Ethylcellulose, chemical structure, molecular formula, Reference Standards

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Ethylcellulose

Cellulose,ethyl ether.
Cellulose ethyl ether [9004-57-3].

»Ethylcellulose is a partlyO-ethylated cellulose.It contains not less than 44.0percent and not more than 51.0percent of ethoxy (–OC2H5)groups,calculated with reference to the dried substance.

Packaging and storage— Preserve in well-closed containers.

Labeling— Label it to indicate its nominal viscosity in millipascal seconds for a 5percent m/m solution.

USP Reference standards á11ñ— USP Ethylcellulose RS.

Identification,Infrared Absorption á197Kñ.

Viscosity á911ñ— Shake a quantity of ethylcellulose equivalent to 5.00g of the dried substance with 95g of a mixture of 20g of alcohol and 80g of toluene until the substance is dissolved.Determine the viscosity using a capillary viscosimeter.The viscosity,determined at 25

and expressed in mPa·s,is not less than 80.0%and not more than 120.0%of that stated on the label for a nominal viscosity greater than 6mPa·s;and not less than 75.0%and not more than 140.0%of that stated on the label for a nominal viscosity not greater than 6mPa·s.

Acidity or alkalinity— To 0.5g of ethylcellulose,accurately weighed,add 25mLof carbon dioxide-free water and shake for 15minutes.Pass through a sintered-glass filter with a maximum diameter of pores between 16µm and 40µm.To 10mLof this solution,add 0.1mLofPhenolphthalein solution and 0.5mLof 0.01Nsodium hydroxide.The solution is pink.To 10mLof this solution,add 0.1mLofMethyl red solution and 0.5mLof 0.01Nhydrochloric acid.The solution is red.

Phenolphthalein solution— Dissolve 100mg of phenolphthalein in 80mLof alcohol,and dilute with water to 100mL.

Methyl red solution— Dissolve 50mg of methyl red in a mixture of 1.86mLof 0.1Nsodium hydroxide and 50mLof alcohol,and dilute with water to 100mL.

Loss on drying á731ñ— Dry it at 105

for 2hours:it loses not more than 3.0%of its weight.

Residue on ignition á281ñ: not more than 0.5%,determined on 1.0g.

Heavy metals,Method IIá231ñ: 20µg per g.

Acetaldehyde— Introduce 3.0g into a 250-mLconical flask with a ground-glass stopper,add 10mLof water,and stir by mechanical means for 1hour.Allow to stand for 24hours,filter,and dilute the filtrate with water to 100.0mL.Transfer 5.0mLto a 25mLvolumetric flask,add 5mLof a 0.5g per Lsolution of methylbenzothiazolone hydrazone hydrochloride,and heat in a water bath at 60

for 5minutes.Add 2mLofFerric chloride–sulfamic acid reagent,and heat again at 60

for 5minutes.Cool,and dilute with water to 25.0mL.The solution is not more intensely colored than a standard prepared at the same time and in the same manner using,instead of the 5.0mLof the filtrate,5.0mLof a reference solution prepared by diluting 3.0mLofAcetaldehyde standard solution with water (100ppm)to 100.0mL.

Ferric chloride–sulfamic acid reagent— Prepare a solution containing 10g per Lof ferric chloride and 10g per Lof sulfamic acid.

Acetaldehyde standard solution— Dissolve 1.0g of acetaldehyde in 2-propanol,and dilute with the same solvent to 100.0mL.Dilute 5.0mLof the solution with water to 500.0mL.Prepare immediately before use.

Chlorides— Disperse 250mg in 50mLof water,heat to boiling,and allow to cool,shaking occasionally.Filter,and discard the first 10mLof the filtrate.Dilute 10mLof the filtrate with water to 15mL.Add 1mLofDilute nitric acid,and pour the mixture as a single addition into a test tube containing 1mLof 0.1Nsilver nitrate VS.Prepare a standard in the same manner using 10mLofChloride standard solution and 5mLof water.Examine the tubes laterally against a black background.After standing for 5minutes protected from light,any opalescence in the test solution is not more intense than that in the standard (0.1%).

Dilute nitric acid— Dilute 20mLof nitric acid with water to 100mL.

Chloride standard solution— Immediately before use,dilute with water to 100times its volume a solution containing sodium chloride equivalent to 0.824g per Lof sodium chloride.

Assay—

NOTE—Hydriodic acid and its reaction byproducts are highly toxic.Perform all steps of theTest solution preparation and theReference solution preparation in a properly functioning hood.

Internal standard solution— Dilute 120µLof toluene witho-xylene to 10mL.

Test solution— Transfer 50.0mg of ethylcellulose,50mg of adipic acid,and 2.0mLof theInternal standard solution into a suitable 5mLthick-walled reaction vial with a pressure-tight septum closure.Cautiously add 2.0mLof hydriodic acid,immediately close the vial tightly,and weigh the contents and the vial accurately.Shake the vial for 30seconds,heat to 125

for 10minutes,allow to cool for 2minutes,shake again for 30seconds,and heat to 125

for 10minutes.Afterwards allow to cool for 2minutes,and repeat shaking and heating for a third time.Allow the vial to cool for 45minutes,and reweigh.If the loss is greater than 10mg,discard the mixture and prepare another.Use the upper layer for analysis.

Reference solution— Transfer 100.0mg of adipic acid,4.0mLof theInternal standard solution and 4.0mLof hydriodic acid into a suitable 10mLthick-walled reaction vial with a pressure-tight septum closure.Close the vial tightly,and weigh the vial and contents accurately.Afterwards inject 50µLof the iodoethane through the septum with a syringe,weight the vial again,and calculate the mass of iodoethane added,by difference.Shake well,and allow the layers to separate.

Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 2-mm ×5.0-m stainless steel column packed with 3%G2on 150-µm to 180-µm mesh support S1A.The carrier gas is nitrogen,flowing at a rate of about 15mLper minute.The injection port and detector temperatures are both maintained at 200

.The column temperature is maintained at 80

Procedure— Inject 1µLof the upper layer of theReference solution into the chromatograph,record the chromatogram,and record the areas of the peaks.The relative retention times are as follows:iodoethane 0.6,toluene 1.0,ando-xylene 2.3.Adjust the sensitivity of the system so that the heights of the two principal peaks are at least 50%of the full scale of the recorder.The test is not valid unless the resolution between the peaks corresponding to iodoethane and toluene is at least 2.0.Inject 1µLof theTest solution into the chromatograph,and record the chromatogram as directed for Reference solution.Use the retention times observed in the chromatogram of the Reference solution to identify the peaks in the chromatogram of theTest solution.Calculate the percentage of ethoxy groups by the formula:

[451000/312][Q1m2]/[Q2m1(100–d)],

whereQ1is the ratio of the iodoethane peak area to the toluene peak area in the chromatogram obtained with theTest solution;Q2is the ratio of the iodoethane peak area to the toluene peak area in the chromatogram obtained with theReference solution;m1is the mass of ethylcellulose used in theTest solution in mg;m2is the mass of iodoethane used in theReference solution in mg;andd is the loss on drying as a percentage.

NF23

Auxiliary Information— Staff Liaison:Justin Lane,B.S.,Scientific Associate

Expert Committee:(EMC)Excipients:Monograph Content

USP28–NF23Page 3003

Pharmacopeial Forum:Volume No.30(2)Page 706

Phone Number:1-301-816-8323