A: Infrared Absorption 197K—

B: The retention times of the cefprozil (Z)-isomer and cefprozil (E)-isomer peaks in the chromatogram of the Assay preparation correspond to those of the Standard preparations, as obtained in the Assay.

E / (E + Z),

(Official January 1, 2007)

Mobile phase— Dissolve 20.7 g of monobasic ammonium phosphate in 1800 mL of water, and adjust, if necessary, with phosphoric acid to a pH of 4.4. Add 200 mL of acetonitrile, and mix. Filter this solution through a filter having a porosity of 0.5 µm or finer, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621. [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 0.25 mg per mL. [NOTE—Use this solution within 6 hours.]

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 0.25 mg per mL. Transfer 5.0 mL of this stock solution to a 50-mL volumetric flask, dilute with water to volume, and mix. [NOTE—Use this solution within 6 hours.]

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 6 hours.]

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

Chromatographic system (see Chromatography 621)—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 1 mL per minute. Chromatograph the Resolution solution, and record the responses as directed under Procedure: the relative retention times are about 0.7 for cefprozil (Z)-isomer and 1.0 for 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 2500 theoretical plates when calculated by the formula: the tailing factor, determined from the cefprozil (Z)-isomer peak, is not less than 0.9 and not more than 1.1, when calculated by the formula: in which W0.1 is 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 10 µL) of the Cefprozil (Z)-isomer standard preparation, the Cefprozil (E)-isomer standard preparation, and the Assay preparation into 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 C is the concentration, in mg per mL, of USP Cefprozil (Z)-Isomer RS in the Cefprozil (Z)-isomer standard preparation or of the USP Cefprozil (E)-Isomer RS in the Cefprozil (E)-isomer standard preparation, as appropriate; P is the assigned potency, in µg per mg, of the appropriate USP Reference Standard; M is the quantity, in mg, of Cefprozil taken to prepare the Assay preparation; and rU and rS are the peak responses of the cefprozil (Z)-isomer or the cefprozil (E)-isomer, as appropriate, obtained from the Assay preparation and 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.