A: Infrared Absorption 197K.

B: It responds to the tests for Chloride 191.

Test solution: 20 mg per mL, in water.

Test solution: chloroform.

Standard solution: chloroform.

Eluant: a mixture of chloroform, cyclohexane, and diethylamine (5:4:1).

Visualization: 1.

Mobile phase— Prepare a degassed solution of 1.1 g of sodium 1-heptanesulfonate in a mixture of water, methanol, and diluted glacial acetic acid (7 in 50) (575:400:25). Adjust with the addition of acetic acid to a pH of 3.3 ± 0.1, if necessary. Filter through a 0.5-µm disk. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Methamphetamine Hydrochloride RS in 0.12 M phosphoric acid, and dilute quantitatively and stepwise, with the aid of sonication if necessary, with 0.12 M phosphoric acid to obtain a solution having a known concentration of about 0.2 mg per mL.

Assay preparation— Transfer about 20 mg of Methamphetamine Hydrochloride, accurately weighed, to a 100-mL volumetric flask, dissolve in and dilute with 0.12 M phosphoric acid to volume, and mix.

Chromatographic system (see Chromatography 621)—The liquid chromatograph is equipped with a 257-nm detector and a 3.9-mm × 30-cm column that contains packing L1. The flow rate is about 2 mL per minute. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the column efficiency determined from the analyte peak is not less than 1000 theoretical plates; the tailing factor for the analyte peak is not more than 1.5; and the relative standard deviation for replicate injections is not more than 2.0%.

Procedure— Separately inject equal volumes (about 20 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 C10H15N·HCl in the portion of Methamphetamine Hydrochloride taken by the formula: in which C is the concentration, in mg per mL, of USP Methamphetamine Hydrochloride RS in the Standard preparation; and rU and rS are the peak responses obtained from the Assay preparation and the Standard preparation, respectively.