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Anionic Emulsifying Wax Excipient | Uses, Suppliers, and Specifications
Anionic Emulsifying Wax is a blend of Cetostearyl alcohol (CH3 (CH2)nOH) (n=14-16), and Sodium lauryl sulfate. As a self-emulsifying wax, it is able to build its own consistency and viscosity due to the interaction of the constituent emulsifiers, water, and fatty alcohols. Anionic emulsifying wax is supplied in the form of pellets, and exhibits a slight odour.
Synonyms and Trade Names: Emulsifying Wax Anionic; Cetostearyl Alcohol (Type A), Cetostearyl Alcohol (Type B), Emulsifying; Coltone HV; Crodex A Pharma; Lanette SX; Lanette W; Kolliphor CSA; Crodex A Pharma
Pharmacopoeial Compliance: Ph. Eur
Uses and Applications: Emulsifying Agent; Solubilising Agent, and Stiffening
Description
Anionic emulsifying wax is a waxy material obtained by blending Cetostearyl alcohol (CH3 (CH2)nOH) and Sodium lauryl sulfate. Cetostearyl alcohol is a mixture of fatty alcohols, mainly Cetyl (C16) and Stearyl (C18). Different pharmacopoeia differ in the way they specify the composition of the wax. In the Ph.Eur for instance, Anionic emulsifying wax is specified as containing NLT 80% Cetostearyl alcohol and 7% Sodium lauryl sulfate. The B.P however, describes the wax as containing 90% Cetostearyl alcohol and Sodium lauryl sulfate.
Anionic emulsifying wax is prepared by melting Cetostearyl alcohol and heating to a temperature of around 95 oC. Sodium lauryl sulfate and other ingredients are then added, and the mixture is further, with vigorous stirring to ensure the ingredients are fully incorporated. The blend is then rapidly quenched.
Note that the naming of Emulsifying wax in different pharmacopoeia is not harmonised, and is bound to cause some confusion. Below is a guide to the names used around the world for different waxes:
| USP-NF) | Ph.Eur | B.P | |
| Nonionic Emulsifying Wax | Emulsifying wax |
Not listed |
Cetomagrocol emulsifying wax |
| Anionic Emulsifying Wax | Cetostearyl alcohol Type B | Cetostearyl alcohol Type A | Cetostearyl alcohol Type A
Emulsifying Wax |
| Cationic Emulsifying Wax |
Not listed |
Not listed |
Cetrimide emulsifying wax |
Pharmaceutical-grade Anionic emulsifying wax is supplied as an almost white or pale yellow coloured, waxy solid or flaky material. It may exhibit a faint but perceptible odour.
Chemical Structure & Identifiers
| Chemical Name | Anionic emulsifying wax
(Blend of Hexadecan-1-ol and Sodium Lauryl alcohol) |
| CAS Registration Number | [8014-38-8] |
| Empirical Formula | C34H72O2 |
| Molecular weight | 512.9 g/mol |
| EINCES Number | N/A |
| UNII Code (FDA) | N/A |
Regulatory Status
Anionic emulsifying wax is officially listed in the B.P and Ph.Eur as an excipient. It is approved for use in topical pharmaceutical formulations and is generally regarded as a nontoxic and non-irritant material. It is also included in the FDA Inactive Ingredients Database (emulsions; creams, lotions, and ointments).
Physicochemical Properties
| Physical form | Solid waxy powder or flakes |
| Appearance | White or almost white or pale yellow |
| Odour | Faint, almost odourless |
| Boiling point | >150 ºC |
| Flash point | >170 ºC |
| Melting range | 49-56 °C |
| Relative density | 0.80-0.85 |
| pH value | 6-9 (10%) |
| Solubility | Insoluble in cold water. Soluble in heated oils and water (in water, a turbid solution is formed). Partially soluble in alcohol. Insoluble in Glycerol and Propylene glycol |
Pharmacopeoeal Specifications
| Specification | Ph.Eur |
| Definition | Specified |
| Characters | Specified |
| Identification | Specified |
| Acid value | ≤2.0 |
| Iodine value | ≤3.0 |
| Saponification value | ≤2.0 |
| Water | ≤3.0% |
| Assay
Cetostearyl alcohol (GC) Sodium lauryl sulfate |
Specified Specified |
| Label requirements | Specified |
Key: n/a Specification is not listed
*All claims with respect to conformity are subject to our Terms and Conditions. No express or implied warranty is made for specific properties or fitness for any particular application or purpose.
Applications in Pharmaceutical Formulations or Technology
Anionic emulsifying wax functions as an emulsifying agent in topical pharmaceutical products. The typical usage levels are 5-15%. It is recommended that the wax is added to lipid or paraffin phases of the emulsion to enable bases to facilitate smooth addition and manufacture of stable emulsions. When used in lower concentrations (e.g <2% w/w), the emulsions obtained tend to be less viscous, whereas levels in excess of 10% yield thick, non-pourable products.
Note that due to the presence of water in the wax, the product made with Anionic emulsifying wax should incorporate a suitable preservative. If required, they may be sterilized, for instance, by autoclaving. The addition of an alkali (e.g Triethanolamine, TEA) has been shown to improve emulsion quality.
At levels of between 3 and 30%, Anionic emulsifying wax can be blended with Petrolatum and Parrafin wax to produce an anhydrous ointment base, which finds utility as a soap replacement in the management of eczematous conditions. It may also be used to fabricate suppository bases (m.p approx. 34 °C) when blended with Cocoa butter.
Safety and Precautions
Long-chain aliphatic alcohols such as Cetostearyl alcohol are commonly added to skin products where they serve as emollients, thickeners, humectants, and foam stabilizers. Several studies have examined the toxicity of such fatty alcohols and shown that they induced minimal ocular and skin irritation and no sensitisation or comedogenicity in animals; and certainly, no mutagenic effects were noted in the Ames assay. Based on these studies, it was concluded that long-chain fatty alcohols are safe as ingredients in topical products. A link to one such study can be found by click here.
Stability and Storage Conditions
Anionic emulsifying wax is a stable material provided it is correctly handled and stored. Containers should well-closed and placed in a cool, dry place away from moisture and heat.
Anionic emulsifying wax is incompatible with sodium alkyl sulfates, cationic compounds such as quaternary ammonium compounds, salts of polyvalent metals (aluminum, zinc, tin, and lead), and thioglycolates. Anionic emulsifying wax is compatible with most acids above pH 2.5. It is also compatible with alkalis and hard water.
When handling Anionic emulsifying wax in an industrial setting, observance of SHE precautions appropriate to the circumstances and quantity of material being handled is expected. Eye protection is recommended.
Sustainability and Environmental Impact
A sustainability score for Anionic Emulsifying Was has not yet been determined.
Manufacturers & Suppliers
Additional Resources (Downloads)
References and Literature Used
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