Friday, 17 July 2009

Monographs: Pharmaceutical substances: Cetomacrogolum 1000 - Cetomacrogol 1000


Chemical name. Polyethylene glycol monohexadecyl ether; α-hexadecyl-ω-hydroxypoly(oxy-1,2-ethanediyl); CAS Reg. No. 9004-95-9.

Description. A cream-coloured, waxy, unctuous mass, pellets, or flakes; when heated, it melts to a brownish yellow, clear liquid; odourless or almost odourless.

Solubility. Soluble in water, ethanol (~750 g/l) TS, and acetone R; practically insoluble in light petroleum R.

Category. Nonionic surfactant.

Storage. Cetomacrogol 1000 should be kept in a well-closed container, protected from heat.


Definition. Cetomacrogol 1000 is a condensation product of linear fatty alcohols with ethylene oxide, prepared under controlled conditions in order to obtain the required ether with the polyethylene glycol of the desired molecular mass.

Identity tests

A. Dissolve 0.1 g in 5 ml of water and add 10 ml of hydrochloric acid (~70 g/l) TS, 10 ml of barium chloride (50 g/l) TS, and 10 ml of phosphomolybdic acid (80 g/l) TS; a greenish yellow precipitate is produced.

B. Dissolve 0.1 g in 5 ml of water and add gradually tannic acid (50 g/l) TS; a precipitate is formed which dissolves on further addition of tannic acid solution.

Melting point. Not lower than 38 °C.

Refractive index. At 60 °C,

Acid value. Not more than 0.5.

Alkalinity. Dissolve 2 g in 20 ml of carbon-dioxide-free water R, add 1 drop of phenolphthalein/ethanol TS, and titrate with hydrochloric acid (0.1 mol/l) VS; not more than 0.5 ml is required to obtain a pink colour.

Hydroxyl value. Use 10 g, Method A; 40.0-52.5.

Saponification value. Use 10 g; not more than 1.0.

Water. Determine as described under 2.8 Determination of water by the Karl Fischer method, Method A, using 2.5 g; the water content is not more than 10 mg/g.

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