A: Infrared Absorption 197K.

B: It responds to the tests for Chloride 191.

Mobile phase— Dissolve 1 g of tetraheptylammonium bromide in a 1-L mixture of a 1.5 g per L solution of sodium hydrogen sulfate, acetonitrile, and methanol (2:2:1). Make adjustments if necessary (see System Suitability under Chromatography 621).

System suitability solution— Transfer about 4 mg of USP Mefloquine Hydrochloride RS and 4 mg of USP Mefloquine Related Compound A RS to a 50-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix. [note—Mefloquine related compound A is threo-mefloquine.] Transfer 5.0 mL of this solution to a 100-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Test solution— Transfer about 0.10 g of Mefloquine Hydrochloride, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with Mobile phase to volume, and mix.

Diluted test solution— Transfer 1.0 mL of the Test solution to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix. Transfer 1.0 mL of this solution to a 20-mL volumetric flask, dilute with Mobile phase to volume, and mix.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 280-nm detector, a 4-mm × 2.5-cm precolumn, and a 4.0-mm × 25-cm column, both containing 5-µm packing L1. The flow rate is about 0.8 mL per minute. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.7 for mefloquine related compound A and 1.0 for mefloquine; the resolution, R, between mefloquine related compound A and mefloquine is not less than 2.0; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Equilibrate the column with Mobile phase at a flow rate of about 0.8 mL per minute for about 30 minutes. Inject 20 µL of Diluted test solution. Adjust the sensitivity of the system so that the height of the major peak is at least 50% of the full scale of the recorder. Separately inject equal volumes (about 20 µL) of the Test solution and Diluted test solution into the chromatograph, record the chromatogram for a time that is 10 times the retention time of the main peak, and measure the responses of all the peaks, excluding the main peak and any other peak producing a response of less than 0.2 times (0.02%) of the main peak in the chromatogram of the Diluted test solution. The response of the mefloquine related compound A peak in the Test solution with a relative retention time of about 0.7, with reference to the main peak, is not more than twice the area of the main peak in the chromatogram of the Diluted test solution (0.2%). The response of any other individual peak, other than the main peak in the chromatogram of the Test solution, is not greater than that of the main peak in the chromatogram of the Diluted test solution (0.1%); and the sum of the responses of any such peaks in the chromatogram of the Test solution is not greater than five times the response of the main peak in the chromatogram of the Diluted test solution (0.5%).