Related compounds—
[NOTE—Use low-actinic glassware in this procedure.
]
Buffer solution—
Add 4.0 mL of n-butylamine to 1000 mL of water. Adjust with phosphoric acid to a pH of 3.00 ± 0.05.
Diluent—
Prepare a mixture of water, acetonitrile, and methanol (3:1:1).
Mobile phase—
Prepare a filtered and degassed mixture of
Buffer solution, acetonitrile, and methanol (3:1:1). Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
Standard stock solution —
Prepare a solution of
USP Glipizide RS in methanol containing about 0.1 mg per mL.
Test solution—
Transfer about 25 mg of Glipizide, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with methanol to volume, and mix. Pipet 4.0 mL of this solution into a 10-mL volumetric flask, dilute with Diluent to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 280-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The column temperature is maintained at 30
. The flow rate is about 1 mL per minute. Chromatograph the
Standard solution, and record the peak responses as directed for
Procedure: the retention time of the glipizide peak is about 45 minutes; the relative retention times for glipizide related compound A and glipizide are about 0.12 and 1.0, respectively; the relative retention time of another known impurity, methyl-
N-4-[2-(5-methylpyrazine-2-carboxamido)ethyl] benzenesulfonyl carbamate, is about 0.18; and the relative standard deviation for replicate injections is not more than 5.0% for each peak.
Procedure—
Separately inject equal volumes (about 35 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the peak responses. Calculate the percentage of glipizide related compound A in the portion of Glipizide taken by the formula:
6.25(CA / W)(rA / rSA),
in which
CA is the concentration, in µg per mL, of
USP Glipizide Related Compound A RS in the
Standard solution; W is the amount of Glipizide, in mg, taken to prepare the
Test solution; and
rA and
rSA are the peak responses for glipizide related compound A obtained from the
Test solution and the
Standard solution, respectively. Calculate the percentage of any other individual impurity in the portion of Glipizide taken by the formula:
6.25(CG / W)(ri / rSG),
in which
CG is the concentration, in µg per mL, of
USP Glipizide RS in the
Standard solution; ri is the peak response for each individual impurity obtained from the
Test solution; rSG is the glipizide peak response obtained from the
Standard solution; and
W is defined above. Disregard any impurity peak that is less than 0.05%. Not more than 0.5% of any individual impurity is found; and not more than 1.5% of total impurities is found.
Assay—
[NOTE—Use low-actinic glassware in this procedure.
]
Buffer—
Dissolve 13.8 g of monobasic sodium phosphate in water, and dilute with water to 1000 mL. Adjust with 2.0 N sodium hydroxide to a pH of 6.00 ± 0.05.
Mobile phase—
Prepare a filtered and degassed mixture of
Buffer and methanol (55:45). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Glipizide RS in methanol, and dilute quantitatively with methanol to obtain a solution having a known concentration of about 0.1 mg per mL. Transfer 25.0 mL of this solution to a 50-mL volumetric flask, dilute with
Buffer to volume, and mix to obtain a solution having a known concentration of about 0.05 mg per mL.
Assay preparation—
Transfer about 20 mg of glipizide, accurately weighed, to a 200-mL volumetric flask, and dissolve in and dilute with methanol to volume. Pipet 25 mL of this solution into a 50-mL volumetric flask, dilute with Buffer to volume, and mix to obtain a solution having a known concentration of about 0.05 mg per mL.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 225-nm detector and a 15-cm × 3.9-mm column that contains 5-µm packing L1. The flow rate is about 1.0 mL per minute. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 1.0%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of glipizide (C
21H
27N
5O
4S) in the portion of Glipizide taken by the formula:
400C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Glipizide RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
