Polyvinyl Acetate Phthalate
»Polyvinyl Acetate Phthalate is a reaction product of phthalic anhydride and a partially hydrolyzed polyvinyl acetate.It contains not less than 55.0percent and not more than 62.0percent of phthalyl (o-carboxybenzoyl,C8H5O3)groups,calculated on an anhydrous acid-free basis.
Packaging and storage— Prepare in tight containers.
Identification—
A: The solution prepared for measurement of absorbance in the Assayexhibits a maximum at 277±3nm.
B: To about 10mg contained in a small test tube add 10mg of resorcinol,mix,add 0.5mLof sulfuric acid,and heat in a liquid bath at 160for 3minutes.Cool,and pour the solution into a mixture of 25mLof 1Nsodium hydroxide and 200mLof water:the solution shows a vivid green fluorescence.
C: Dissolve about 2g in 20mLof methanol,and pour 1mLof the solution onto a clear glass plate:a film is deposited as the methanol evaporates.
Viscosity á911ñ— Dissolve a quantity,equivalent to 15g on the anhydrous basis,in 85g of methanol.Determine the viscosity of this solution,using a capillary viscosimeter.The apparent viscosity is between 7and 11centipoises,determined at 25±0.2.
Water,Method Iá921ñ: not more than 5.0%.
Residue on ignition á281ñ: not more than 1.0%.
Free phthalic acid—
Standard preparation— Transfer about 50mg of phthalic anhydride,accurately weighed,to a 1000-mLvolumetric flask,dissolve in water,dilute with water to volume,and mix.
Test preparation— Dissolve about 1500mg of Polyvinyl Acetate Phthalate,accurately weighed,in 50mLof a mixture of methylene chloride and methanol (4:1).Transfer the solution to a separator with the aid of 75mLof water,and swirl,taking care not to shake.Add 100mLof hexanes,shake,and allow the mixture to stand until it separates into 2layers.Transfer the water layer to a 250-mLvolumetric flask.Add 100mLof water to the separator,shake,and allow to stand until the layers separate.Transfer the water layer to the same volumetric flask,dilute with water to volume,and mix.If the solution is cloudy,centrifuge a portion until clear.
Procedure— Concomitantly determine the absorbances of the Standard preparationand the Test preparationin 1-cm cells at the wavelength of maximum absorbance at about 277nm.Calculate the percentage of free phthalic acid taken by the formula:
25(166.13/148.12)(WS/WU)(AU/AS),
in which 166.13and 148.12are the molecular weights of phthalic acid and phthalic anhydride,respectively;WSand WUare the weights,in mg,of phthalic anhydride and Polyvinyl Acetate Phthalate,respectively;and AUand ASare the absorbances of the Test preparationand the Standard preparation,respectively.Not more than 0.6%,on the anhydrous basis,is found.
Free acid other than phthalic— Proceed as directed for Test preparationunder Free phthalic acid,but instead of transferring the water extracts to a volumetric flask,transfer them to a 400-mLbeaker,and titrate with 0.1Nsodium hydroxide VSto a phenolphthalein endpoint.Calculate the volume,Vp,in mL,of 0.1Nsodium hydroxide consumed by the free phthalic acid in the specimen taken by the formula:
(1/830.6)pW,
in which pis the percentage of free phthalic acid,previously determined;and Wis the weight,in mg,of the specimen,on the anhydrous basis.Calculate the percentage of free acid other than phthalic,as acetic acid,taken by the formula:
60.05(10/W)(V-Vp),
in which Vis the total volume,in mL,of 0.1Nsodium hydroxide used.Not more than 0.6%,on the anhydrous basis,is found.
Phthalyl content—
Standard preparation— Transfer 50mg of phthalic anhydride,accurately weighed,to a 1000-mLvolumetric flask,dissolve with heat in 100mLof alcohol,dilute with alcohol to volume,and mix.
Assay preparation— Transfer about 100mg of Polyvinyl Acetate Phthalate,accurately weighed,to a 1000-mLvolumetric flask,dissolve in alcohol,dilute with alcohol to volume,and mix.
Procedure— Concomitantly determine the absorbances of the Standard preparationand the Assay preparationin 1-cm cells at the wavelength of maximum absorbance at about 275nm.Calculate the percentage of phthalyl,on the acid-free basis,taken by the formula:
100(WS/WU)(AU/AS),
in which WSand WUare the weights,in mg,of phthalic anhydride and Polyvinyl Acetate Phthalate on the anhydrous basis,respectively;and AUand ASare the absorbances of the Assay preparationand the Standard preparation,respectively.
Auxiliary Information— Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3064
Phone Number:1-301-816-8262