Standard preparation— Pipet 5mLof dehydrated alcohol and 5mLof acetone into a 200-mLvolumetric flask containing 50mLof water,add water to volume,and mix.Pipet 10mLof this solution into a 200-mLvolumetric flask,add water to volume,and mix.

Test preparation— Transfer an accurately measured volume of Oral Solution,equivalent to about 5mLof alcohol,to a 200-mLvolumetric flask containing about 30mLof water.Pipet 5mLof acetone into the flask,add water to volume,and mix.Pipet 10mLof this solution into a 200-mLvolumetric flask,add water to volume,and mix.

Chromatographic system— The gas chromatograph is equipped with a flame-ionization detector and contains a 75-cm ×4-mm column packed with 20%phase G20on support S1AB,conditioned as directed (see Chromatography á621ñ).The column is maintained at a temperature of about 85,and the injection port and detector block are maintained at about 175and 225,respectively.Nitrogen is used as the carrier gas at a flow rate of about 18mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,is not less than 2.0;the tailing factor of the alcohol peak is not greater than 1.5;and the relative standard deviation for replicate injections is not more than 2.0%in the ratio of the peak of alcohol to the peak of acetone.

Procedure— Separately inject equal volumes (about 4µL)of the Test preparationand the Standard preparation,in duplicate,into the gas chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the percentage of alcohol in the specimen taken by the formula: in which Vis the volume,in mL,of Oral Solution taken,and RUand RSare the peak response ratios of alcohol to that of acetone obtained from the Assay preparationand the Standard preparation,respectively:the alcohol content,obtained as the average of the calculated results,is between 90.0%and 110.0%of the labeled amount of C2H5OH.

Mobile phase andChromatographic system— Prepare as directed in the Assayunder Dyphylline Tablets.

Standard preparation— Dissolve an accurately weighed quantity of USP Dyphylline RSin Mobile phaseto obtain a solution having a known concentration of about 500µg per mL.

Assay preparation— Transfer an accurately measured volume of Oral Solution,equivalent to about 100mg of dyphylline,to a 200-mLvolumetric flask,add Mobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 10µL),of the Standard preparationand the Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.Calculate the quantity,in mg,of dyphylline (C10H14N4O4)in the volume of Oral Solution taken by the formula: in which Cis the concentration,in µg per mL,of USP Dyphylline RSin the Standard preparation;and rUand rSare the dyphylline peak responses obtained from the Assay preparationand the Standard preparation,respectively.

(Official June 1,2005)