Cetostearyl Alcohol

(Ph. Eur. monograph 0702)

Excipient.

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Mixture of solid aliphatic alcohols, mainly octadecan-1-ol (stearyl alcohol; C₁₈H₃₈O; M_r 270.5) and hexadecan-1-ol (cetyl alcohol; C₁₆H₃₄O; M_r 242.4), of animal or vegetable origin.

• — stearyl alcohol: minimum 40.0 per cent,

• — sum of the contents of stearyl alcohol and cetyl alcohol: minimum 90.0 per cent.

White or pale yellow, wax-like mass, plates, flakes or granules.

Practically insoluble in water, soluble in ethanol (96 per cent) and in light petroleum. When melted, it is miscible with fatty oils, with liquid paraffin and with melted wool fat.

Examine the chromatograms obtained in the assay.

Results  The 2 principal peaks in the chromatogram obtained with the test solution are similar in retention time to the principal peaks in the chromatogram obtained with the reference solution.

The solution is clear (2.2.1) and not more intensely coloured than reference solution B₆ (2.2.2, Method II).

Dissolve 0.50 g in 20 mL of boiling ethanol (96 per cent) R. Allow to cool.

49 °C to 56 °C.

Maximum 1.0.

208 to 228.

Maximum 2.0.

Dissolve 2.00 g in methylene chloride R and dilute to 25 mL with the same solvent.

Maximum 2.0.

Gas chromatography (2.2.28): use the normalisation procedure.

Test solution  Dissolve 0.100 g of the substance to be examined in ethanol (96 per cent) R and dilute to 10.0 mL with the same solvent.

Reference solution  Dissolve 60 mg of cetyl alcohol CRS and 40 mg of stearyl alcohol CRS in ethanol (96 per cent) R and dilute to 10 mL with the same solvent. Dilute 1 mL of this solution to 10 mL with ethanol (96 per cent) R.

• — size: l = 30 m, Ø = 0.32 mm,

• — stationary phase: poly(dimethyl)siloxane R (1 µm).

Carrier gas  helium for chromatography R.

Flow rate  1 mL/min.

Split ratio  1:100.

Temperature:

Detection  Flame ionisation.

Injection  1 µL.

System suitability  Reference solution:

• — resolution: minimum 5.0 between the peaks due to cetyl alcohol and stearyl alcohol.

Calculate the percentage contents of C₁₆H₃₄O and C₁₈H₃₈O.

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