A: Infrared Absorption 197K.

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

Solution A— Dissolve 6.9 g of monobasic ammonium phosphate in 1960 mL of water. Adjust with phosphoric acid to a pH of 2.5, add 40 mL of acetonitrile, and mix. Filter, if necessary, to obtain a clear solution, and degas.

Solution B— Dissolve 6.9 g of monobasic ammonium phosphate in 600 mL of water. Adjust with phosphoric acid to a pH of 2.5, add 1400 mL of acetonitrile, and mix. Filter, if necessary, to obtain a clear solution, and degas.

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system.

note—When preparing the System suitability solution, the Standard solution, and the Test solution, if necessary, sonicate and mix on a vortex mixer to aid in dissolution. Use the solutions immediately after preparation or refrigerate and use within 24 hours.

Phenylglycine solution— Dissolve an accurately weighed quantity of phenylglycine in Solution A to obtain a solution having a known concentration of about 0.0075 mg per mL.

System suitability solution— Dissolve accurately weighed quantities of USP Loracarbef RS and USP Cefaclor RS in Solution A to obtain a solution having known concentrations of about 0.01 mg of each per mL.

Standard solution— Dissolve an accurately weighed quantity of USP Loracarbef RS in Solution A to obtain a solution having a known concentration of about 0.01 mg per mL.

Test solution— Transfer about 50 mg of Loracarbef, accurately weighed, to a 10-mL volumetric flask, add about 8 mL of Solution A, and dissolve. Dilute with Solution A to volume, and mix. Filter, if necessary, to obtain a clear solution.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 220-nm detector and a 4.6-mm × 15-cm column that contains 5-µm packing L1. The flow rate is about 2 mL per minute, and is maintained at a constant temperature of about 40. The chromatograph is programmed as follows. Initially it is equilibrated with Solution A, then the proportion of Solution B is increased linearly from 0% to 14.5% over 9.5 minutes, then increased from 14.5% to 100% over 7.5 minutes, and held at 100% for an additional 1.5 minutes. Finally, the composition of the Mobile phase is changed to 100% Solution A, and is allowed to re-equilibrate for about 4 minutes or until a stable baseline is obtained. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.9 for cefaclor and 1.0 for loracarbef; the resolution, R, between the cefaclor peak and the loracarbef peak is between 4.0 and 8.0; and the tailing factor for the loracarbef peak is not more than 1.3. Calculate the recovery of loracarbef from the System suitability solution by the formula: in which C is the concentration, in mg per mL, of USP Loracarbef RS in the Standard solution; L is the concentration, in mg per mL, of USP Loracarbef RS in the System suitability solution; and rL and rS are the loracarbef responses in the chromatograms obtained from the System suitability solution and the Standard solution, respectively: the recovery is between 95% and 105%.

Procedure— Separately inject equal volumes (about 20 µL) of Solution A, the Phenylglycine solution, the Standard solution, and the Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Disregard any peak responses in the chromatograms that correspond to those in the chromatogram obtained from Solution A, and identify any peak in the chromatogram of the Test solution that corresponds to the peak for phenylglycine in the chromatogram obtained from the Phenylglycine solution. Separately calculate the percentage of each related compound in the portion of Loracarbef taken by the formula: in which Y is the concentration, in mg per mL, of Loracarbef in the Test solution; rY is the response of any related compound in the chromatogram obtained from the Test solution; and C and rS are as defined above: not more than 0.15% of phenylglycine is found, not more than 0.5% of any other related compound is found, and the sum of all other related compounds is not more than 2.0%.

Mobile phase— Dissolve 2.0 g of sodium 1-pentanesulfonate in 1560 mL of water, add 20 mL of triethylamine, and adjust with phosphoric acid to a pH of 2.5. Add 440 mL of methanol, mix, and pass through a filter having a porosity of 0.5 µm or finer, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Transfer about 10 mg of USP Loracarbef RS, accurately weighed, to a 50-mL volumetric flask, dissolve in Mobile phase, using sonication, if necessary, to achieve dissolution, dilute with Mobile phase to volume, and mix.

Assay preparation— Transfer about 10 mg of Loracarbef, accurately weighed, to a 50-mL volumetric flask, dissolve in Mobile phase, using sonication, if necessary, to achieve dissolution, dilute with Mobile phase to volume, and mix.

Resolution solution— Prepare a solution in Mobile phase containing about 0.2 mg each of USP Loracarbef RS and of USP Loracarbef L-Isomer RS in each mL.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 265-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the Resolution solution, and record the responses as directed for Procedure: the relative retention times are about 0.6 for loracarbef l-isomer and 1.0 for loracarbef; and the resolution, R, between the loracarbef l-isomer peak and the loracarbef peak is not less than 6.0. Chromatograph the Standard preparation, and record the responses as directed for Procedure: the capacity factor for the loracarbef peak is not less than 5 and not more than 8; the tailing factor is not less than 0.8 and not more than 1.3; the column efficiency, determined from the loracarbef peak, is not less than 2500 theoretical plates; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— [note—Use peak areas where peak responses are indicated.] Separately inject equal volumes (about 20 µL) of the Standard preparation and the Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in µg, of anhydrous loracarbef (C16H16ClN3O4) in each mg of the Loracarbef taken by the formula: in which W is the quantity, in mg, of USP Loracarbef RS taken to prepare the Standard preparation; P is the assigned potency, in µg of anhydrous loracarbef (C16H16ClN3O4) in each mg of USP Loracarbef RS; w is the quantity, in mg, of Loracarbef taken to prepare the Assay preparation; and rU and rS are the loracarbef peak responses obtained from the Assay preparation and the Standard preparation, respectively.