A: Infrared Absorption á197Kñ.

B: The retention time of the major peak in the chromatogram of the Assay preparationcorresponds to that in the chromatogram of the Standard preparation,as obtained in the Assay.

Test solution: 10mg per mL,in dimethylformamide.

pH7.5buffer— Dissolve 4.08g of monobasic potassium phosphate in 800mLof water,adjust with 1Nsodium hydroxide to a pHof 7.5±0.1,dilute with water to 1000mL,and mix.

Mobile phase— Prepare a suitable filtered and degassed mixture of pH7.5buffer and methanol (750:250).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Resolution solutionand Chromatographic system— Proceed as directed in theAssay.

Standard solution— Transfer about 15mg of sodium 5-mercapto-1-methyltetrazole and 25mg ofUSP Cefpiramide RS,both accurately weighed,to a 100-mLvolumetric flask,dissolve in and dilute withpH7.5bufferto volume,and mix.Transfer 2.0mLof this solution to a second 100-mLvolumetric flask,dilute withMobile phaseto volume,and mix.This solution contains about 3µg of sodium 5-mercapto-1-methyltetrazole and about 5µg ofUSP Cefpiramide RSper mL.

Test solution— Transfer about 25mg of Cefpiramide,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute withMobile phaseto volume,and mix.

Procedure— Separately inject equal volumes (about 20µL)of theStandard solutionand theTest solutioninto the chromatograph,record the chromatograms,and measure the areas for all of the peaks.Calculate the percentage of 5-mercapto-1-methyltetrazole in the portion of Cefpiramide taken by the formula: in which 115.14and 138.13are the molecular weights of 5-mercapto-1-methyltetrazole and anhydrous sodium 5-mercapto-1-methyltetrazole,respectively;Ctis the concentration,in µg per mL,of sodium 5-mercapto-1-methyltetrazole in theStandard solution;wis the percentage of water,determined by the titrimetric method (See Water Determination á921ñ,but prepare theTest Preparation as follows.Transfer about 100mg of sodium 5-mercapto-1-methyltetrazole,accurately weighed,to a stoppered centrifuge tube.Add 10.0mLof a solution of N-ethylmaleimide in methanol (4in 100),and sonicate for 15minutes.Titrate 5.0mLof this Test Preparation.)in the sodium 5-mercapto-1-methyltetrazole taken to prepare the Standard solution;Wis the weight,in mg,of Cefpiramide taken to prepare the Test solution;andrUandrSare the 5-mercapto-1-methyltetrazole peak responses obtained from theTest solutionand theStandard solution,respectively:not more than 0.7%of 5-mercapto-1-methyltetrazole is found.Calculate the percentage of each other impurity in the portion of Cefpiramide taken by the formula: in which Cis the concentration,in µg per mL,ofUSP Cefpiramide RSin theStandard solution;Eis the designated cefpiramide content,in µg per mg,ofUSP Cefpiramide RS;Wis the weight,in mg,of Cefpiramide taken to prepare theTest solution;rUis the response of each other impurity obtained from theTest solution;andrSis the cefpiramide peak response obtained from theStandard solution:not more than 0.7%of any other individual impurity is found.The total of the percentages of 5-mercapto-1-methyltetrazole and all other impurities is not more than 2.0%.

pH6.8buffer— Dissolve 1.36g of monobasic potassium phosphate in 900mLof water,adjust with 1Nsodium hydroxide to a pHof 6.8±0.1,dilute with water to 1000mL,and mix.

Mobile phase— Prepare a suitable filtered and degassed mixture ofpH6.8buffer,acetonitrile,tetrahydrofuran,and methanol (900:20:60:20).Make adjustments if necessary (seeSystem Suitability underChromatography á621ñ).

Resolution solution— Prepare a solution ofUSP Cefpiramide RSin 0.01Nsodium hydroxide containing about 1mg per mL.Heat this solution at 95for 10minutes.Mix 1mLof this solution with 19mLofMobile phase.This solution contains a mixture of cefpiramide and cefpiramide lactone.

Standard preparation— Dissolve an accurately weighed quantity ofUSP Cefpiramide RSinMobile phaseto obtain a solution having a known concentration of about 0.25mg per mL.

Assay preparation— Transfer about 50mg of Cefpiramide,accurately weighed,to a 200-mLvolumetric flask,dissolve in and dilute withMobile phaseto volume,and mix.

Chromatographic system(seeChromatography á621ñ)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×25-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph theResolution solution,and record the peak responses as directed forProcedure:the relative retention times are about 0.7for cefpiramide and 1.0for cefpiramide lactone,and the resolution between the cefpiramide lactone peak and the cefpiramide peak is not less than 5.Chromatograph theStandard preparation,and record the peak responses as directed forProcedure:the capacity factor,k¢,is between 2and 5and the column efficiency is not less than 1700theoretical plates when calculated by the formula: the tailing factor for the cefpiramide peak is not less than 0.95and not more than 1.4,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of theStandard preparation and theAssay preparation into the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in µg,of C25H24N8O7S2in each mg of the Cefpiramide taken by the formula: in which Cis the concentration,in mg per mL,ofUSP Cefpiramide RSin theStandard preparation;Eis the designated cefpiramide (C25H24N8O7S2)content,in µg per mg,ofUSP Cefpiramide RS;Wis the weight,in mg,of the Cefpiramide taken to prepare theAssay preparation;andrUandrSare the cefpiramide peak responses obtained from theAssay preparation and theStandard preparation,respectively.