated silica to a sterile vehicle or aseptic filtration of the vehicle components followed by terminal steam sterilization of the final container at 121°C for 15 min in validated load configurations to achieve an F0 value of not less than 8. High-pressure homogenization at 500–1,500 bar is typically required after rotor-stator dispersion to reduce silica agglomerates to sub-visible size; the homogenizer contacting surfaces are cleaned under 21 CFR 211.67 and sterilized by clean-in-place steam cycles. Laser diffraction under USP 429 is used to track agglomerate reduction; if the D50 remains above 30 μm after high-pressure homogenization, additional passes are required before terminal sterilization. Critical release specifications include bacterial endotoxin under USP 85, sterility under USP 71, and sub-visible particle counts under USP 788 or Ph. Eur. 2.9.19. The operational incompatibility is that silica can adsorb protein-derived active substances and reduce potency; for peptide or protein injectables, published data for this specific configuration is limited, and comparability studies are mandatory before commercial use. Terminal product types include sterile suspension for intramuscular or subcutaneous injection, injectable depot suspensions, and aqueous injectable vehicles where controlled flocculation is desired. The excipient for injectable use must be supported by endotoxin data and should be produced under IPEC-PQG excipient GMP with a bacterial endotoxin specification aligned to the finished-product limit; if a manufacturer does not provide an injectable-grade certificate of analysis, the material is not suitable for this route.
In effervescent granule manufacture using anhydrous citric acid and sodium bicarbonate, colloidal silicon dioxide is added as an external-phase anti-caking agent to maintain granule flow in packaging areas where residual moisture initiates premature acid-base reaction. The addition ratio is 0.10–0.50 wt% of the finished granule; at 0.50 wt%, silica reduces interparticulate caking without delaying tablet disintegration or leaving an insoluble film on the dissolution vessel. The granules are dried in a fluid-bed dryer at inlet air temperature not exceeding 60°C to a final water content below 0.5% as measured by Karl Fischer titration under USP 921. After drying and sizing through a 1.0 mm screen, the silica is blended in a low-shear diffusion mixer for 5–8 min; longer blending can increase dust and create flow irregularity in the compression hopper. Process rooms are maintained at 20–25% relative humidity and 18–22°C to prevent surface hydration of the acid and carbonate particles before compression. On rotary presses, compression forces are typically 12–20 kN, and the feed frame speed is limited to 30–50 rpm to avoid overworking the blend and generating static charge. Disintegration time is controlled by USP 701 and Ph. Eur. 2.9.1 disintegration testing; the target is less than 5 min in water at 15–25°C. Terminal product types include effervescent tablets, effervescent granules for single-dose sachets, and granules for carbonated oral solutions. The primary process boundary is that silica does not replace low-humidity environmental control; if package moisture ingress exceeds the container closure system's qualified moisture vapor transmission rate measured by USP 671, effervescent stability may be compromised even with optimized silica addition.Competitive Silicon Dioxide/Aerosil Pharma Grade API for Tablet / Capsule / Granule / Injection, Oral & Injectable prices that fit your budget—flexible terms and customized quotes for every order.
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Silicon Dioxide/Aerosil Pharma Grade API is colloidal anhydrous silica controlled under Ph. Eur. 0434 and USP-NF Colloidal Silicon Dioxide. The product is manufactured by flame hydrolysis of silicon tetrachloride; the resulting amorphous, chain-like aggregates consist of fused primary particles with surface silanol groups and siloxane bonds. The hydrophilic grades Aerosil 200 Pharma and Aerosil 300 Pharma are specified by specific surface area, pH of aqueous dispersion, loss on drying, silica content, heavy metals, and microbial quality. Regulatory classification places colloidal silicon dioxide as an excipient, not an active pharmaceutical ingredient; the trade designation “API grade” denotes compendial purity and low bioburden suitable for excipient use in oral and injectable dosage form manufacture.
In direct compression, the low tap density and high external surface area allow the silica to coat tablet excipient particles at low addition levels, reducing electrostatic charging and powder-wall adhesion. The same surface structure that improves flow also adsorbs moisture and liquid binders, which is exploited in wet and dry granulation. The low bulk density creates dusting during uncontained transfer; production-scale handling therefore requires vacuum conveying with HEPA-filtered exhaust and a charging hopper equipped with a split-cone valve to limit segregation. Batch-to-batch variance in die filling on rotary tablet presses has been observed when silica is added directly to the final blend without pre-mixing. A pre-blend of silica with a portion of filler at 1:10 ratio for 5 min before addition to the main blender reduces local agglomerates and improves flow homogeneity.
Fumed silica differs from precipitated silica in aggregation mechanism, tap density, external surface area, and trace impurity profile. The flame hydrolysis route produces branched, three-dimensional aggregates of non-porous primary particles; Aerosil 200 Pharma has a typical tapped density near 50 g/L, while precipitated silica grades usually have higher settled densities and a porous, irregular structure. The controlled BET surface area for hydrophilic pharma grades is 200 ± 25 m²/g for Aerosil 200 Pharma and 300 ± 30 m²/g for Aerosil 300 Pharma. Precipitated grades do not normally achieve this external surface area at equivalent purity. Fumed pharma grades also carry lower residual electrolytes and meet tighter elemental impurity limits under ICH Q3D when evaluated in the finished drug product.
Compared with talc, fumed silica provides flow regulation at lower concentration because its external surface area is larger per unit mass; talc is a lamellar magnesium silicate and contributes higher residue on ignition. Compared with magnesium stearate, silica is not a boundary lubricant and does not produce the hydrophobic compression ejection effect; therefore silica does not replace magnesium stearate in tablet formulations. Compared with microcrystalline cellulose, colloidal silicon dioxide has no plastic deformation under compaction and does not contribute to tablet tensile strength.
Specific surface area is determined by nitrogen adsorption using the BET method. Loss on drying is determined at 105°C for 2 h in accordance with the compendial procedure. Table 1 compiles typical manufacturer data for the two hydrophilic grades most frequently used in oral solid dosage forms.
| Parameter | Aerosil 200 Pharma | Aerosil 300 Pharma |
|---|---|---|
| Specific surface area (BET) | 200 ± 25 m²/g | 300 ± 30 m²/g |
| pH, 4% aqueous dispersion | 3.7–4.5 | 3.7–4.5 |
| Loss on drying, 105°C for 2 h | ≤2.5% | ≤2.5% |
| Silica content, ignited basis | ≥99.8% | ≥99.8% |
| Typical tapped density | approx. 50 g/L | approx. 50 g/L |
Primary particle size for Aerosil 200 Pharma is approximately 12 nm; for Aerosil 300 Pharma it is approximately 7 nm. These values are derived from manufacturer technical data and are not applied as release specifications. Specific surface area correlates inversely with primary particle size; the smaller primary particle size of Aerosil 300 Pharma produces a more branched aggregate with higher oil absorption. The higher specific surface area increases the number of accessible silanol groups per unit mass, producing stronger hydrogen-bonding interactions with adsorbed water and higher thickening efficiency in non-aqueous systems. Aerosil 200 Pharma is often preferred for routine tablet flow regulation because the lower surface area reduces the risk of over-structuring and permits a wider granulation endpoint window in high-shear wet granulation.
In tablet and capsule manufacturing, Aerosil 200 Pharma is typically added at 0.1–1.0 wt% of the total powder mass. At this level, the product reduces interparticulate friction, improves powder flow through die feed frames, and prevents rat-holing in the hopper. For moisture-sensitive actives, use at 1–3 wt% as an adsorbent converts liquid binders or oily additives into free-flowing granules; above 5 wt%, compact hardness may decrease because silica aggregates interrupt binder-particle contact. The material is practically insoluble in water and organic solvents, so it remains dispersed in the tablet matrix and does not contribute significantly to dissolution value at typical use levels. Flow function coefficient measured by annular shear cell generally improves only when the host powder is poor-flowing; for free-flowing powders with a flow function coefficient above 10, the incremental benefit is negligible.
In dry granulation by roller compaction, silica is added before the powder enters the nip region at 0.2–0.5 wt% to prevent sticking to rolls and improve feed uniformity. In melt granulation with PEG or fatty acid binders, hydrophilic silica at 1–2 wt% increases the viscosity of the molten binder and prevents binder migration to the granule surface; published data for this specific configuration is limited and endpoint determination should use torque rather than fixed time.
In high-shear wet granulation, silica is admixed with the dry phase before binder solution is sprayed. The dispersed silica adsorbs excess granulation liquid and extends the endpoint range by reducing overwetting at a given impeller power draw. On a laboratory-scale high-shear mixer with a chopper speed of 1,500 rpm and impeller speed of 150 rpm, 0.5 wt% Aerosil 200 Pharma reduces granule size variability, but the exact endpoint depends on bowl geometry and binder viscosity. In tablet formulations containing high-dose hygroscopic actives, intragranular addition of silica at 0.5–1.0 wt% before wet massing reduces moisture-induced agglomeration and improves final granule size distribution after drying. Extragranular addition at 0.25–0.5 wt% after sieving improves flow without altering compact hardness; when both intragranular and extragranular silica are used, the total level should remain below 3 wt% to avoid compression hardening and loss of tablet tensile strength.
In capsule filling of low-dose actives, the anti-caking action maintains uniform drug distribution under storage conditions up to 40°C/75% RH when the primary packaging provides an adequate moisture barrier. During processing at relative humidity above 60%, pre-drying of the silica at 105°C for 2 h is required because the large surface area adsorbs atmospheric moisture and can increase loss on drying beyond 2.5%.
In parenteral suspensions, colloidal silicon dioxide is dispersed under high shear to create a three-dimensional network that slows sedimentation and prevents compacted sediment. The injectable grade is tested for bacterial endotoxins according to Ph. Eur. 2.6.14 or USP <85>, and for total aerobic microbial count and specified objectionable organisms according to Ph. Eur. 5.1.4 or USP <61> and <62>. Sterile filtration is not generally applicable because the dispersed silica aggregates are retained; terminal sterilization by autoclaving at 121°C for 15 min is the standard method where the formulation permits. The hydrophilic grade is required for aqueous wetting; hydrophobic Aerosil R972 Pharma is not a direct substitute in aqueous injectable suspensions because the methylated surface prevents uniform dispersion without surfactant addition.
Parenteral suspensions using colloidal silicon dioxide are usually flocculated rather than deflocculated; the silica network creates weak particle-particle flocs that settle rapidly but redisperse easily. This differs from polymeric stabilizers such as povidone or carbomer, which increase continuous-phase viscosity. Stability is pH-dependent because surface silanol ionization changes zeta potential; maximum flocculation often occurs near the isoelectric point of silica around pH 2–3, while stable aqueous suspensions may require pH adjustment to 7.0–9.0 to increase negative surface charge. Published data for specific injectable electrolytes is limited; saline vehicles may compress the electrical double layer and reduce network strength.
High-energy dispersion is a processing constraint. Rotor-stator homogenization or high-pressure homogenization is used to break silica agglomerates into a stable network; the energy input must be controlled because over-dispersion under excessive shear can reduce yield value and allow sedimentation. No universal mixing time can be specified across injectable vehicles because vessel geometry, batch volume, and silica concentration affect aggregate breakdown.
Because fumed silica has high surface area, it may adsorb benzalkonium chloride and other preservatives from aqueous suspensions, reducing antimicrobial effectiveness. Preservative assay should be performed after silica addition and after terminal sterilization to confirm free preservative concentration remains within the specified range.
Compendial compliance is documented by lot-specific certificates of analysis covering identification, pH, loss on drying, specific surface area, heavy metals, and microbial quality. Table 2 lists the standard references that govern release for oral and injectable excipient use.
| Attribute | Standard reference |
|---|---|
| Monograph for colloidal anhydrous silica | Ph. Eur. 0434 |
| Monograph for colloidal silicon dioxide | USP-NF Colloidal Silicon Dioxide |
| Bacterial endotoxins | Ph. Eur. 2.6.14 / USP <85> |
| Microbial enumeration and specified organisms | Ph. Eur. 2.6.12 / 2.6.13 / USP <61> / <62> |
| Elemental impurities | ICH Q3D |
| Residual solvents | ICH Q3C |
| Heavy metals, compendial limit | Ph. Eur. 2.4.8 |
For injectable dosage forms, the bacterial endotoxin requirement is additional to the oral excipient release; the absence of organic solvents in the flame hydrolysis route supports compliance with ICH Q3C, but routine solvent testing may still be required by the finished dosage form control strategy.
Aerosil R972 Pharma is a dimethylsilyl-modified fumed silica with a BET surface area in the range 90–130 m²/g and carbon content 0.7–1.3%. The surface treatment replaces a portion of the silanol groups with dimethylsilyl groups, reducing water adsorption and improving dispersibility in non-aqueous solvents, ointments, and polymer coatings. Loss on drying is lower than hydrophilic grades at ≤0.5%. The hydrophobic grade is used when the silica must function as a rheology modifier without increasing moisture sensitivity, but it is incompatible with aqueous wetting and should not be used as the sole suspending agent in water-based oral or injectable products.
In tablet coating and dry granulation, hydrophobic silica differs from hydrophilic grades in moisture response. Hydrophilic silica can absorb water from aqueous film-coating dispersions and increase viscosity unpredictably; hydrophobic Aerosil R972 Pharma can be used in non-aqueous or solvent-based barrier coatings to control thixotropy while limiting moisture uptake. In dry granulation of hygroscopic actives, the hydrophobic grade reduces capillary condensation at high RH, but it also reduces interparticulate hydrogen bonding and may lower tablet tensile strength if substituted at the same level as hydrophilic grade.
Oral suspensions benefit from the thixotropic network of Aerosil 300 Pharma at 1–3 wt%; the yield value prevents settling during storage but decreases upon shaking, allowing pourability. Viscosity recovery time depends on concentration, pH, and electrolyte content; no fixed time applies across all suspending vehicles.
Differences from other products extend to shipping and storage: fumed silica has a low tapped density, so container fill weight is low and warehousing footprint is high compared with precipitated silica and talc. The package is typically a multilayer polyethylene liner inside a fiber drum to prevent moisture uptake; open containers should be used within a defined period after initial opening. Operational boundaries include incompatibility with strong alkaline solutions, because amorphous silica dissolves via silicate formation; hydrofluoric acid also dissolves the material. Silica should not be incorporated into sterile filtration trains, and dust-forming handling should be controlled with local exhaust ventilation. The product should be stored in tightly closed containers at controlled room temperature and resealed promptly after weighing to avoid moisture sorption above 60% RH.
