Methylcellulose

Cellulose,methyl ether.
Cellulose methyl ether [9004-67-5].
»Methylcellulose is a methyl ether of cellulose.When dried at 105for 2hours,it contains not less than 27.5percent and not more than 31.5percent of methoxy (OCH3)groups.
Packaging and storage— Preserve in well-closed containers.
Labeling— Label it to indicate its viscosity type [viscosity of a solution (1in 50)].
Identification—
A: Gently add 1g to the top of 100mLof water in a beaker,and allow to disperse over the surface,tapping the top of the container to ensure an even dispersion of the test specimen.Allow the beaker to stand until the specimen becomes transparent and mucilaginous (about 5hours),and swirl the beaker to wet the remaining substance,add a stirring bar,and stir until solution is complete:the mixture remains stable when an equal volume of 1Nsodium hydroxide or 1Nhydrochloric acid is added.
B: Heat a few mLof the solution prepared for Identificationtest A:the solution becomes cloudy and a flaky precipitate,which redissolves as the solution cools,appears.
C: Pour a few mLof the solution prepared for Identificationtest Aonto a glass plate,and allow the water to evaporate:a thin,self-sustaining film results.
Apparent viscosity— Place a quantity,accurately weighed and equivalent to 2g of solids on the dried basis,in a tared,wide-mouth 250-mLcentrifuge bottle,and add 98g of water previously heated to 80to 90.Stir with a propeller-type stirrer for 10minutes,place the bottle in an ice-bath,continue the stirring,and allow to remain in the ice-bath for 40minutes to ensure that hydration and solution are complete.Adjust the weight of the solution to 100g,if necessary,and centrifuge the solution to expel any entrapped air.Adjust the temperature of the solution to 20±0.1,and determine the viscosity in a suitable viscosimeter of the Ubbelohde type as directed for Procedure for Cellulose Derivativesunder Viscosity á911ñ.Its viscosity is not less than 80.0%and not more than 120.0%of that stated on the label for viscosity types of 100centipoises or less,and not less than 75.0%and not more than 140.0%of that stated on the label for viscosity types higher than 100centipoises.
Loss on drying á731ñ— Dry it at 105for 2hours:it loses not more than 5.0%of its weight.
Residue on ignition á281ñ: not more than 1.5%.
Heavy metals,Method IIá231ñ: 0.001%,adding 1mLof hydroxylamine hydrochloride solution (1in 5)to the solution of the residue.
Organic volatile impurities,Method Vá467ñ: meets the requirements.
Solvent— Use dimethyl sulfoxide.
Assay— [Caution—Perform all steps involving hydriodic acid carefully,in a well-ventilated hood.Use goggles,acid-resistant gloves,and other appropriate safety equipment.Be exceedingly careful when handling the hot vials,since they are under pressure.In the event of hydriodic exposure,wash with copious amounts of water,and seek medical attention at once.]
Hydriodic acid— Use a reagent having a specific gravity of at least 1.69,equivalent to 55%HI.
Internal standard solution— Transfer about 2.5g of toluene,accurately weighed,to a 100-mLvolumetric flask containing 10mLof o-xylene,dilute with o-xylene to volume,and mix.
Standard preparation— Into a suitable serum vial weigh about 135mg of adipic acid,add 4.0mLof Hydriodic acid,then pipet 4mLof Internal standard solutioninto the vial,and close the vial securely with a suitable septum stopper.Weigh the vial and contents accurately,add 90µLof methyl iodide with a syringe through the septum,again weigh,and calculate the weight of methyl iodide added,by difference.Shake,and allow the layers to separate.
Assay preparation— Transfer about 0.065g of dried Methylcellulose,accurately weighed,to a 5-mLthick-walled reaction vial equipped with a pressure-tight septum closure,add an amount of adipic acid equal to the weight of the test specimen,and pipet 2mLof Internal standard solutioninto the vial.Cautiously pipet 2mLof Hydriodic acidinto the mixture,immediately secure the closure,and weigh it accurately.Shake the vial for 30seconds,heat at 150for 20minutes,using a heating block or a protective wrapping,remove it from the source of heat,shake it again,using extreme caution,and heat it as before at 150for an additional 40minutes.Allow the vial to cool for about 45minutes,and again weigh it.If the weight loss is greater than 10mg,discard the mixture,and prepare another Assay preparation.
Chromatographic system— Use a gas chromatograph equipped with a thermal conductivity detector.Under typical conditions,the instrument contains a 1.8-m ×4-mm glass column packed with 10%liquid phase G1on 100-to 120-mesh support S1A,the column is maintained at 100,the injection port and the detector are maintained at 200,and helium is used as the carrier gas at a flow rate of 20mLper minute.
Calibration— Inject about 2µLof the upper layer of the Standard preparationinto the gas chromatograph,and record the chromatogram.The retention times for methyl iodide,toluene,and o-xylene are approximately 3,7,and 13minutes,respectively.Calculate the relative response factor,Fmi,of equal weights of toluene and methyl iodide taken by the formula:
Qsmi/Asmi,
in which Qsmiis the quantity ratio of methyl iodide to toluene in the Standard preparation,and Asmiis the peak area ratio of the methyl iodide to toluene obtained from the Standard preparation.
Procedure— Inject about 2µLof the upper layer of the Assay preparationinto the gas chromatograph,and record the chromatogram.Calculate the percentage of methoxy in the Methylcellulose taken by the formula:
2(31/142)FmiAumi(Wt/Wu),
in which 31/142is the ratio of the formula weights of methoxy and methyl iodide;Fmiis defined under Calibration,Aumiis the ratio of the area of the methyl iodide peak to that of the toluene peak obtained from the Assay preparation;Wtis the weight,in g,of toluene in the Internal standard solution;and Wuis the weight,in g,of Methylcellulose taken for the Assay.
Auxiliary Information— Staff Liaison:Justin Lane,B.S.,Scientific Associate
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 1257
Phone Number:1-301-816-8323