A: Thin-Layer Chromatographic Identification Test 201—

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

Mobile phase— Prepare a mixture of 15 mmol of sodium dodecyl sulfate in a mixture of water and acetonitrile (1:1). Adjust with phosphoric acid to a pH of 2.6 ± 0.1, filter, and degas. Make adjustments if necessary (see System Suitability under Chromatography 621).

Diluent— Prepare a mixture of Mobile phase and water (2:1).

System suitability solution 1— Dissolve an accurately weighed quantity of USP Loratadine RS, and dilute quantitatively, and stepwise if necessary, to obtain a solution having a known concentration of about 0.002 mg per mL.

System suitability solution 2— Quantitatively transfer 5.0 mL of System suitability solution 1 into a suitable container, dilute with Diluent to 50 mL, and mix.

Resolution solution— Transfer an amount of Oral Solution, equivalent to 20 mg of loratadine, into a screw-cap glass container. Add 1 mL of 3% aqueous hydrogen peroxide, and mix. Cap, and heat at 65 for 18 to 24 hours. Allow to cool to room temperature, then dilute 5 mL with Diluent to 25 mL.

Test solution— Transfer an accurately measured volume of Oral Solution, equivalent to about 5 mg of loratadine, to a 25-mL volumetric flask, dilute with Diluent to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm × 25-cm column that contains 5-µm packing L7. The flow rate is about 2 mL per minute. The column temperature is maintained between 30 and 40. Chromatograph the Resolution solution, and record the peak areas as directed for Procedure: the relative retention times are about 0.70 for ethyl 4-[8-chloro-5,6-dihydro-4-(hydroxymethyl)-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene]-1-piperidinecarboxylate, 0.84 for ethyl 4-[8-chloro-5,6-dihydro-2-(hydroxymethyl)-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene]-1-piperidinecarboxylate, and 1.0 for loratadine; and the resolution, R, between loratadine and ethyl 4-[8-chloro-5,6-dihydro-2-(hydroxymethyl)-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene]-1-piperidinecarboxylate is not less than 3.0. Chromatograph System suitability solution 1, and record the peak area response of the loratadine peak as directed for Procedure: the tailing factor is not less than 0.7 and not greater than 1.1. Chromatograph System suitability solution 2, and record the peak area response of the loratadine peak as directed for Procedure: the relative standard deviation for replicate injections of System suitability solution 2 is not more than 10%.

Procedure— Inject about 50 µL of the Test solution into the chromatograph, record the chromatogram, and measure all the peak area responses. Calculate the percentage of each individual related compound in the portion of Oral Solution taken by the formula: in which ri is the individual peak response of each related compound in the Test solution; and rs is sum of the responses of all the peaks, excluding excipient peaks: not more than 0.3% of ethyl 4-[8-chloro-5,6-dihydro-4-(hydroxymethyl)-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene]-1-piperidinecarboxylate is found; not more than 0.3% of ethyl 4-[8-chloro-5,6-dihydro-2-(hydroxymethyl)-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidene]-1-piperidinecarboxylate is found; not more than 0.2% of any other individual impurity is found; and the sum of all impurities is not more than 0.5%.

0.05 M Monobasic potassium phosphate solution— Transfer about 6.8 g of monobasic potassium phosphate, accurately weighed, to a 1-L volumetric flask, dissolve in and dilute with water to volume, and mix. Adjust with phosphoric acid to a pH of 3.0 ± 0.1.

Mobile phase— Prepare a filtered and degassed mixture of 0.05 M Monobasic potassium phosphate solution and acetonitrile (7:3). Make adjustments if necessary (see System Suitability under Chromatography 621).

Internal standard preparation— Dissolve an accurately weighed quantity of butylparaben in a mixture of water and acetonitrile (7:3), and dilute quantitatively, and stepwise if necessary, with a mixture of water and acetonitrile (7:3) to obtain a solution having a concentration of about 0.3 mg per mL.

Standard stock preparation— Dissolve an accurately weighed quantity of USP Loratadine RS in acetonitrile, and dilute quantitatively, and stepwise if necessary, with acetonitrile to obtain a solution having a known concentration of about 1.0 mg per mL.

Standard preparation— Transfer 5.0 mL of Internal standard preparation, 5.0 mL of Standard stock preparation, and 12 mL of water into a 50-mL volumetric flask. Dilute with a mixture of water and acetonitrile (7:3), and mix.

Assay preparation— Transfer an accurately measured quantity of Oral Solution, equivalent to 5 mg of loratadine, into a 50-mL volumetric flask. Pipet 5.0 mL of Internal standard preparation into the flask, dilute with a mixture of water and acetonitrile (7:3) to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 254-nm detector and a 4-mm × 30-cm column that contains 10-µm packing L11. The flow rate is about 2 mL per minute. The column temperature is maintained between 20 and 30. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative retention times are about 0.78 for butylparaben and 1.0 for loratadine; the resolution, R, between loratadine and butylparaben is not less than 1.9; the tailing factor is not more than 1.6 for the loratadine and butylparaben peaks; and the relative standard deviation for replicate injections is not more than 2%.

Procedure— Separately inject equal volumes (about 10 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 loratadine (C22H23ClN2O2) in the portion of Oral Solution taken by the formula: in which C is the concentration, in mg per mL, of USP Loratadine RS in the Standard preparation; and RU and RS are the ratios of loratadine to the internal standard peak responses obtained from the Assay preparation and the Standard preparation, respectively.