Chromatographic purity—
Mobile phase, Standard preparation, and Chromatographic system—
Proceed as directed in the
Assay.
Test preparation—
Use the Assay preparation.
Procedure—
Inject a volume (about 15 µL) of the
Test preparation into the chromatograph, record the chromatogram, and measure the peak responses. Calculate the percentage of each impurity in the portion of Naftifine Hydrochloride taken by the formula:
100(ri / rS),
in which
ri is the peak response for each impurity, and
rS is the sum of the responses of all of the peaks: not more than 0.1% of any individual impurity is found, and the sum of all impurities is not more than 1.0%.
Assay—
Mobile phase—
Prepare a filtered and degassed mixture of
n-hexane, alcohol, dimethylformamide, and formic acid (200:60:40:2), cover tightly with a moisture-proof film, and allow to stand for 12 hours at room temperature. Make adjustments, if necessary (see
System Suitability under
Chromatography 
621
).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Naftifine Hydrochloride RS in
Mobile phase, and dilute quantitatively, and stepwise, if necessary, with
Mobile phase to obtain a solution having a known concentration of about 0.2 mg per mL.
Assay preparation—
Transfer about 10 mg of Naftifine Hydrochloride, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 270-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L3. The flow rate is about 2.0 mL per minute.
Procedure—
Separately inject equal volumes (about 15 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 C
21H
21N·HCl in the portion of Naftifine Hydrochloride taken by the formula:
50C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Naftifine Hydrochloride RS in the
Standard preparation, and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
for 4 hours: it loses not more than 0.5% of its weight.