Ammonium bicarbonate solution,Diluent,Solution A,Solution B,Mobile phase,Internal standard solution,and Chromatographic system— Proceed as directed in the Assayunder Dimenhydrinate Tablets.

Standard solution— Prepare as directed for Standard preparationin the Assayunder Dimenhydrinate Tablets.

Test solution— Prepare as directed for Assay preparationin the Assay.

Procedure— Separately inject equal volumes (about 10µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg per mL,of 8-chlorotheophylline (C7H7ClN4O2)in the portion of Syrup taken by the formula: in which 214.61and 469.96are the molecular weights of 8-chlorotheophylline and dimenhydrinate,respectively;Wis the weight,in mg,of USP Dimenhydrinate RSin the Standard solution;and RUand RSare peak area ratios of 8-chlorotheophylline to the internal standard obtained from the Test solutionand the Standard solution,respectively.An amount of 8-chlorotheophylline that is between 43.4%and 47.9%of the amount of dimenhydrinate is found.

Ammonium bicarbonate solution,Diluent,Solution A,Solution B,Mobile phase,Internal standard solution,Standard preparation,and Chromatographic system— Proceed as directed in the Assayunder Dimenhydrinate Tablets.

Assay preparation— Pipet 5.0mLof Syrup into a suitable container,add 5.0mLof Internal standard solution,and mix.Transfer about 1mLof this solution to a suitable container,add about 5mLofDiluent,and mix.

Procedure— Proceed as directed for Procedurein the Assayunder Dimenhydrinate Tablets.Calculate the quantity,in mg per mL,of dimenhydrinate (C17H21NO·C7H7ClN4O2)in the portion of the Syrup taken by the formula: in which Wis the weight,in mg,of USP Dimenhydrinate RSin the Standard preparation;and RUand RSare the peak area ratios of diphenhydramine to the internal standard obtained from the Assay preparationand the Standard preparation,respectively.