A: Tablets respond to the Identificationtest under Aspirin and Codeine Phosphate Tablets.

B: Tablets respond to the Identificationtests under Alumina and Magnesia Tablets.

Medium: 0.05Macetate buffer,prepared by mixing 2.99g of sodium acetate trihydrate and 1.66mLof glacial acetic acid with water to obtain 1000mLof solution having a pHof 4.50±0.05;900mL.

Apparatus 2: 75rpm.

Time: 30minutes.

Mobile phase,Internal standard solution,Solvent mixture,Aspirinand codeine phosphate standard preparation,Standard solution A,Standard solution B,Standard preparations Aand B,Test preparation,Chromatographic system,and Procedure— Proceed as directed in the test for Dissolutionunder Aspirin and Codeine Phosphate Tablets.

Tolerances— Not less than 75%(Q)of the labeled amounts of aspirin (C9H8O4)and codeine phosphate hemihydrate (C18H21NO3·H3PO4·½H2O)are dissolved in 30minutes.

Mobile phase,Solvent mixture,Salicylic acid stock standard solution,Salicylic acid standard preparation,Aspirinand codeine phosphate standard preparation,andChromatographic system— Prepare as directed in the Assay for aspirin and codeine phosphate and limit of free salicylic acidunder Aspirin and Codeine Phosphate Tablets.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 325mg of aspirin,to a screw-capped,120-mLbottle,add 5.0mLof Internal standard solutionand 45.0mLof Solvent mixture,mix,and sonicate for 2to 5minutes.Centrifuge,and use a portion of the resultant clear solution as the Assay preparation.

Procedure— Separately inject equal volumes (about 5µL)of the Salicylic acid standard preparation,the Aspirin and codeine phosphate standard preparation,and the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times for salicylic acid,aspirin,codeine,and phenacetin are about 0.3,0.5,0.8,and 1.0,respectively.Calculate the quantity,in mg,of aspirin (C9H8O4)in the portion of powdered Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Aspirin RSin the Aspirin and codeine phosphate standard preparation;and RUand RSare the ratios of the peak responses of aspirin and phenacetin obtained from the Assay preparationand the Aspirin and codeine phosphate standard preparation,respectively.Calculate the quantity,in mg,of codeine phosphate hemihydrate (C18H21NO3·H3PO4·½H2O),in the portion of powdered Tablets taken by the formula: in which 406.37and 397.37are the molecular weights of codeine phosphate hemihydrate and anhydrous codeine phosphate,respectively;Cis the concentration,in mg per mL,of USP Codeine Phosphate RSin the Aspirin and codeine phosphate standard preparation;and RUand RSare the ratios of the peak responses of codeine phosphate and phenacetin obtained from the Assay preparationand the Aspirin and codeine phosphate Standard preparation,respectively.Calculate the percentage of free salicylic acid in the Tablets taken by the formula: in which Cis the concentration,in mg per mL,of USP Salicylic Acid RSin the Salicylic acid standard preparation;a is the quantity,in mg,of aspirin in the portion of Tablets taken,determined as directed above;and RUand RSare the ratios of the peak responses of salicylic acid and phenacetin obtained from the Assay preparationand the Salicylic acid standard preparation,respectively:not more than 3.0%is found.

Edetate disodium titrant— Prepare and standardize as directed in the Assayunder Ammonium Alum.

Assay preparation— Weigh and finely powder not fewer than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 600mg of aluminum hydroxide,to a 150-mLbeaker,add 20mLof water,stir,and slowly add 30mLof 3Nhydrochloric acid.Heat gently,if necessary,to aid solution,cool,and filter into a 200-mLvolumetric flask.Wash the filter with water into the flask,add water to volume,and mix.

Procedure— Pipet 10mLof Assay preparationinto a 250-mLbeaker,add 20mLof water,then add,in the order named and with continuous stirring,25.0mLof Edetate disodium titrantand 20mLof acetic acid-ammonium acetate buffer TS.Add 50mLof alcohol and 2mLof dithizone TS,and mix.Titrate with 0.05Mzinc sulfate VSuntil the color changes from green-violet to rose-pink.Perform a blank determination,substituting 10mLof water for the Assay preparation,and make any necessary correction.Each mLof 0.05M Edetate disodium titrant is equivalent to 3.900mg of Al(OH)3.

Assay preparation— Prepare as directed in the Assay for aluminum oxide.

Procedure— Pipet a volume of Assay preparation,equivalent to about 40mg of magnesium hydroxide,into a 400-mLbeaker,add 200mLof water and 20mLof triethanolamine,and stir.Add 10mLof ammonia-ammonium chloride buffer TSand 3drops of an eriochrome black indicator solution prepared by dissolving 200mg of eriochrome black Tin a mixture of 15mLof triethanolamine and 5mLof dehydrated alcohol,and mix.Cool the solution to between 3and 4by immersion of the beaker in an ice bath,then remove,and titrate with 0.05Medetate disodium VSto a blue endpoint.Perform a blank determination,substituting 10mLof water for the Assay preparation,and make any necessary correction.Each mLof 0.05Medetate disodium consumed is equivalent to 2.916mg of Mg(OH)2.