pH 
791
:
between 4.8 and 6.5. To prepare the test solution, dissolve 5.6 g of Diluted Isosorbide Mononitrate in 50 mL of boiling water, sonicate for 5 minutes, and allow to cool to room temperature.
Water, Method Ic 921:
between 0.4% and 0.8%. Proceed as directed for hygroscopic materials. To 1.0 g of sample, accurately weighed, add 5 mL of methanol, shake for 30 minutes, and centrifuge at about 2500 rpm for 5 minutes. Use 1.0 mL of the resulting supernatant.
Related compounds—
TEST 1—
Adsorbent:
0.25-mm layer of chromatographic silica gel mixture.
Standard solution 1—
Weigh accurately a quantity of
USP Isosorbide RS, and dilute quantitatively, and stepwise if necessary, with absolute alcohol to obtain a solution having a known concentration of about 0.0125 mg of isosorbide per mL.
Standard solution 2—
Weigh accurately a quantity of
USP Isosorbide RS, and dilute quantitatively, and stepwise if necessary, with absolute alcohol to obtain a solution having a known concentration of about 0.025 mg of isosorbide per mL.
Standard solution 3—
Weigh accurately a quantity of
USP Isosorbide RS, and dilute quantitatively, and stepwise if necessary, with absolute alcohol to obtain a solution having a known concentration of about 0.05 mg of isosorbide per mL.
Test solution—
Transfer a portion of Diluted Isosorbide Mononitrate, equivalent to about 200 mg of isosorbide mononitrate, accurately weighed, to a suitable container, add 20.0 mL of absolute alcohol, sonicate for 10 minutes, and then centrifuge. Use the supernatant.
Application volume:
20 µL.
Developing solvent system:
a mixture of absolute alcohol and toluene (8:2).
Procedure—
Proceed as directed for
Thin-Layer Chromatography under
Chromatography 621. After developing, dry the plate with warm air for about 10 minutes, dip the plate in a solution prepared by dissolving 1.25 g of potassium permanganate and 10.0 g of sodium hydroxide in 500 mL of water (prepared fresh for each plate), and heat at 105
for 5 minutes. Any spot in the chromatogram obtained from the
Test solution and corresponding to the
RF value of the spots obtained from the
Standard solutions is not more intense than the spot in the chromatogram obtained from
Standard solution 3: not more than 0.5% of any individual impurity is found. If the spot in the chromatogram obtained from the
Test solution is nearly as intense as the spot obtained from
Standard solution 3, further dilute the
Test solution (1:1) with absolute alcohol, repeat the test, and compare the intensity of the isosorbide spot in the diluted
Test solution with the intensity of the spots obtained from the
Standard solutions, correcting the percent level for the additional dilution of the
Test solution.
TEST 2—
Mobile phase, Resolution solution, and Chromatographic system—
Proceed as directed in the Assay.
Isosorbide mononitrate related compound A standard solution—
Prepare as directed for Isosorbide mononitrate related compound A standard preparation in the Assay.
Isosorbide dinitrate standard stock solution—
Dissolve an accurately weighed quantity of
USP Diluted Isosorbide Dinitrate RS in methanol, sonicate and warm if necessary, and dilute quantitatively, and stepwise if necessary, with methanol to obtain a solution having a known concentration of about 0.125 mg of isosorbide dinitrate per mL.
Standard solution—
Transfer a quantity of
USP Isosorbide Mononitrate RS, accurately weighed, to a suitable volumetric flask. Dissolve in water, quantitatively add a volume of
Isosorbide mononitrate related compound A standard solution and a volume of
Isosorbide dinitrate standard stock solution, and dilute with water to volume to obtain a solution having a known concentration of about 2.0 mg of
USP Isosorbide Mononitrate RS per mL, 0.005 mg of isosorbide mononitrate related compound A per mL, and 0.005 mg of isosorbide dinitrate per mL. Filter a portion of the solution, discarding the first few mL of the filtrate.
Test solution—
Use the Assay preparation, prepared as directed in the Assay.
Procedure—
Separately inject equal volumes (about 50 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the percentage of isosorbide mononitrate related compound A and isosorbide dinitrate relative to the amount of isosorbide mononitrate in the portion of Diluted Isosorbide Mononitrate taken by the formula:
5556(C/W)(rU / rS),
in which
C is the concentration, in mg per mL, of the appropriate Reference Standard,
USP Isosorbide Mononitrate Related Compound A RS or
USP Diluted Isosorbide Dinitrate RS, in the
Standard solution; W is the weight, in mg, of Diluted Isosorbide Mononitrate used to prepare the
Test solution; and
rU and
rS are the peak areas of the corresponding components obtained from the
Test solution and the
Standard solution, respectively: not more than 0.25% of isosorbide mononitrate related compound A is found; and not more than 0.25% of isosorbide dinitrate is found. Calculate the percentage of each other impurity (other than isosorbide mononitrate related compound A or isosorbide dinitrate) in the portion of Diluted Isosorbide Mononitrate taken by the formula:
100(ri / rs),
in which
ri is the peak area for each other impurity obtained from the
Test solution; and
rs is the sum of the areas of all the peaks: not more than 0.5% of total impurities is found including isosorbide mononitrate related compound A and isosorbide dinitrate; and not more than 0.5% of total impurities is found, the results for
Test 1 and
Test 2 being considered.
Assay—
Mobile phase—
Prepare a filtered and degassed mixture of water and methanol (95:5). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Transfer an accurately weighed quantity of
USP Isosorbide Mononitrate RS to a suitable volumetric flask, dissolve in water, add a volume of methanol equivalent to 4% of the flask volume, and dilute with water to volume to obtain a solution having a known concentration of about 2.0 mg per mL.
Isosorbide mononitrate related compound A standard preparation—
Dissolve an accurately weighed quantity of
USP Isosorbide Mononitrate Related Compound A RS in methanol, and dilute quantitatively, and stepwise if necessary, with methanol to obtain a solution having a known concentration of about 1.0 mg per mL. Quantitatively dilute a portion of this solution with water to obtain a solution having a known concentration of about 0.05 mg per mL.
Resolution solution—
Transfer 10.0 mL of Isosorbide mononitrate related compound A standard preparation, 1.0 mL of Standard preparation, and 4.0 mL of methanol to a 100-mL volumetric flask, and dilute with water to volume. Filter a portion of the solution, discarding the first few mL of the filtrate.
Assay preparation—
Transfer about 110 mg of Diluted Isosorbide Mononitrate, accurately weighed, to a 50-mL volumetric flask, dissolve in about 25 mL of water, add 2 mL of methanol, dilute with water to volume, and mix. Filter a portion of the solution, discarding the first few mL of the filtrate.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 220-nm detector and a 4-mm × 12.5-cm column that contains packing L1. The flow rate is about 1.5 mL per minute, increasing to 3.0 mL per minute at about 8.5 minutes to ensure that the isosorbide mononitrate peak has completely eluted. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.8 for isosorbide mononitrate related compound A, 1.0 for isosorbide mononitrate, and 4.1 for isosorbide dinitrate; and the resolution,
R, between isosorbide mononitrate related compound A and isosorbide mononitrate is not less than 2.0. 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—
Separately inject equal volumes (about 50 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the isosorbide mononitrate peaks. Calculate the quantity, in mg, of isosorbide mononitrate (C
6H
9NO
6) in the portion of Diluted Isosorbide Mononitrate taken by the formula:
50C(rU / rS),
in which
C is the concentration, in mg per mL, of isosorbide mononitrate in the
Standard preparation; and
rU and
rS are the peak areas obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
