Chromatographic purity—
Mobile phase—
Prepare a filtered and degassed mixture of acetonitrile and 0.12 N sulfuric acid (90:10). Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Hydroxyzine Hydrochloride RS quantitatively in
Mobile phase to obtain a solution having a known concentration of about 1.8 µg per mL.
Resolution solution—
Dissolve suitable quantities of
USP Hydroxyzine Hydrochloride RS and USP
p-Chlorobenzhydrylpiperazine RS in
Mobile phase to obtain a solution containing 3.6 µg of each per mL.
Test preparation—
Transfer an accurately weighed quantity of Hydroxyzine Hydrochloride to a suitable volumetric flask, dissolve in and dilute with Mobile phase to volume to obtain a solution containing a known concentration of about 0.6 mg of specimen per mL, and mix.
Chromatographic system
(see
Chromatography 621)—The liquid chromatograph is equipped with a 230-nm detector, and two series-coupled 3-mm × 10-cm columns that contain packing L3. The flow rate is about 0.4 mL per minute. Chromatograph the
Resolution solution and the
Standard preparation, and record the peak responses as directed under
Procedure: the resolution,
R, between the
p-chlorobenzhydrylpiperazine and hydroxyzine peaks is not less than 1.2, and the relative standard deviation for replicate injections of the
Standard preparation is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Standard preparation and the
Test preparation into the chromatograph, record the chromatograms for a total time of not less than 1.8 times the retention time of the hydroxyzine peak, and measure the response for each peak, except for the main hydroxyzine peak in the chromatogram obtained from the
Test preparation. Calculate the apparent percentage of each impurity in the specimen taken by the formula:
0.1(CS / CU)(rU / rS),
in which
CS is the concentration, in µg per mL, of
USP Hydroxyzine Hydrochloride RS in the
Standard preparation;
CU is the concentration, in mg per mL, of specimen in the
Test preparation;
rU is the peak response of a given impurity in the chromatogram obtained from the
Test preparation; and
rS is the peak response of hydroxyzine in the chromatogram obtained from the
Standard preparation: not more than 0.3% of any impurity is found, and the sum of all impurities found is not greater than 1.5%.
Assay—
Dissolve about 80 mg of Hydroxyzine Hydrochloride, accurately weighed, in 50 mL of a mixture of acetic anhydride and glacial acetic acid (7:3), and titrate with 0.1 N perchloric acid VS, determining the endpoint potentiometrically, using a glass electrode and a silver-silver chloride electrode containing saturated lithium perchlorate and saturated silver chloride in glacial acetic acid (see
Titrimetry 541). Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 22.39 mg of C
21H
27ClN
2O
2·2HCl.
;)
-phenylbenzyl)-1-piperazinyl]ethoxy]ethanol dihydrochloride
for 3 hours: it loses not more than 5.0% of its weight.