Beta-cyclodextrin (β-CD, CAS 7585-39-9) is a cyclic oligosaccharide of seven glucose units with a hydrophilic exterior and a hydrophobic internal cavity – the reason it can trap a guest molecule inside a water-soluble shell. PolyBlueChem supplies β-cyclodextrin as a white crystalline powder, assay 98.0-102.0%, with per-batch COA and SDS.
Specifications
| Property | Specification |
|---|---|
| Appearance | White crystal powder, odourless, slightly sweet |
| Solubility | Slightly soluble in water; almost insoluble in methanol, ethanol, acetone or diethyl ether |
| Clarity of solution | Clear and colourless |
| pH | 5.0 – 8.0 |
| Specific rotation | +159° to +164° |
| Chloride | 0.018% max |
| Light-absorbing impurities | 0.10 max (230-350 nm); 0.05 max (350-750 nm) |
| Reducing sugars | 1.0% max |
| Cyclohexane | 0.388% max |
| Loss on drying | 14.0% max |
| Residue on ignition | 0.1% max |
| Heavy metals | 10 ppm max |
| Assay | 98.0% – 102.0% |
| Total aerobic microbial count | 1000 cfu/g max |
| Total combined moulds and yeasts | 100 cfu/g max |
| Escherichia coli | Absent |
Three specification items deserve comment because they are the ones that get missed in a price comparison:
- Loss on drying up to 14% is normal, not a defect. β-cyclodextrin crystallises as a hydrate and carries roughly ten molecules of water; the assay is quoted on the dried basis for that reason. Comparing a 14%-water lot with a 10%-water lot on price per kilogram compares different amounts of cyclodextrin.
- Cyclohexane is listed as a residual solvent. Not every β-cyclodextrin process involves it, so its presence on this specification tells you something about the route. Confirm the level against the ICH Q3C limit for your market rather than assuming a “natural” excipient is solvent-free.
- Specific rotation is the identity test. Assay tells you how much cyclodextrin is present; optical rotation tells you which cyclodextrin. The three homologues sit in different ranges, so a rotation outside +159 to +164 should prompt a question about alpha- or gamma-cyclodextrin content.
Basic Information
| CAS number | 7585-39-9 |
| Chemical name | β-Cyclodextrin; cycloheptaamylose; β-cycloheptapentylose |
| Formula / MW | C42H70O35 / 1135.0 g/mol (anhydrous) |
| PubChem CID | 444041 |
| Type | Cyclic oligosaccharide (seven glucose units) |
| Food additive number | E459 (cyclodextrin, as a carrier and stabiliser, where permitted) |
What the cavity does
The molecule is a truncated cone: the outside is covered in hydroxyl groups and is therefore water-loving, while the inside of the cone is lined with the hydrophobic faces of the glucose rings. A guest molecule of the right size and polarity can enter the cavity and be held there by van der Waals forces and hydrogen bonding – a non-covalent inclusion complex, not a chemical reaction.
| Homologue | Glucose units | Cavity diameter (approx.) | Typical guest |
|---|---|---|---|
| α-Cyclodextrin (CAS 10016-20-3) | 6 | 4.7-5.3 Å | Small molecules, short-chain fatty acids, flavour volatiles |
| β-Cyclodextrin (this product) | 7 | 6.0-6.5 Å | Most drug-like molecules, vitamins, essential-oil components |
| γ-Cyclodextrin (CAS 17465-86-0) | 8 | 7.5-8.3 Å | Larger guests, steroids, some peptides |
The cavity size is the design parameter. A guest that is too small rattles inside and releases easily; one that is too large never enters. β-cyclodextrin’s 6-6.5 Å cavity happens to match a very large number of pharmaceutical and flavour molecules, which is why it is the most widely used of the three – despite being the least water-soluble.
Applications
- Pharmaceutical excipient – solubility and stability enhancement, taste masking, and conversion of liquids or oils into free-flowing powders by complexation.
- Food ingredient – carrier and stabiliser for flavours, colours and vitamins (E459); protection of sensitive actives from oxidation and light.
- Cosmetics and personal care – controlled release of fragrance, stabilisation of oxidation-sensitive actives, odour masking.
- Agrochemical formulations – improved wetting and bioavailability of poorly soluble actives.
- Environmental and separation uses – sorption of organic pollutants, chiral separation and analytical sample preparation.
Buying notes
- State the assay basis. 98.0-102.0% is quoted on the dried basis; combine it with loss on drying to get the as-received content.
- Ask for the specific rotation on the COA, not only the assay – it is the cheapest check that you received β- and not another homologue.
- Ask for the residual solvent set and confirm the cyclohexane figure against your market’s limit.
- Check microbial limits if the material goes into a food or sterile-adjacent application; the specification above is a food-grade package, not a sterile one.
- For high-concentration formulations, ask about the derivatives – hydroxypropyl and sulfobutyl ether β-cyclodextrins dissolve far more freely than the parent compound.
Packaging and supply
Supplied as a white crystalline powder in 25 kg fibre drums or bags with an inner liner, and in smaller sealed packs for development work. Store sealed, cool and dry; the material is a hydrate and will pick up or lose moisture with the ambient humidity, so the loss-on-drying figure should be checked on receipt rather than assumed from the certificate. Each lot ships with a COA and SDS, and FOB or CIF terms are quoted against destination. Where the material is destined for food or pharmaceutical use, say so at enquiry stage so the documentation package matches the destination market.
Further reading
- Beta-cyclodextrin: properties, inclusion chemistry and applications
- Alpha, beta or gamma cyclodextrin – and when a derivative is the right answer
- Cyclodextrin in food and pharmaceutical use: E459, pharmacopoeial status and what to verify
PolyBlueChem supplies β-cyclodextrin (CAS 7585-39-9), assay 98.0-102.0% on the dried basis, white crystalline powder, with per-batch COA and SDS and FOB/CIF delivery. Send your specification, quantity and destination, and we will confirm the lot and the documentation package.
