| HS Code | 834379 |
| Chemical Name | Sodium selenite |
| Chemical Formula | Na2SeO3 |
| Cas Number | 10102-18-8 (anhydrous); 26970-82-1 (pentahydrate) |
| Molecular Weight | 172.94 g/mol (anhydrous) |
| Appearance | White crystalline powder |
| Odor | Odorless |
| Solubility | Soluble in water; slightly soluble in alcohol |
| Melting Point | Decomposes at approximately 350°C (anhydrous) |
| Ph | 9.0 to 10.0 (0.1% aqueous solution) |
| Assay | 98.0% to 101.0% on dried basis (FCC) |
| Selenium Content | Approximately 45.7% |
| Storage Conditions | Keep container tightly closed in a cool, dry place |
As an accredited Food Grade Sodium Selenite (FCC) factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Food Grade Sodium Selenite (FCC) packaged in 25 kg sealed fiber drums with double polyethylene liners for safe handling. |
| Container Loading (20′ FCL) | 20′ FCL securely loaded with Food Grade Sodium Selenite (FCC) in sealed drums, palletized, protected from moisture and contamination during transit. |
| Shipping | Food Grade Sodium Selenite (FCC) ships as a regulated hazardous material due to selenium toxicity. It must be packed in sealed, moisture-resistant containers, labeled appropriately, and transported with proper documentation. Avoid contact with acids, strong oxidizers, or foodstuffs. Follow international, federal, and local dangerous goods regulations during ground, air, or ocean freight. |
| Storage | Store Food Grade Sodium Selenite (FCC) in a tightly sealed, original container in a cool, dry, well-ventilated area. Protect from moisture, direct sunlight, and extreme temperatures. Keep away from acids, strong oxidizers, and foodstuffs. Ensure proper labeling and secure access to prevent accidental ingestion or contamination. |
| Shelf Life | Shelf life is typically 2 years when stored in a cool, dry, tightly sealed container away from light and moisture. |
In dry oral dosage operations, the limiting constraint is not the incoming assay but the ability to maintain content uniformity when selenium is dosed at 55 µg per tablet—equivalent to 120.4 µg of anhydrous sodium selenite per unit. The material is accepted against the FCC Sodium Selenite monograph with an assay acceptance range of 98.0–100.5% on the dried basis and a selenium content of 45.6 wt% on an anhydrous basis, and the finished supplement is produced under 21 CFR 111 current good manufacturing practice and, in the European Union, the permitted source listing in Annex II of Directive 2002/46/EC. A production-scale dry blend begins with a single-stage preblend of sodium selenite into microcrystalline cellulose or dicalcium phosphate at a 1:100 ratio inside a 3000 L twin-shell V-blender fitted with an intensifier bar; the preblend is discharged through a 500 µm screen and then added to a 2000 kg main blend of ascorbate-free multilayer minerals in a horizontal ribbon blender running at 25 rpm for 12–15 min. Content uniformity is verified under USP <905> on 10 composite samples taken at the beginning, middle, and end of the compression run; acceptance is based on an acceptance value ≤ 15. The compression operation on a 45-station rotary tablet press at 60–70 rpm is the preferred terminal step, and hard-shell capsules are filled either with the same preblend or with a trituration containing 0.5% active sodium selenite to avoid segregation. The compression platform produces single-entity selenium tablets at 55 µg, 100 µg, and 200 µg selenium, multivitamin-mineral tablets, and two-piece hard capsules; for a 100 µg selenium unit, the sodium selenite mass rises to 219 µg, and for 200 µg selenium it rises to 438 µg. Effervescent and high-ascorbic-acid low-pH formulations are excluded unless a polymer barrier or separate granulation is used, because free sodium selenite in the presence of ascorbic acid and moisture can reduce to elemental selenium and produce visible red specks. In dry systems, relative humidity is held below 40% in the compression suite, and any wet granulation step is performed with purified water at a pH above 5.0 to avoid formation of elemental selenium.
Because infant formula is a continuous wet-mix operation, the point of addition determines whether sodium selenite remains in the aqueous phase, adsorbs to casein micelles, or is lost during downstream reconstitution. The controlling specification is the finished product selenium content, not the amount of salt added at the mixing vessel: under Regulation (EU) 2016/127 Annex I, selenium in infant formula is set at 3–8.5 µg/100 kcal, while 21 CFR 107.100 establishes a US range of 2–7 µg/100 kcal. For a standard spray-dried powder with an energy density of 500 kcal/100 g, the corresponding sodium selenite addition ranges from 0.329 mg/kg to 0.931 mg/kg under the EU profile and from 0.219 mg/kg to 0.767 mg/kg under the US profile; these values are calculated using the 45.6 wt% selenium content of anhydrous sodium selenite. In manufacturing, the mineral premix is prepared separately in a stainless steel vessel at 40–50 °C and added after the protein-fat-carbohydrate base has been hydrated, deaerated, and cooled to below 60 °C. Early addition to a reducing sugar phase of a thermally processed mix can accelerate the redox conversion of selenite to elemental selenium. The mixture is homogenized in a two-stage high-pressure homogenizer at 250/50 bar, pasteurized as part of the standard process, and spray-dried through a nozzle tower at an inlet temperature of 180–190 °C and an outlet temperature of 85–90 °C. Finished formats span spray-dried infant formula powder, follow-on formula powder, hydrolyzed protein formula, and ready-to-feed liquid formula that has been retorted or UHT-treated; in liquid formats, the finished selenium content is confirmed by microwave-assisted ICP-MS after digestion, and batch release includes stability data for selenium retention through the declared shelf life. Sodium selenite is not interchangeable with selenium yeast on a weight basis in these formulations, and reformulation requires recalculation against the labeled energy value because the selenium allowance is tied to 100 kcal, not to total mass.
| Regulatory basis | Selenium target | Selenium content in powder | Na2SeO3 addition |
|---|---|---|---|
| Regulation (EU) 2016/127 Annex I | 3–8.5 µg/100 kcal | 150–425 µg/kg | 0.329–0.931 mg/kg |
| 21 CFR 107.100 | 2–7 µg/100 kcal | 100–350 µg/kg | 0.219–0.767 mg/kg |
Selenium recovery in indirect tubular UHT systems depends less on thermal destruction than on partitioning to adsorbed protein-mineral fouling layers on heat exchanger surfaces. In a high-protein formula with a caloric density of 1.5 kcal/mL, a prescribed selenium concentration of 20 µg/100 mL requires 43.8 µg of anhydrous sodium selenite per 100 mL, or 0.438 mg per liter, based on the 45.6 wt% selenium equivalence; the actual addition is adjusted after the first full-scale lot by measuring selenium retention in the final aseptic fill. The applicable source and composition framework is Regulation (EU) 2016/128 for foods for special medical purposes and, for analytical control, a laboratory operating under EN 17025:2017 with closed-vessel microwave digestion and ICP-MS quantification. In production, sodium selenite is combined with the other heat-stable trace minerals in a nitrogen-blanketed dosing vessel and injected into the aqueous phase after the protein has been hydrated and the pH stabilized between 6.8–7.1; the blend is then homogenized, preheated, and processed through an indirect tubular UHT system at 141–145 °C for 4–6 s, followed by aseptic cooling to 20–25 °C. Headspace oxygen is maintained below 2% in the filling zone, because oxidative conditions combined with residual ascorbate in a clinical formula can progressively reduce selenite to insoluble selenium. The output of this line includes ready-to-hang tube feeds at 1.0 kcal/mL, oral sip feeds at 1.5–2.4 kcal/mL, and powdered FSMP intended for reconstitution; for powders, the selenium addition is placed in the dry mineral premix after spray drying rather than in the base wet mix when the base contains high levels of reducing sugars. Published data for the exact retention coefficient in this specific UHT configuration is limited; therefore, the overage is not fixed in this specification and must be established for each line at qualification.
Maintaining blend uniformity at a sodium selenite concentration of 4.0 mg/kg in a 30 g serving is the controlling problem for dry powder stick-pack operations running at 220 fills/min on a vertical form-fill-seal machine. The sodium selenite fraction is not added as a straight powder but as a milled 1% active premix dispersed on maltodextrin DE 10–12 or dicalcium phosphate dihydrate. A serving target of 55 µg selenium corresponds to 120.4 µg of anhydrous sodium selenite per serving, equivalent to 4.0 mg/kg in the finished powder and 4.0 g of active compound per 1000 kg of finished powder when the serving mass is 30 g; at this order of magnitude, direct addition without geometric dilution would produce a coefficient of variation that routinely exceeds 10% after 30 s of main blending. The premix is first prepared in a 200 L drum blender at 1:100 dilution with the carrier, passed through a 600 µm conical mill to remove agglomerates, and then introduced into a 1500 kg ribbon mixer with the main powder blend. The final mix is filled into polypropylene/foil/polyethylene stick packs with a water vapor transmission rate below 0.05 g/m²/24 h; the foil layer provides an effective light transmission of 0% because selenium salts are hygroscopic and redispersion of a moisture-damaged premix can lead to localized redox hotspots. The formulation is governed by the labeling provisions of Regulation (EU) 1169/2011 and the selenium NRV of 55 µg; in the United States, the reference daily intake is aligned at 55 µg under 21 CFR 101.9. Finished formats include high-protein meal replacement shake powders, whey and plant protein blends, sports recovery powders, and collagen-containing drink mixes, provided that the formula does not use wet granulation with ascorbic acid at low pH. Water activity of the finished powder is held below 0.30, and residual moisture below 4% in the sealed stick pack, as measured by a Karl Fischer method.
A total diet replacement bar with a finished water activity of 0.38–0.42 and a total protein content above 30% requires sodium selenite to be incorporated through the binder syrup rather than the dry protein phase. The regulatory input is Regulation (EU) 2017/1798, under which total diet replacement for weight control must supply the reference amount of selenium across the daily ration; when the full daily ration is defined as 55 µg selenium, the corresponding anhydrous sodium selenite input is 120.4 µg per day as a raw material. In a 55 g meal bar, the mineral premix is dispersed in a maltitol or glycerol binder syrup at 45–50 °C before the syrup is added to a continuous paddle mixer at 35–40 rpm; the syrup addition rate is set so that the bar mass after forming and cooling falls within ±2% of target, because the selenium dose is mass-proportional and cannot be adjusted downstream. The mixed mass is then transferred through a cold-forming bar line or a slab-and-slit system with cutting at 10–12 °C, followed by enrobing or packaging in high-barrier film; the cold-forming step limits deformation of the protein matrix and prevents the mineral premix from migrating to the bar surface. The bar line outputs total diet replacement bars, high-protein weight-management bars, and portioned coated bars for at-home meal replacement programs; uncoated bars are excluded from the sodium selenite version where the surface water activity rises above 0.50 during storage, because surface moisture can mobilize the salt and produce visible point specking. No reducing ascorbic acid phase is used in this matrix; if vitamin C is required, it is added as a separate coated granule or as a later-stage dry particle with a hydrophobic coating to avoid direct contact with the sodium selenite fraction.
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Food Grade Sodium Selenite (FCC) is an anhydrous inorganic selenium salt with the chemical formula Na2SeO3, CAS registry number 10102-18-8, and formula weight 172.94 g/mol. The theoretical selenium content, calculated from IUPAC standard atomic weights, is 45.66% by mass; the Food Chemicals Codex monograph acceptance range for selenium is 44.0% to 46.0%, and assay is controlled at 98.0% to 101.0% Na2SeO3 on the anhydrous basis. The material is a white to faintly pink crystalline powder, freely soluble in water, and is used as a controlled selenium source in dietary supplement tablets, food fortification premixes, and special-nutrition formulations. Unlike technical-grade sodium selenite supplied for glass decolourising or metallurgical baths, the FCC grade carries a documented food chemical codex compliance matrix and a lower elemental-impurity profile.
No universal model code governs this product; the grade is identified by the compendial monograph, anhydrous assay, and certificate of analysis. Purchase specifications should state “food grade sodium selenite, FCC” and require the supplier to report lot-specific values for assay, selenium content, loss on drying, and elemental impurities. Industrial-grade sodium selenite, including material produced for glass decolourising and metallurgical electrolyte baths, is not interchangeable with this product because its impurity profile is not controlled under the FCC monograph and may contain residual selenite process streams with elevated lead, cadmium, or mercury.
The compendial compliance matrix for a typical lot-release program is shown below. Because the FCC is revised periodically, the values shown should be checked against the exact monograph edition referenced in the receiving specification.
| Parameter | Acceptance range | Analytical basis |
|---|---|---|
| Assay as Na2SeO3, anhydrous basis | 98.0%–101.0% | FCC Sodium Selenite Monograph |
| Selenium content | 44.0%–46.0% | FCC Sodium Selenite Monograph |
| Loss on drying | ≤1.0% | FCC loss-on-drying method |
| Lead | ≤2 mg/kg | FCC elemental impurities method |
| Cadmium | ≤1 mg/kg | FCC elemental impurities method |
| Arsenic | ≤3 mg/kg | FCC elemental impurities method |
| Mercury | ≤1 mg/kg | FCC elemental impurities method |
Verification of selenium content in the finished product is usually performed by inductively coupled plasma mass spectrometry after microwave-assisted acid digestion. The FCC monograph oxidation-reduction titration or atomic absorption method may be used for release, but ICP-MS provides lower detection limits and distinguishes selenium mass from matrix interferences. This is relevant in premixes containing iodate, copper, or iron, where redox interferences can distort an iodometric titration. Method precision should be validated at the expected use level; for a premix at 250 mg Se/kg, routine duplicate agreement within 3% relative percent difference is generally expected.
Direct addition of neat sodium selenite at finished-product scale is limited by the mass fraction of selenium in the salt. A finished product target of 55 µg selenium per serving would require only about 0.12 mg of anhydrous sodium selenite per serving, a level poorly suited to direct weighing on production-scale batch weighers. At a batch size of 100,000 servings, the neat salt requirement is approximately 12 g, which can be weighed accurately, but distribution uniformity rather than weighment is the limiting factor. The preferred manufacturing route is preparation of a dilute premix by geometric dilution with a carrier such as dicalcium phosphate, maltodextrin, or microcrystalline cellulose. In a 500 kg ribbon blender, a 1% sodium selenite premix can be produced by pre-sieving the active salt through a 250 µm screen and blending for 15 min to 20 min at 40% to 70% gross fill volume.
Segregation is the dominant processing risk. Anhydrous sodium selenite has a fine particle size distribution and may become electrostatically charged in low-humidity dry blending suites; when it is combined with coarse carriers, the active salt can migrate to the bottom of tumble mixers or adhere to stainless steel surfaces. This behavior is addressed by matching the carrier particle size as closely as possible and by controlling relative humidity within the mixing room. If the salt has been exposed to relative humidity above 60%, pre-drying is required before blending because surface moisture increases agglomeration and reduces flow through rotary tablet press tooling.
For two-piece hard capsules, the selenium source is often filled as a preblend with lactose or dicalcium phosphate. Published data for this specific configuration is limited; however, the salt’s particle size and flow behavior should be tested before high-speed encapsulation. In production-scale rotary tablet presses, a premix with poor flow can cause die feed variability; weight variation has been observed to exceed 2.0% when the component ratio is not optimized. The addition of 0.5% to 1.0% colloidal silicon dioxide and avoidance of prolonged storage before compression are typical corrective actions.
The FCC grade is defined by identity, purity, and elemental impurity controls intended for food and supplement use. It is not automatically equivalent to USP or EP grades because each compendium has different test panels; USP may apply additional tests for bacterial endotoxins and residual solvents, while the FCC monograph is oriented toward food additive use. In food fortification programs, the final product must comply with local food law, which may specify permitted selenium sources and final selenium limits. The FCC monograph itself is not a use authorisation; it provides the identity and purity standard for the ingredient.
Documented certification under food safety management systems such as ISO 22000 and current Good Manufacturing Practice for dietary supplements is expected from suppliers. A complete lot package should include the FCC certificate of analysis, a heavy metal analysis by ICP-MS, allergen statements, and identity verification by oxidation-reduction titration or atomic absorption spectrometry. Material lacking lot-specific documentation should not be accepted as food grade, regardless of visual similarity.
Sodium selenite is not freely interchangeable with sodium selenate or organic selenium sources. Sodium selenate carries selenium in the +6 oxidation state and has a different anion chemistry; selenite carries selenium in the +4 oxidation state. Sodium selenate has a higher formula weight and lower theoretical selenium content; anhydrous sodium selenate has a selenium content of approximately 41.8% versus 45.66% for sodium selenite. Substitution therefore requires rebalancing the selenium claim and revalidation of the final product assay.
Selenomethionine and selenium-enriched yeast are organic selenium forms. Selenomethionine is incorporated into body proteins in place of methionine, whereas selenite is reduced through selenide intermediates and enters selenoprotein synthesis through a different metabolic route. These metabolic differences affect retention and tissue distribution, and they mean that a one-to-one mass replacement between sodium selenite and selenium yeast is not supported by the same labelling or bioavailability statement.
In aqueous systems, sodium selenite is chemically incompatible with reducing agents under acidic conditions. Ascorbic acid, sulfur dioxide, and reducing sugars can reduce selenite to elemental selenium, producing a red colloidal precipitate and effectively removing the nutrient from the soluble fraction. This reaction is pH-dependent and is more rapid below pH 4.0. Ready-to-drink formulations that contain ascorbic acid require either microencapsulation, separate compounding, or selection of a different selenium source. The salt should also be kept away from strong acids because acidification of concentrated selenite solutions can liberate volatile selenium species and create industrial hygiene risks.
In storage, the product should be kept in tightly closed, food-grade packaging with a low water vapour transmission rate. Physical segregation of the finished ingredient from reducing agents and food acids is required. Typical pack sizes include 25 kg fibre drums with polyethylene liners; however, pack size is supplier-specific and should be specified in the purchasing agreement. Production-scale handling should be conducted under negative containment with local exhaust ventilation because the fine particle size can increase operator exposure during screening and transfer.