Identification—
A: Ultraviolet Absorption 
197U
—
Spectral range:
250 to 300 nm.
Solution—
Use the test solution prepared as directed in the test for Uniformity of dosage units.
B:
The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.
Dissolution 711—
Medium:
pH 2.0 hydrochloric acid buffer (see Buffer solutions under Reagents, Indicators, and Solutions); 1000 mL.
Apparatus 2:
50 rpm.
Time:
30 minutes.
Standard solution—
Dissolve an accurately weighed quantity of
USP Clopidogrel Bisulfate RS in 20.0 mL of methanol, and dilute quantitatively, and stepwise if necessary, with
Medium to obtain a solution having a known concentration corresponding to that of the solution under test.
Procedure—
Determine the amount of C16H16ClNO2S dissolved by employing UV absorption at the wavelength of maximum absorbance at about 240 nm on filtered portions of the solution under test in comparison with the Standard solution.
Tolerances—
Not less than 80% (Q) of the labeled amount of C16H16ClNO2S is dissolved in 30 minutes.
Related compounds—
Test solution—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 75 mg of clopidogrel, to a 200-mL volumetric flask, add 5 mL of methanol, dilute with Mobile phase to volume, and mix. Allow to stand for 10 minutes, and mix. Pass a portion of this solution through a filter having a 0.45-µm or finer porosity, and use the filtrate after discarding the first 5 mL.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 220-nm detector and 4.6-mm × 15-cm column that contains packing L57. The flow rate is about 1.0 mL per minute. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the resolution,
R, between clopidogrel and each of the two enantiomers of clopidogrel related compound B is not less than 2.5.
[NOTE—The relative retention times are about 0.5 for clopidogrel related compound A, 0.8 and 1.2 for the two enantiomers of clopidogrel related compound B, 1.0 for clopidogrel, and 2.0 for clopidogrel related compound C.
] Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 15%.
Procedure—
Inject equal volumes (about 10 µL) of the
Standard solution and
Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of related compounds in the portion of Tablets taken by the formula:
20(C/W)(rU / rS),
in which
C is the concentration, in µg per mL, of the appropriate USP Reference Standard in the
Standard solution; W is the weight, in mg, of clopidogrel in the portion of Tablets used to prepare the
Test solution based on the labeled quantity of clopidogrel per Tablet, Tablet weight, and the weight of the portion of Tablets used; and
rU and
rS are the peak responses of the corresponding related compounds obtained from the
Test solution and the
Standard solution, respectively: not more than 0.2% of clopidogrel related compound A is found, not more than 1.0% of clopidogrel related compound C is found, not more than 0.2% of any other single impurity (excluding clopidogrel related compound B) is found, and not more than 1.2% of total impurities (excluding clopidogrel related compound B) is found.
Assay—
Phosphate buffer, Mobile phase, Standard stock solution, Standard preparation, System suitability solution, and Chromatographic system—
Proceed as directed in the
Assay under
Clopidogrel Bisulfate.
Assay preparation—
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 100 mg of clopidogrel bisulfate, to a 100-mL volumetric flask, and add 50 mL of methanol. Sonicate for 5 minutes, and stir with a magnetic stirrer for 30 minutes. Dilute with methanol to volume, and mix. Transfer 5.0 mL of this solution to the flask, dilute with methanol to 50.0 mL, and mix. Pass a portion of this solution through a filter having a 0.45-µm or finer porosity, and use the filtrate after discarding the first 5 mL.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the analyte peaks. Calculate the quantity, in mg, of clopidogrel (C
16H
16ClNO
2S) in the portion of Tablets taken by the formula:
1000(321.82/419.90)C(rU / rS),
in which 321.82 is the molecular weight of clopidogrel; 419.90 is the molecular weight of clopidogrel bisulfate;
C is the concentration, in mg per mL, of
USP Clopidogrel Bisulfate RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respec-tively.
