Edition: BP 2025 (Ph. Eur. 11.6 update)
(Ph. Eur. monograph 1123)
Action and use
Non-ionic surfactant.
DEFINITION
Mixture of ethers of mixed macrogols with linear fatty alcohols, mainly cetostearyl alcohol. It may contain some free macrogols and it contains various amounts of free cetostearyl alcohol. The number of moles of ethylene oxide reacted per mole of cetostearyl alcohol is 2 to 33 (nominal value).
CHARACTERS
Appearance
White or yellowish-white, waxy, unctuous mass, pellets, microbeads or flakes.
Solubility
Macrogol cetostearyl ether with low numbers of moles of ethylene oxide reacted per mole: practically insoluble in water, soluble in ethanol (96 per cent) and in methylene chloride;
Macrogol cetostearyl ether with higher numbers of moles of ethylene oxide reacted per mole: dispersible or soluble in water, soluble in ethanol (96 per cent) and in methylene chloride.
It solidifies at 32 °C to 52 °C.
IDENTIFICATION
A. Hydroxyl value (see Tests).
B. Iodine value (see Tests).
C. Saponification value (see Tests).
D. Thin-layer chromatography (2.2.27).
Test solution: Dissolve the prescribed amount of substance to be examined (see table below) in a mixture of 1 volume of water R and 9 volumes of methanol R and dilute to 75 mL with the same mixture of solvents.
| Number of moles of ethylene oxide reacted per mole | Amount to be dissolved (g) |
|---|---|
| 2 – 6 | 5.0 |
| 10 – 22 | 10.0 |
| 25 – 33 | 15.0 |
Add 60 mL of hexane R and shake for 3 min. The formation of foam can be reduced by the addition of some drops of ethanol (96 per cent) R. Filter the upper layer through anhydrous sodium sulfate R, wash the filter with 3 quantities, each of 10 mL, of hexane R and evaporate the combined filtrates to dryness. Dissolve 0.05 g of the residue in 10 mL of methanol R (the solution may be opalescent).
Reference solution: Dissolve 25 mg of stearyl alcohol CRS in methanol R and dilute to 25 mL with the same solvent.
Plate: TLC silica gel plate R.
Mobile phase: ethyl acetate R.
Application: 20 µL.
Development: Over a path of 15 cm.
Drying: In air.
Detection: Spray with vanillin-sulfuric acid reagent prepared as follows: dissolve 0.5 g of vanillin R in 50 mL of ethanol (96 per cent) R and dilute to 100 mL with sulfuric acid R; allow to dry in air; heat at about 130 °C for 15 min and allow to cool in air.
Results: The chromatogram obtained with the test solution shows several spots; one of these spots corresponds to the principal spot in the chromatogram obtained with the reference solution.
E. Dissolve or disperse 0.1 g in 5 mL of ethanol (96 per cent) R, add 2 mL of water R, 10 mL of dilute hydrochloric acid R, 10 mL of barium chloride solution R1 and 10 mL of a 100 g/L solution of phosphomolybdic acid R. A precipitate is formed.
TESTS
Appearance of solution
The solution is not more intensely coloured than reference solution BY5 (2.2.2, Method II).
Dissolve 5.0 g in ethanol (96 per cent) R and dilute to 50 mL with the same solvent.
Alkalinity
Dissolve 2.0 g in a hot mixture of 10 mL of ethanol (96 per cent) R and 10 mL of water R. Add 0.1 mL of bromothymol blue solution R1. Not more than 0.5 mL of 0.1 M hydrochloric acid is required to change the colour of the indicator to yellow.
Acid value (2.5.1)
Maximum 1.0, determined on 5.0 g.
Hydroxyl value (2.5.3, Method A)
| Number of moles of ethylene oxide reacted per mole (nominal value) | Hydroxyl value |
|---|---|
| 2 | 150 – 180 |
| 3 | 135 – 155 |
| 5–6 | 100 – 134 |
| 10 | 75 – 90 |
| 12 | 67 – 77 |
| 15 | 58 – 67 |
| 20–22 | 40 – 55 |
| 25 | 36 – 46 |
| 30–33 | 32 – 40 |
Iodine value (2.5.4, Method A)
Maximum 2.0.
Saponification value (2.5.6)
Maximum 3.0, determined on 10.0 g.
Ethylene oxide and dioxan (2.4.25)
Maximum 1 ppm of ethylene oxide and maximum 10 ppm of dioxan.
Water (2.5.12)
Maximum 3.0 per cent, determined on 2.00 g.
Total ash (2.4.16)
Maximum 0.2 per cent, determined on 2.0 g.
STORAGE
In an airtight container.
LABELLING
The label states the number of moles of ethylene oxide reacted per mole of cetostearyl alcohol (nominal value).
