A: Infrared Absorption 197K.

B: The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that of the Standard preparation, both relative to the internal standard, as obtained in the Assay.

Mobile phase— Prepare a filtered and degassed mixture of 0.5% trifluoroacetic acid, tetrahydrofuran, acetonitrile, and methanol (13.5:3:3:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard solution— Dissolve an accurately weighed quantity of USP Trazodone 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 2 µg per mL.

System suitability solution— Dissolve suitable quantities of 3-chloroaniline and USP Trazodone Hydrochloride RS in Mobile phase to obtain a solution containing about 0.1 mg per mL of 3-chloroaniline and 0.01 mg per mL of trazodone hydrochloride, respectively.

Test solution— Transfer about 50 mg of trazodone hydrochloride, accurately weighed, to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and filter.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 248-nm detector and a 4.6-mm × 15-cm column that contains 3-µm packing L7. The flow rate is about 1.0 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.6 for 3-chloroaniline and 1 for trazodone hydrochloride, and the resolution, R, between 3-chloroaniline and trazodone hydrochloride, is not less than 12. Chromatograph the Standard solution, and record the peak responses as directed for Procedure: the tailing factor for the analyte peak is not more than 2.0, and the relative standard deviation for replicate injections is not more than 5%.

Procedure— Separately inject equal volumes (about 10 µL) of the Standard solution and the Test solution into the chromatograph, record the chromatograms, and measure the responses for all of the peaks. Calculate the percentage of each peak, other than the trazodone hydrochloride peak, in the Trazodone Hydrochloride taken by the formula: in which CS is the concentration, in mg per mL, of USP Trazodone Hydrochloride RS in the Standard solution, CT is the concentration, in mg per mL, of trazodone hydrochloride in the Test solution, rU is the response of each peak, other than the trazodone hydrochloride peak, obtained from the Test solution, and rS is the peak response for trazodone hydrochloride obtained from the Standard solution: not more than 0.4% for any single impurity and not more than 1.0% of total impurities are found.

Test solution: methanol.

Standard solution: methanol.

Eluant: a mixture of cyclohexane, acetone, and ammonium hydroxide (8:4.5:0.5).

Visualization: 1.

(Official January 1, 2007)

0.01 M Ammonium phosphate buffer— Transfer 1.15 g of monobasic ammonium phosphate to a 1000-mL volumetric flask, and dissolve in water. Add 1.0 mL of 1 N sodium hydroxide, dilute with water to volume, and mix. Adjust this solution, if necessary, with either 10% phosphoric acid or 1 N sodium hydroxide to a pH of 6.0 ± 0.1, and filter.

Mobile phase— Prepare a filtered and degassed mixture of methanol and 0.01 M Ammonium phosphate buffer (60:40). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard solution— Dissolve a suitable quantity of butylparaben in methanol to obtain a solution containing about 2 mg per mL.

Standard preparation— Dissolve an accurately weighed quantity of USP Trazodone Hydrochloride RS in Mobile phase to obtain a solution having a known concentration of about 2.5 mg per mL. Transfer 4.0 mL of this solution to a 100-mL volumetric flask, add 2.0 mL of Internal standard solution, dilute with Mobile phase to volume, and mix to obtain a solution having a known concentration of about 0.1 mg of USP Trazodone Hydrochloride RS per mL.

Assay preparation— Transfer an accurately weighed quantity of about 125 mg of Trazodone Hydrochloride to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. Transfer 4.0 mL of this solution to a 100-mL volumetric flask, add 2.0 mL of the Internal standard solution, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 254-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the resolution, R, between the trazodone and butylparaben peaks is not less than 3.0, and the relative standard deviation for replicate injections 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 responses for the major peaks. The relative retention times are about 0.6 for butylparaben and 1.0 for trazodone. Calculate the quantity, in mg, of C19H22ClN5O·HCl in the portion of Trazodone Hydrochloride taken by the formula: in which C is the concentration, in mg per mL, of USP Trazodone Hydrochloride RS in the Standard preparation, and RU and RS are the ratios of the peak responses of the trazodone to the internal standard obtained from the Assay preparation and the Standard preparation, respectively.