A: Infrared Absorption á197Kñ.

B: Ultraviolet Absorption á197Uñ—

C: To 10mLof a solution (1in 400)add 2drops of nitric acid and 1mLof silver nitrate TS:a curdy,white precipitate,insoluble in 2Nnitric acid,but soluble in 6Nammonium hydroxide,separates (presence of chloride).

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and 0.12Nsulfuric acid (90:10).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Standard preparation— Dissolve an accurately weighed quantity of USP Hydroxyzine Hydrochloride RSquantitatively in Mobile phaseto obtain a solution having a known concentration of about 1.8µg per mL.

Resolution solution— Dissolve suitable quantities of USP Hydroxyzine Hydrochloride RSand USPp-Chlorobenzhydrylpiperazine RSin Mobile phaseto obtain a solution containing 3.6µg 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 phaseto volume to obtain a solution containing a known concentration of about 0.6mg of specimen per mL,and mix.

Chromatographic system (see Chromatography á621ñ)—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 0.4mLper minute.Chromatograph the Resolution solutionand 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 preparationis not more than 2.0%.

Procedure— Separately inject equal volumes (about 20µL)of the Standard preparationand the Test preparationinto the chromatograph,record the chromatograms for a total time of not less than 1.8times 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: in which CSis the concentration,in µg per mL,of USP Hydroxyzine Hydrochloride RSin the Standard preparation;CUis the concentration,in mg per mL,of specimen in the Test preparation;rUis the peak response of a given impurity in the chromatogram obtained from the Test preparation;and rSis 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%.