Cellacefate

Cellulose, acetate, 1,2-benzenedicarboxylate.
Cellulose acetate phthalate [9004-38-0].
» Cellacefate is a reaction product of phthalic anhydride and a partial acetate ester of cellulose. It contains not less than 21.5 percent and not more than 26.0 percent of acetyl (C2H3O) groups and not less than 30.0 percent and not more than 36.0 percent of phthalyl(o-carboxybenzoyl) (C8H5O3) groups, calculated on the anhydrous, acid-free basis.
Packaging and storage— Preserve in tight containers.
Identification, Infrared Absorption 197K Do not dry specimens.
Dissolve 15 g, calculated on the anhydrous basis, in 85 g of a mixture of 249 parts of anhydrous acetone and 1 part of water, by weight: the apparent viscosity (see Procedure for Methylcellulose under Viscosity 911) is between 45 and 90 centipoises, determined at 25 ± 0.2.
not more than 5.0%, a mixture of dehydrated alcohol and methylene chloride (3:2) being used instead of methanol as the solvent.
not more than 0.1%.
0.001%.
Limit of free acid— Transfer 3.0 g, accurately weighed, to a glass-stoppered flask, add 100 mL of dilute methanol (1 in 2), insert the stopper in the flask, and shake for 2 hours. Filter, and wash the flask and the filter with two 10-mL portions of the methanol solution, adding the washings to the filtrate. Titrate the combined filtrate and washings with 0.1 N sodium hydroxide VS to a phenolphthalein endpoint. Perform a blank determination on 120 mL of the dilute methanol (1 in 2). Calculate the percentage of free acid, B, by the formula:
0.8306A/W
in which A is the volume, in mL, of 0.1 N sodium hydroxide consumed, corrected for the blank; and W is the weight, in g, of the Cellacefate, calculated on the anhydrous basis. Not more than 3.0%, calculated as phthalic acid, is found.
Phthalyl content— Transfer about 1 g, accurately weighed, to a conical flask, dissolve in 50 mL of a mixture of alcohol and acetone (3:2), add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS. Perform a blank determination, and make any necessary correction. Calculate the percentage of phthalyl, on the acid-free basis, by the formula:
100[(1.491A/W) – 1.795B]/(100 – B)
in which A is the volume, in mL, of 0.1 N sodium hydroxide consumed after correction for the blank; W is the weight, in g, of Cellacefate taken, calculated on the anhydrous basis; and B is the percentage of acid found in the test for Limit of free acid.
Content of acetyl— Transfer about 100 mg, accurately weighed, to a glass-stoppered flask, and add 25.0 mL of 0.1 N sodium hydroxide VS. Connect the flask to a reflux condenser, and reflux for 30 minutes. Cool, add 5 drops of phenolphthalein TS, and titrate with 0.1 N hydrochloric acid VS. Perform a blank determination. Calculate the free and combined acids, as acetyl, taken by the formula:
0.4305(A/W)
in which A is the volume, in mL, of 0.1 N sodium hydroxide consumed after correction for the blank; and W is the weight, in g, of Cellacefate taken, on the anhydrous basis. Calculate the percentage of acetyl, on the acid-free basis, taken by the formula:
[100(P – 0.5182B)/(100 – B)] – 0.5772C
in which P is the free and combined acids, as acetyl; B is the percentage of acid found in the test for Limit of free acid; and C is the percentage of phthalyl found in the test for Phthalyl content.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
 Topic/Question Contact Expert Committee Monograph Hong Wang, Ph.D. Scientist1-301-816-8351 (EM205) Excipient Monographs 2 Reference Standards Lili Wang, Technical Services Scientist1-301-816-8129 RSTech@usp.org
USP32–NF27 Page 1199
Pharmacopeial Forum: Volume No. 32(1) Page 179