Ethylcellulose Aqueous Dispersion
» Ethylcellulose Aqueous Dispersion is a colloidal dispersion of Ethylcellulose in water. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of Ethylcellulose. It contains suitable amounts of Cetyl Alcohol and Sodium Lauryl Sulfate, which assist in the formation and stabilization of the dispersion. It may contain suitable antifoaming and antimicrobial agents.
Packaging and storage— Preserve in tight containers, and protect from freezing.
Labeling— The labeling states the ethoxy content of the Ethylcellulose and the percentage of Ethylcellulose. The labeling also indicates the names and quantities of any added antifoaming and antimicrobial agents.
USP Reference standards 11
USP Ethylcellulose RS Click to View Structure
USP Cetyl Alcohol RS Click to View Structure
A: Separately dissolve a small quantity of sample and about 250 mg of USP Ethylcellulose RS in 5 mL of a mixture of toluene and alcohol (80:20), transfer a few mL of each solution to a silver chloride plate, and evaporate the solution on each plate: the IR absorption spectrum of the residue in the 3600 to 2600 cm1 and 1500 to 800 cm1 regions exhibits maxima only at the same wave numbers as that of a film of USP Ethylcellulose RS.
B: Transfer about 2 mL to a 100-mm diameter Petri dish so that the bottom of the dish is covered uniformly. Place the dish in an oven or on a hot plate to evaporate the water: a transparent film results.
C: Dissolve the film formed in Identification test B in 20 mL of chloroform. Inject 2 µL of this solution into a gas chromatograph (see Chromatography 621) equipped with a flame-ionization detector and a 2-mm × 1.8-m column that contains 10% liquid phase G1 on support S1A. The column temperature is maintained at 220. The injection port and detector temperatures are maintained at about 250 and 275, respectively. The retention time of the major peak following the solvent peak in the resulting chromatogram corresponds to that obtained from a similar solution of USP Cetyl Alcohol RS.
D: Methylene blue solution—To a 150-mL graduated beaker containing 0.7 mL of sulfuric acid and 5 g of anhydrous sodium sulfate slowly add water to the 90-mL mark. Add methylene blue solution (3 in 1000) to the 100-mL mark, and mix.
Procedure— To 1 mL of Aqueous Dispersion in a 100-mL graduated mixing cylinder add 9 mL of water followed by 25 mL of Methylene blue solution, and mix. Add 15 mL of chloroform, and shake vigorously. Allow the two phases to separate: the lower phase is blue, indicating the presence of sodium lauryl sulfate.
Viscosity 911 Use a rotational viscosimeter equipped with a low-viscosity adapter. Mix the Aqueous Dispersion, and pipet 20 mL of it into the low-viscosity small sample adapter. Start the viscosimeter, and take readings after 60, 90, and 120 seconds at a temperature of 25 ± 2 and at a spindle speed that results in readings between 10% and 90% of full-scale. Multiply the average of the three readings by the factor specified for the spindle speed selected to obtain the viscosity in centipoises. The viscosity is not more than 150 centipoises.
pH 791: between 4.0 and 7.0.
Loss on drying— Place about 10 g of standard 20- to 30-mesh sand, previously dried for at least 30 minutes at 60, into a tared petri dish. Add 5 mL of Aqueous Dispersion, and again weigh. Dry at about 60 to constant weight: it loses not more than 71.0% of its weight.
Assay— Determine the ethoxy content, as directed under Methoxy Determination 431, using an accurately weighed portion of Ethylcellulose Aqueous Dispersion equivalent to about 25 mg of ethylcellulose. Calculate the ethylcellulose content from the ethoxy content found and the ethoxy content of the Ethylcellulose as declared in the labeling. Each mL of 0.1 N sodium thiosulfate is equivalent to 0.7510 mg of (–OC2H5).
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Topic/Question Contact Expert Committee
Monograph Robert H. Lafaver, M.S.
Scientific Liaison
(EXC2010) Monographs - Excipients
Reference Standards RS Technical Services
USP35–NF30 Page 1796
Pharmacopeial Forum: Volume No. 31(6) Page 1668