Polyoxyl 40 Stearate

Poly(oxy-1,2-ethanediyl), -hydro--hydroxy-, octadecanoate.
Polyethylene glycol monostearate [9004-99-3].
» Polyoxyl 40 Stearate is a mixture of the mono-esters and di-esters of Stearic Acid or Purified Stearic Acid with mixed polyoxyethylene diols, the average polymer length being equivalent to about 40 oxyethylene units.
Packaging and storage— Preserve in tight containers.
Identification, Infrared Absorption 197M, on undried specimen.
Congealing temperature 651: between 37 and 47.
Acid value 401: not more than 2.
Hydroxyl value 401: between 25 and 40.
Saponification value 401: between 25 and 35.
Water, Method I 921: not more than 3.0%.
Free polyethylene glycols— Transfer about 6 g, accurately weighed, to a 500-mL separator containing 50 mL of ethyl acetate. Dissolve completely, then add 50 mL of sodium chloride solution (29 in 100), shake vigorously for 2 minutes, and allow to separate for 15 minutes. If separation is incomplete, carefully insert the separator into the well of a steam bath for short time intervals. Repeat this technique as many times as necessary to ensure the complete separation of the two phases. Cool, and drain the lower, aqueous, phase into a second 500-mL separator, and extract the upper layer with a second 50-mL portion of sodium chloride solution (29 in 100). Repeat the separation as before, including the steam bath technique to enhance complete separation. To the combined aqueous layers add 50 mL of ethyl acetate, shake vigorously for 2 minutes, and allow to separate as before. Drain the lower, aqueous phase into a third 500-mL separator, and extract it with two 50-mL portions of chloroform, by shaking for 2 minutes each time. Repeat the steam bath technique to ensure complete separation. Evaporate the combined chloroform extracts in a 150-mL beaker on a steam bath, with the aid of a stream of nitrogen, to apparent dryness. Redissolve in about 15 mL of chloroform, and transfer to a filter, collecting the filtrate in a 150-mL beaker. Rinse the funnel with several small portions of chloroform, and evaporate the combined filtrate and rinsings, as described above, until no odor of chloroform or ethyl acetate is perceptible. Dry in vacuum at 60 for 1 hour. Cool in a desiccator, and weigh: not less than 17% and not more than 27% of free polyethylene glycols is found.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Hong Wang, Ph.D.
(EM205) Excipient Monographs 2
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 1316
Pharmacopeial Forum: Volume No. 28(3) Page 720
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.