A: Infrared Absorption á197Mñ.

B: It responds to the tests for Sodium á191ñ.

Internal standard solution— Dissolve 75mg of N,N-diethylaniline in 25mLof 1Nhydrochloric acid,and dilute quantitatively and stepwise with water to obtain a solution containing about 30µg per mL.

Standard preparation— Transfer 50.0mg of N,N-dimethylaniline to a 50-mLvolumetric flask,add 25mLof 1Nhydrochloric acid,swirl to dissolve,dilute with water to volume,and mix.Transfer 2.0mLof the resulting solution to a 100-mLvolumetric flask,dilute with water to volume,and mix.To a suitable centrifuge tube add 1.0mLof this solution,1.0mLof 1.25Nsodium hydroxide,1.0mLof Internal standard solution,and 1.0mLof cyclohexane,shake vigorously for 1minute,and centrifuge.Use the clear supernatant as the Standard preparation.

Test preparation— Transfer 1.0g of Ampicillin Sodium to a suitable centrifuge tube,add 2mLof 1.25Nsodium hydroxide,swirl to dissolve the specimen,add 1.0mLof Internal standard solutionand 1.0mLof cyclohexane,shake vigorously for 1minute,and centrifuge.Use the clear supernatant as the Test preparation.

Internal standard solution— Prepare a solution of dioxane in dimethyl sulfoxide containing about 2.1mg per mL.

Standard solution— Dissolve an accurately weighed quantity of methylene chloride in Internal standard solutionto obtain a solution having a known concentration of about 0.33mg per mL.

Test solution— Dissolve about 500mg of Ampicillin Sodium,accurately weighed,in 3.0mLof Internal standard solution.

Chromatographic system(see Chromatography á621ñ)— The gas chromatograph is equipped with a flame-ionization detector and a 1.8-m ×4-mm glass column packed with a 10%phase G39on unsilanized support S1A.The column temperature is maintained at 65,and the injection port and the detector block temperatures are maintained at about 100and 260,respectively.Nitrogen is used as the carrier gas at a flow rate of about 60mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the relative retention times are about 0.5for methylene chloride and 1.0for dioxane;the resolution,R,between the methylene chloride peak and the dioxane peak is not less than 4;and the relative standard deviation for replicate injections is not more than 5%.

Procedure— Separately inject equal volumes (about 1µL)of the Standard solutionand the Test solutioninto the chromatograph,record the chromatograms,and measure the responses for the methylene chloride and dioxane peaks.Calculate the percentage of methylene chloride in the portion of Ampicillin Sodium taken by the formula: in which Cis the concentration,in mg per mL,of methylene chloride in the Standard solution;mis the quantity,in mg,of Ampicillin Sodium taken to prepare the Test solution;and RUand RSare the ratios of the response of the methylene chloride peak to that of the dioxane peak obtained from the Test solutionand the Standard solution,respectively.The limit is 0.2%.

Mobile phase,Diluent,Standard preparation,Resolution solution,and Chromatographic system— Prepare as directed in the Assayunder Ampicillin.

Assay preparation— [NOTE—Ampicillin Sodium is hygroscopic.Minimize exposure to the atmosphere,and weigh promptly.]Transfer an accurately weighed quantity of Ampicillin Sodium,equivalent to about 100mg of anhydrous ampicillin,to a 100-mLvolumetric flask,dissolve in and dilute with Diluentto volume,and mix.Use this solution promptly after preparation.

Procedure— Proceed as directed for Procedurein the Assayunder Ampicillin.Calculate the quantity,in µg,of ampicillin (C16H19N3O4S)in each mg of Ampicillin Sodium taken by the formula: in which Wis the weight,in mg,of Ampicillin Sodium taken to prepare the Assay preparation;and the other terms are as defined in the Assayunder Ampicillin.