Related compounds
Phosphate buffer, Mobile phase, Standard stock solution, System suitability solution, and Chromatographic system
Proceed as directed in the Assay.
Standard solution
Dissolve accurately weighed quantities of
USP Clopidogrel Related Compound A RS,
USP Clopidogrel Related Compound B RS, and
USP Clopidogrel Related Compound C RS in methanol, and dilute with methanol to obtain a solution having concentrations of about 0.1, 0.4, and 0.3 mg per mL, respectively. Dilute this solution with
Mobile phase, and mix to obtain a solution having final concentrations of about 10, 40, and 30 µg per mL, respectively.
Test solution
Transfer about 100 mg of Clopidogrel Bisulfate, accurately weighed, to a 200-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix.
Procedure
Separately inject equal volumes (about 10 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the areas for all the peaks. Calculate the percentage of related compounds in the portion of Clopidogrel Bisulfate taken by the formula:
100(CS / CT)(rU / rS),
in which
CS is the concentration, in mg per mL, of relevant USP Clopidogrel Related Compound RS in the
Standard solution; CT is the concentration, in mg per mL, of Clopidogrel Bisulfate in the
Test solution; rU is the peak response for clopidogrel related compound obtained from the
Test solution; and
rS is the peak response for relevant clopidogrel related compound obtained from the
Standard solution: not more than 0.2% of clopidogrel related compound A is found; not more than 0.3% of clopidogrel related compound B is found; not more than 1.0% of clopidogrel related compound C is found; not more than 0.1% of any other impurity is found; and not more than 1.5% of total impurities is found.
Assay
Phosphate buffer
Dissolve 1.36 g of monobasic potassium phosphate in about 500 mL of water, and dilute with water to 1000 mL.
Mobile phase
Prepare a filtered and degassed mixture of
Phosphate buffer and acetonitrile (75:25). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard stock solution
Transfer about 100 mg of
USP Clopidogrel Bisulfate RS, accurately weighed, to a 100-mL volumetric flask. Dissolve in and dilute with methanol to volume, and mix.
Standard preparation
Dilute a suitable portion of Standard stock solution, accurately measured, with Mobile phase to obtain a solution having a known concentration of about 0.1 mg per mL.
System suitability solution
Dissolve an accurately weighed quantity of
USP Clopidogrel Related Compound B RS in methanol, and mix with a suitable portion of
Standard stock solution, to obtain concentrations of about 1.0 and 0.5 mg per mL, respectively. Dilute this solution with
Mobile phase, and mix to obtain a solution having a final concentration of about 0.05 mg per mL of clopidogrel bisulfate and about 0.1 mg per mL of clopidogrel related compound B.
Assay preparation
Transfer about 100 mg of Clopidogrel Bisulfate, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix. Pipet 5.0 mL of this solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.
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 packing L57 (see
Chromatography 621). 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 relative retention times are about 0.8 and 1.2 for enantiomers of clopidogrel related compound B, respectively, and 1.0 for clopidogrel; and the resolution,
R, between clopidogrel and the first enantiomer of clopidogrel related compound B is not less than 2.5. Chromatograph the
Standard preparation: the relative standard deviation for replicate injections determined from clopidogrel bisulfate is not more than 1.0%.
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 areas for all the peaks. Calculate the quantity, in mg, of C
16H
16ClNO
2S·H
2SO
4 in the portion of Clopidogrel taken by the formula:
1000C(rU / rS),
in which
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, respectively.