A: Infrared Absorption 197K. [note—If a difference appears in the IR spectra of the analyte and the Standard, dissolve equal portions of the test specimen and the USP Reference Standard in equal volumes of methanol. Evaporate the solutions to dryness on a steam bath, protecting the solutions from light, and dry at 105 for 30 minutes. Repeat the test on the residues.]

B: A solution (0.2 in 1) meets the requirements of the flame test for Sodium 191.

Solution A, Solution B, and Mobile phase— Proceed as directed in the Assay.

System suitability solution— Prepare a solution in a mixture of methanol and acetonitrile (3:2) containing about 0.1 mg of USP Fluvastatin Related Compound B RS per mL. Transfer about 0.5 mL of this solution to a 10-mL volumetric flask, and dilute to volume with the System suitability preparation, prepared as directed in the Assay. [note—The System suitability solution is stable for up to 6 months if stored in a refrigerator.]

Standard solution— Use the Standard preparation, prepared as directed in the Assay.

Test solution— Use the Assay preparation, prepared as directed in the Assay.

Chromatographic system— Proceed as directed in the Assay, except use the liquid chromatograph equipped with either a programmable variable wavelength detector or two separate detectors capable of monitoring at 305 nm and at 365 nm. Chromatograph the System suitability solution, and record the peak responses at 305 nm as directed for Procedure. Identify the peaks corresponding to fluvastatin, fluvastatin anti-isomer, and fluvastatin t-butyl ester. The resolution, R, between fluvastatin anti-isomer and fluvastatin is not less than 1.6; the column efficiency is not less than 700 theoretical plates for the fluvastatin peak; and the tailing factor is not more than 3.0. Chromatograph the Standard solution, and record the peak responses at 305 nm as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— Separately inject equal volumes (about 20 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms at 305 nm and 365 nm, identify the impurities listed in Table 1, and measure the peak responses. [note—3-Hydroxy-5-keto fluvastatin is monitored using a wavelength of 365 nm, and all other compounds are monitored at 305 nm.] Calculate the percentage of each impurity, except for 3-hydroxy-5-keto fluvastatin, in the portion of Fluvastatin Sodium taken by the formula: in which F is the relative response factor as listed in Table 1 [note—Use F equal to 1.0 for unknown impurities]; CS is the concentration, in mg per mL, of USP Fluvastatin Sodium RS in the Standard solution; CT is the concentration, in mg per mL, of Fluvastatin Sodium in the Test solution; ri (305) is the peak response at 305 nm for each impurity obtained from the Test solution; and rS (305) is the peak response at 305 nm for the fluvastatin peak obtained from the Standard solution.

Solution A— Add 20 mL of 25% aqueous tetramethylammonium hydroxide solution to 880 mL of water. Adjust with about 2.3 mL of phosphoric acid to a pH of 7.2 ± 0.2. Add 100 mL of a mixture of methanol and acetonitrile (3:2), mix, and filter.

Solution B— Add 20 mL of 25% aqueous tetramethylammonium hydroxide solution and 80 mL of water to 900 mL of a mixture of methanol and acetonitrile (3:2). Adjust with about 2.3 mL of phosphoric acid to a pH of 7.2 ± 0.2, mix, and filter. Make adjustments if necessary (see System Suitability under Chromatography 621).

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

System suitability preparation— Transfer an accurately weighed quantity of USP Fluvastatin for System Suitability RS to a suitable volumetric flask, dissolve first in Solution B, using 40% of the final volume, then dilute with Solution A to volume, and mix to obtain a solution having a known concentration of about 0.5 mg of fluvastatin sodium per mL.

Standard preparation— Transfer an accurately weighed quantity of USP Fluvastatin Sodium RS to a suitable volumetric flask, dissolve first in Solution B, using 40% of the final volume, then dilute with Solution A to volume, and mix to obtain a solution having a known concentration of about 0.5 mg of fluvastatin sodium per mL.

Assay preparation— Transfer about 25 mg of Fluvastatin Sodium, accurately weighed, to a 50-mL volumetric flask. Dissolve in 20 mL of Solution B, dilute with Solution A to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 305-nm detector and a 4.6-mm × 5-cm column that contains 5-µm packing L1. The flow rate is about 3.0 mL per minute, and the column temperature is maintained at 35. The chromatograph is programmed as follows. [note—Adjust the start time of the gradient step and the equilibration time for each instrument.] Chromatograph the System suitability preparation, and record the peak responses as directed for Procedure: the relative retention times are about 1.0 for fluvastatin and 1.2 for fluvastatin anti-isomer; the resolution, R, between fluvastatin anti-isomer and fluvastatin is not less than 1.6; the column efficiency is not less than 700 theoretical plates for the fluvastatin peak; and the tailing factor is not more than 3.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 1.0%.

Procedure— 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 fluvastatin peaks. Calculate the quantity, in mg, of C24H25FNNaO4 in the portion of Fluvastatin Sodium taken by the formula: in which C is the concentration, in mg per mL, of USP Fluvastatin Sodium RS in the Standard preparation; and rU and rS are the fluvastatin peak responses obtained from the Assay preparation and the Standard preparation, respectively.