Related compounds—
TEST 1—
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture.
Test solution—
Dissolve an accurately weighed quantity of Metoprolol Succinate in methanol to obtain a solution containing 50 mg per mL.
Standard solution—
Dilute the Test solution quantitatively, and stepwise if necessary, with methanol to obtain a solution having a concentration of 0.1 mg per mL.
Application volume:
10 µL.
Developing solvent system:
a mixture of ethyl acetate and methanol (80:20).
Procedure—
Proceed as directed for
Thin-Layer Chromatography under
Chromatography 
621
. Place two 50-mL beakers, each containing 30 mL of ammonium hydroxide, on the bottom of a chromatographic chamber that is lined with filter paper and contains the
Developing solvent system, and allow to equilibrate for l hour. Position the plate in the chromatographic chamber, and develop the chromatogram until the solvent front has moved about two-thirds of the length of the plate. Remove the plate from the chamber, mark the solvent front, and dry the plate for 3 hours in a current of warm air. Place the plate in a chamber containing iodine vapor, and allow to react for at least 15 hours. Compare the intensities of the brown spots appearing on the chromatogram: any secondary spot obtained from the
Test solution is not more intense than the corresponding spot obtained from the
Standard solution. Not more than 0.2% is found.
TEST 2—
Sodium dodecyl sulfate solution, Mobile phase, and Resolution solution—
Prepare as directed in the Assay.
Standard solution—
Dissolve an accurately weighed quantity of
USP Metoprolol Succinate RS in
Mobile phase, and dilute quantitatively, and stepwise if necessary, with
Mobile phase to obtain a solution having a known concentration of about 1.0 µg per mL.
Test solution—
Transfer about 50 mg of Metoprolol Succinate, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
Prepare as directed in the
Assay. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the resolution,
R, between metoprolol related compound A and metoprolol related compound B is not less than 1.5; and the resolution,
R, between metoprolol related compound B and metoprolol related compound C is not less than 2.5.
[NOTE—The relative retention times are about 0.6 for metoprolol related compound C, 0.7 for metoprolol related compound B, 0.8 for metoprolol related compound A, 1.0 for metoprolol, and 5.0 and 5.2 for the two diastereomers of metoprolol related compound D.
] Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 5.0%.
Procedure—
Inject equal volumes (about 10 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of each impurity in the portion of Metoprolol Succinate taken by the formula:
100(CS / CT)(ri / rS),
in which
CS is the concentration, in mg per mL, of
USP Metoprolol Succinate RS in the
Standard solution; CT is the concentration of metoprolol succinate in the
Test solution; ri is the individual peak response of related impurities; and
rS is the peak response obtained from the
Standard solution: not more than 0.1% of any single impurity is found, and not more than 0.5% of total impurities is found.
[NOTE—The sum of the peak responses for the two diastereomers of metoprolol related compound D is used in the above calculation to report the amount of metoprolol related compound D.
]
Assay—
Sodium dodecyl sulfate solution—
Add 1.3 g of sodium dodecyl sulfate to 1 L of aqueous phosphoric acid, 0.1% (w/v).
Mobile phase—
Prepare a filtered and degassed mixture of
Sodium dodecyl sulfate solution and acetonitrile (60:40). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Metoprolol Succinate RS in
Mobile phase, and dilute quantitatively, and stepwise if necessary, with
Mobile phase to obtain a solution having a known concentration of about 0.08 mg per mL.
Test preparation—
Transfer about 80 mg of Metoprolol Succinate, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. Transfer 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 223-nm detector and a 4-mm × 12.5-cm column that contains 4-µm packing L7. The column temperature is maintained at 30
. The flow rate is about 0.9 mL per minute. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the resolution,
R, between metoprolol related compound A and metoprolol related compound B is not less than 1.5; and the resolution,
R, between metoprolol related compound B and metoprolol related compound C is not less than 2.5.
[NOTE—The relative retention times are about 0.6 for metoprolol related compound C, 0.7 for metoprolol related compound B, 0.8 for metoprolol related compound A, 1.0 for metoprolol, and 5.0 and 5.2 for the two diastereomers of metoprolol related compound D.
] Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Inject equal volumes (about 10 µL) of the
Standard preparation and the
Test preparation into the chromatograph, record the chromatograms for at least 1.5 times the retention of the metoprolol peak, and measure the peak responses. Calculate the quantity, in mg, of (C
15H
25NO
3)
2·C
4H
6O
4 in the portion of Metoprolol Succinate taken by the formula:
1000C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Metoprolol Succinate RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Test preparation and the
Standard preparation, respectively.
;)
