Assay—
pH 7.4 Buffer
,
Mobile phase, and
Chromatographic system—Prepare as directed in the
Assay under
Warfarin Sodium.
Internal standard solution—
Dissolve propylparaben in a solvent consisting of a mixture of acetonitrile and glacial acetic acid (988:12) to obtain a solution having a concentration of about 1.0 mg per mL.
Standard preparation—
Transfer about 94 mg of
USP Warfarin RS, accurately weighed, to a 100-mL volumetric flask, and dissolve in 39.1 mL of 0.1 N sodium hydroxide. Add 25.0 mL of 0.2
M monobasic potassium phosphate, dilute with water to volume, and mix. Pipet 5 mL of this solution and 5 mL of
Internal standard solution into a 50-mL volumetric flask, dilute with
pH 7.4 Buffer to volume, and mix.
Assay preparation—
Dissolve the contents of not fewer than 10 containers of Warfarin Sodium for Injection in a sufficient volume, accurately measured, of pH 7.4 buffer to obtain a solution containing about 1 mg of warfarin sodium per mL. Pipet 5 mL of the resulting solution and 5 mL of Internal standard solution into a 50-mL volumetric flask, dilute with pH 7.4 buffer to volume, and mix.
Procedure—
Proceed as directed for
Procedure in the
Assay under
Warfarin Sodium. Calculate the average quantity, in mg, of warfarin sodium (C
19H
15NaO
4) in each container of Warfarin Sodium for Injection taken by the formula:
10(330.32 / 308.34)(VC / N)(RU / RS),
in which 330.32 and 308.34 are the molecular weights of warfarin sodium and warfarin, respectively;
V is the volume, in mL, of the solution prepared from the contents of the 10 or more containers;
C is the concentration, in mg per mL, of
USP Warfarin RS in the
Standard preparation; N is the number of containers taken; and
RU and
RS are the peak response ratios of warfarin to propylparaben obtained from the
Assay preparation and the
Standard preparation, respectively.
1
.