A: To one portion of the dry residue add 2drops of nitric acid,and evaporate on a steam bath to dryness.Cool and add 10mLof acetone to dissolve the residue.Add a few drops of alcoholic potassium hydroxide TS:a violet color is produced.

B: Dissolve the other portion of the residue in 1mLof 0.1Nhydrochloric acid,and add gold chloride TS,dropwise with shaking,until a definite precipitate separates.Slowly heat until the precipitate dissolves,and allow the solution to cool:lustrous golden yellow scales are formed.

pH9.0Buffer— Dissolve 34.8g of dibasic potassium phosphate in 900mLof water,and adjust to a pHof 9.0,determined electrometrically,by the addition of 3Nhydrochloric acid or 1Nsodium hydroxide,as necessary,with mixing.

Internal standard solution— Dissolve about 25mg of homatropine hydrobromide,accurately weighed,in water contained in a 50-mLvolumetric flask,add water to volume,and mix.Prepare fresh daily.

Standard preparation— Dissolve about 10mg of USP Hyoscyamine Sulfate RS,accurately weighed,in water contained in a 100-mLvolumetric flask,add water to volume,and mix.Prepare fresh daily.Pipet 10.0mLof this solution into a separator,add 2.0mLof Internal standard solutionand 5.0mLof pH9.0Buffer,and adjust with 1Nsodium hydroxide to a pHof 9.0.Extract with two 10-mLportions of methylene chloride,filter the methylene chloride extracts through 1g of anhydrous sodium sulfate supported by a small cotton plug in a funnel into a 50-mLbeaker,and evaporate under nitrogen to dryness.Dissolve the residue in 2.0mLof methylene chloride.

Assay preparation— Weigh and finely powder not less than 20Tablets.Transfer an accurately weighed portion of the powder,equivalent to about 0.86mg of hyoscyamine,to a separator containing 5mLof pH9.0Buffer,and add,by pipet,2.0mLof Internal standard solution.Proceed as directed under Standard preparation,beginning with “adjust with 1Nsodium hydroxide to a pHof 9.0.”

Chromatographic system— Under typical conditions,the instrument contains a 1.8-m ×2-mm glass column packed with 3%liquid phase G3on support S1AB,cured as directed (see Gas Chromatography á621ñ).Maintain the column at 225,and use nitrogen as the carrier gas at a flow rate of 25mLper minute.

System suitability— Chromatograph six to ten injections of the Standard preparation,and record peak areas as directed under Procedure.The analytical system is suitable for conducting this assay if the relative standard deviation for the ratio of the peak areas does not exceed 2.0%,the resolution factor is not less than 5,and the tailing factor does not exceed 2.0.

Procedure— Inject 1-µLportions of the Assay preparationand the Standard preparationsuccessively into the gas chromatograph.Measure the areas under the peaks for hyoscyamine and homatropine in each chromatogram.Calculate the ratio,AU,of the area of the hyoscyamine peak to the area of the internal standard peak in the chromatogram from the Assay preparation,and similarly calculate the ratio,AS,in the chromatogram from the Standard preparation.Calculate the quantity,in mg,ofhyoscyamine (C17H23NO3)in the portion of Tablets taken by the formula: in which 289.37and 676.83are the molecular weights of hyoscyamine and anhydrous hyoscyamine sulfate,respectively,and Wis the weight,in mg,of USP Hyoscyamine Sulfate RStaken for the Standard preparation.