Loss on drying (see Thermal Analysis 
891
)—
Determine the percentage of volatile substances by thermogravimetric analysis on an appropriately calibrated instrument, using about 30 mg of Repaglinide, accurately weighed. Heat the specimen at the rate of 10
per minute between 30
and 210
in an atmosphere of nitrogen at a flow rate of 200 mL per minute. From the thermogram, determine the accumulated loss in weight between 30
and 200
: it loses not more than 0.7% of its weight.
Chromatographic purity—
Solution A—
Prepare a filtered and degassed monobasic potassium phosphate solution (3 in 1000). Adjust with 1 N sodium hydroxide to a pH of 7.0.
Solution B—
Use filtered and degassed methanol.
Mobile phase—
Use variable mixtures of
Solution A and
Solution B as directed for
Chromatographic system. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Test solution—
Transfer about 100 mg of Repaglinide, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix.
Standard solution—
Transfer 0.1 mL of the Test solution to a 10-mL volumetric flask, dilute with methanol to volume, and mix.
Chromatographic system (see Chromatography 621)—
Prepare as directed in the
Assay, except to program the chromatograph as follows.
Time
(minutes) |
Solution A
(%) |
Solution B
(%) |
Elution |
| 0 |
50 |
50 |
equilibration |
| 0–2 |
50®30 |
50®70 |
linear gradient |
| 2–8 |
30 |
70 |
isocratic |
| 8–12 |
30®5 |
70®95 |
linear gradient |
| 12–15 |
5 |
95 |
isocratic |
Chromatograph the
System suitability solution, and record the peak areas as directed for
Procedure: the relative retention times are about 0.3 for repaglinide related compound B, 0.9 for repaglinide related compound C, 1.0 for repaglinide, and 1.6 for repaglinide related compound A. Chromatograph the
Standard solution, and record the peak areas as directed for
Procedure: the relative standard deviation for replicate injections is not more than 10%.
Procedure—
Separately inject equal volumes (about 3 µL) of the
Test solution and the
Standard solution into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the percentage of each impurity, other than repaglinide related compound A, in the portion of Repaglinide taken by the formula:
ri / rS,
in which
ri is the peak response for each impurity obtained from the
Test solution; and
rS is the peak response of repaglinide obtained from the
Standard solution. For repaglinide related compound A, use the same formula, but multiply the result by a response factor equal to 2.0: not more than 0.1% of any individual impurity is found, and not more than 0.5% of total impurities is found.
Assay—
Buffer solution—
Prepare a monobasic potassium phosphate solution (1 in 1000), and adjust with phosphoric acid to a pH of 2.5.
Mobile phase—
Prepare a filtered and degassed mixture of methanol and Buffer solution (80:20).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Repaglinide RS in methanol, and dilute quantitatively, and stepwise if necessary, with methanol to obtain a solution having a known concentration of about 500 µg per mL.
Assay preparation—
Transfer about 25 mg of Repaglinide, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 240-nm detector and a 4.6-mm × 12.5-cm column that contains 5-µm packing L1. The flow rate is about 1.0 mL per minute. The column temperature is maintained at 45
. Chromatograph the
System suitability preparation, and record the peak areas as directed for
Procedure: the relative retention times are about 1.0 for repaglinide and 0.4 for repaglinide related compound B. Chromatograph the
Standard preparation, and record the peak areas as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
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 the major peaks. Calculate the quantity, in mg, of C
27H
36N
2O
4 in the portion of Repaglinide taken by the formula:
50C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Repaglinide RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
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