Loss on drying (see Thermal Analysis á891ñ)
Determine the percentage of volatile substances by thermogravimetric analysis on an appropriately calibrated instrument,using about 30mg 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 200mLper 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 (3in 1000).Adjust with 1Nsodium hydroxide to a pHof 7.0.
Solution B
Use filtered and degassed methanol.
Mobile phase
Use variable mixtures of
Solution Aand
Solution Bas directed for
Chromatographic system.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Test solution
Transfer about 100mg of Repaglinide,accurately weighed,to a 10-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.
Standard solution
Transfer 0.1mLof the Test solutionto a 10-mLvolumetric flask,dilute with methanol to volume,and mix.
Chromatographic system (see Chromatography á621ñ)
Prepare as directed in the
Assay,except to program the chromatograph as follows.
Time (minutes) |
Solution A
(%) |
Solution B
(%) |
Elution |
| 0 |
50 |
50 |
equilibration |
| 02 |
50®30 |
50®70 |
linear gradient |
| 28 |
30 |
70 |
isocratic |
| 812 |
30®5 |
70®95 |
linear gradient |
| 1215 |
5 |
95 |
isocratic |
Chromatograph the
System suitability solution,and record the peak areas as directed for
Procedure:the relative retention times are about 0.3for repaglinide related compound B,0.9for repaglinide related compound C,1.0for repaglinide,and 1.6for 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 3µL)of the
Test solutionand the
Standard solutioninto 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
riis the peak response for each impurity obtained from the
Test solution;and
rSis 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 (1in 1000),and adjust with phosphoric acid to a pHof 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 RSin methanol,and dilute quantitatively,and stepwise if necessary,with methanol to obtain a solution having a known concentration of about 500µg per mL.
Assay preparation
Transfer about 25mg of Repaglinide,accurately weighed,to a 50-mLvolumetric flask,dissolve in and dilute with methanol to volume,and mix.
Chromatographic system(see Chromatography á621ñ)
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 1.0mLper 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 1.0for repaglinide and 0.4for 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 10µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the areas for the major peaks.Calculate the quantity,in mg,of C
27H
36N
2O
4in the portion of Repaglinide taken by the formula:
50C(rU/rS),
in which
Cis the concentration,in mg per mL,of
USP Repaglinide RSin the
Standard preparation;and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.