A: Infrared Absorption á197Kñ—

B: The retention times of the cefprozil (Z)-isomer and cefprozil (E)-isomer peaks in the chromatogram of the Assay preparationcorrespond to those of the Standard preparationsas obtained in the Assay.

E/(E+Z),

Mobile phase— Dissolve 20.7g of monobasic ammonium phosphate in 1800mLof water,and adjust,if necessary,with phosphoric acid to a pHof 4.4.Add 200mLof acetonitrile,and mix.Filter this solution through a filter having a porosity of 0.5µm or finer,and degas.Make adjustments if necessary (see System Suitability under Chromatography á621ñ.[NOTE—Decreasing the proportion of acetonitrile increases retention times and improves the separation of the cefprozil isomer peaks.]

Standard cefprozil (Z)-isomer preparation—Dissolve an accurately weighed quantity of USP Cefprozil (Z)-Isomer RS.quantitatively in water to obtain a solution having a known concentration of about 0.25mg per mL.[NOTE—Use this solution within 6hours.]

Standard cefprozil (E)-isomer preparation—Dissolve an accurately weighed quantity of USP Cefprozil (E)-Isomer RS.quantitatively in water to obtain a stock solution having a known concentration of about 0.25mg per mL.Transfer 5.0mLof this stock solution to a 50-mLvolumetric flask,dilute with water to volume,and mix.[NOTE—Use this solution within 6hours.]

Resolution solution— Prepare a mixture of equal volumes of the Cefprozil(Z)-isomer standard preparation and of the stock solution used to prepare the Cefprozil(E)-isomer standard preparation.[NOTE—Use this solution within 6hours.]

Assay preparation— Transfer about 15mg of Cefprozil,accurately weighed,to a 50-mLvolumetric flask,dilute with water to volume,and shake to assure dissolution.[NOTE—Use this solution within 6hours.]

Chromatographic system (see Chromatography á621ñ)—The liquid chromatograph is equipped with a 280-nm detector and a 3.9-mm ×25-cm column that contains 5-µm packing L1.The flow rate is about 1mLper minute.Chromatograph the Resolution solution,and record the responses as directed under Procedure:the relative retention times are about 0.7for cefprozil (Z)-isomer and 1.0for cefprozil (E)-isomer,and the resolution,R,between the cefprozil (Z)-isomer peak and the cefprozil (E)-isomer peak is not less than 2.5.Chromatograph the Cefprozil(Z)-isomer standard preparation,and record the responses as directed under Procedure:the column efficiency,determined from the cefprozil (Z)-isomer peak,is not less than 2500theoretical plates when calculated by the formula: the tailing factor,determined from the cefprozil (Z)-isomer peak,is not less than 0.9and not more than 1.1,when calculated by the formula: in which W0.1is the width of the peak at 10%height,and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 10µL)of the Cefprozil(Z)-isomer standard preparation,the Cefprozil(E)-isomer standard preparation,and the Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in µg,of cefprozil (Z)-isomer and cefprozil (E)-isomer in each mg of the Cefprozil taken by the formula: in which Cis the concentration,in mg per mL,of USP Cefprozil (Z)-Isomer RSin the Cefprozil(Z)-isomer standard preparation or of the Cefprozil (E)-Isomer RSin the Cefprozil(E)-isomer standard preparation,as appropriate,Pis the assigned potency,in µg per mg,of the appropriate USP Reference Standard,Mis the quantity,in mg,of Cefprozil taken to prepare the Assay preparation,and rUand rSare the peak responses of the cefprozil (Z)-isomer or the cefprozil (E)-isomer,as appropriate,obtained from the Assay preparationand the relevant Standard preparation,respectively.Calculate the quantity,in µg,of cefprozil (C18H19N3O5S)in each mg of the Cefprozil taken by adding the values,in µg per mg,obtained for the cefprozil (Z)-isomer and for cefprozil (E)-isomer.