Limit of residual solvents—
Internal standard solution—
Prepare a solution of isobutyl alcohol in dimethylformamide containing 2 µL of isobutyl alcohol per 100 mL of solution.
Standard solution—
Prepare a solution in Internal standard solution containing 5 µL each of acetone, alcohol, chloroform, diisopropyl ether, and methanol per 100 mL of solution.
System suitability solution—
Dilute a portion of the Standard solution with Internal standard solution to obtain a solution containing 0.05 µL each of acetone, alcohol, chloroform, diisopropyl ether, and methanol per 100 mL of solution.
Test solution—
Transfer about 40 mg of Norgestimate and 2 mL of Internal standard solution to a 5-mL volumetric flask or a suitable vial, and shake well to dissolve.
Chromatographic system (see Chromatography 
621
)—
The gas chromatograph is equipped with a flame-ionization detector, a 0.53-mm × 30-m fused-silica capillary column bonded with a 1-µm layer of phase G16, and a split injection system. The detector temperature is about 250
, and the injection port temperature is about 180
. The column temperature is programmed as follows. It is maintained at about 65
for 2.5 minutes, increased at a rate of 35
per minute to 100
, maintained for 2 minutes, then at a rate of 30
per minute increased to 160
, and maintained for 2.5 minutes. The carrier gas is helium, flowing at a rate of about 6 mL per minute, and the split flow rate is about 16 mL per minute. Chromatograph the
Internal standard solution, the
Standard solution, and the
System suitability solution, and record the peak responses as directed for
Procedure: there are no interfering peaks due to dimethylformamide; the retention time of isobutyl alcohol in the chromatogram of the
Internal standard solution is between 4 and 5 minutes; the signal-to-noise ratio for alcohol obtained from the
System suitability solution is not less than 2.0; and the relative standard deviation for replicate injections of the
Standard solution, determined from the peak response ratios of each solvent to the internal standard, is not more than 3.0%.
Procedure—
Separately inject equal volumes (about 1 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the responses for the major peaks. Calculate the percentage of each solvent in the portion of Norgestimate taken by the formula:
200(CD/W)(RU / RS),
in which
C is the concentration, in mL per mL, of each solvent in the
Standard solution; D is the density, in mg per mL, of each solvent;
W is the weight, in mg, of Norgestimate taken to prepare the
Test solution; and
RU and
RS are the peak response ratios of the appropriate analyte to the internal standard obtained from the
Test solution and the
Standard solution, respectively. Not more than 0.5% each of acetone and alcohol is found; not more than 0.05% of diisopropyl ether is found; not more than 0.006% of chloroform is found; and not more than 0.3% of methanol is found.
Chromatographic purity—
TEST 1—
Diluent, Mobile phase, System suitability solution, and Chromatographic system—
Proceed as directed in the Assay.
Standard solution—
Use the Standard preparation, prepared as directed in the Assay.
Test solution—
Use the Assay preparation, prepared as directed in the Assay.
Procedure—
Separately inject equal volumes (about 25 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the percentage of each impurity in the portion of Norgestimate taken by the formula:
5000(CP/W)(ri /FrS),
in which
C is the concentration, in mg per mL, of
USP Norgestimate RS in the
Standard solution; P is the fraction of (
E)-norgestimate in
USP Norgestimate RS;
W is the weight, in mg, of Norgestimate taken to prepare the
Test solution; ri is the peak area for each impurity obtained from the
Test solution; F is the relative response factor and it is equal to 0.83 for any peak having a relative retention time of 0.50, 1.13 for any peak having a relative retention time of 0.56, 0.85 for any peak having a relative retention time of 0.72, and 1.0 for any other peak; and
rS is the peak area of
(E)-norgestimate obtained from the
Standard solution. Not more than 0.3% of total impurities having relative retention times of 0.50 and 0.56 is found; not more than 0.3% of the impurity having a relative retention time of 0.72 is found; and not more than 0.1% of any other impurity is found.
TEST 2—
Mobile phase—
Prepare a filtered and degassed mixture of cyclohexane and absolute alcohol (50:1). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard solution—
Dissolve an accurately weighed quantity of
USP Norgestimate 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 mg per mL.
System suitability solution—
Dilute a portion of the Standard solution, quantitatively and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 0.5 µg per mL.
Test solution—
Transfer about 10 mg of Norgestimate, accurately weighed, to a 10-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 210-nm detector and a 4.6-mm × 25-cm column that contains a 5-µm packing L20. The flow rate is about 1 mL per minute. Chromatograph the
System suitability solution, and record the peak responses as directed for
Procedure: the signal-to-noise ratio for
(E)-norgestimate is not less than 3.0. Chromatograph the
Standard solution, and record the peak areas as directed for
Procedure: the retention time is about 18.6 minutes for
(E)-norgestimate; the relative retention times are about 1.0 for
(E)-norgestimate and 1.1 for
(Z)-norgestimate; the tailing factor is not more than 1.5; the resolution,
R, between
(Z)-norgestimate and
(E)-norgestimate is not less than 1.5; and the relative standard deviation for replicate injections, determined from the peak area of
(Z)-norgestimate to
(E)-norgestimate, is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 25 µL) of the
Standard solution and the
Test solution into the chromatograph, record the chromatograms, and measure the peak areas. Calculate the percentage of each impurity in the portion of Norgestimate taken by the formula:
1000(CP/W)(ri / FrS),
in which
C is the concentration, in mg per mL, of
USP Norgestimate RS in the
Standard solution; P is the fraction of
(E)-norgestimate in
USP Norgestimate RS;
W is the weight, in mg, of Norgestimate taken to prepare the
Test solution; ri is the peak area for each impurity obtained from the
Test solution; F is the relative response factor and it is equal to 1.4 for any peak having a relative retention time of 0.74, 1.5 for any peak having a relative retention time of 0.78, and 1.2 for any peak having a relative retention time of 0.91; and
rS is the peak area of
(E)-norgestimate obtained from the
Standard solution. Not more than 0.2% of the impurity having a relative retention time of 0.74 is found; and not more than 0.1% each of the impurities having relative retention times of 0.78 and 0.91. Not more than 1.0% of total impurities is found, the results for
Test 1 and
Test 2 being added.
Assay—
Diluent—
Prepare a mixture of water and methanol (1:4).
Mobile phase—
Prepare a filtered and degassed mixture of water, tetrahydrofuran, and acetonitrile (30:11:9). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Norgestimate RS in
Diluent, and dilute quantitatively, and stepwise if necessary, with
Diluent to obtain a solution having a known concentration of about 0.5 mg per mL.
System suitability solution—
Dilute a portion of Standard preparation, quantitatively and stepwise if necessary, with Diluent to obtain a solution having a known concentration of about 0.05 µg per mL.
Assay preparation—
Transfer about 25 mg of Norgestimate, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Diluent to volume, and mix.
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 244-nm detector and a 4.6-mm × 10-cm column that contains a 3-µm packing L1. The flow rate is about 1.2 mL per minute. The column temperature is maintained at about 40
. Chromatograph the
System suitability solution, and record the peak areas as directed for
Procedure: the signal-to-noise ratio for
(Z)-norgestimate is not less than 3.0. Chromatograph the
Standard preparation, and record the peak areas as directed for
Procedure: the relative retention times are about 0.86 for
(Z)-norgestimate and 1.0 for
(E)-norgestimate; the resolution,
R, between
(Z)-norgestimate and
(E)-norgestimate is not less than 1.5; the tailing factor for
(E)-norgestimate and for
(Z)-norgestimate is not more than 1.5; and the relative standard deviation for replicate injections, determined from the peak area ratio of
(E)-norgestimate to
(Z)-norgestimate, is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 25 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
23H
31NO
3 in the portion of Norgestimate taken by the formula:
50C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Norgestimate RS in the
Standard preparation; and
rU and
rS are the sums of peak areas of
(Z)-norgestimate and
(E)-norgestimate obtained from the
Assay preparation and the
Standard preparation, respectively. Calculate the percentages of the
(Z)- and
(E)-isomers,
UZ and
UE, respectively, in the portion of Norgestimate taken by the formula:
5000(CP/W)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Norgestimate RS in the
Standard preparation; P is the fraction of
(E)- or
(Z)-norgestimate in
USP Norgestimate RS;
W is the weight, in mg, of Norgestimate taken to prepare the
Assay preparation; and
rU and
rS are the peak responses of the appropriate norgestimate isomer obtained from the
Assay preparation and the
Standard preparation, respectively. Calculate the ratio of
(E)-norgestimate to
(Z)-norgestimate, that is, the ratio of
UE to
UZ.
;)
)-(+)-.