Identification—
A:
Infrared Absorption 
197F
.
B:
The retention time of the major peak in the chromatogram of the Test solution corresponds to that in the chromatogram of the System suitability solution, as obtained in the test for Limit of methamphetamine.
Limit of methamphetamine—
Mobile phase—
Prepare a filtered and degassed mixture of hexane, isopropyl alcohol, and acetonitrile (98:1.5:0.5). Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Resolution solution—
Mix suitable quantities of a solution of
USP Methamphetamine Hydrochloride RS in chloroform and
USP Levmetamfetamine RS in chloroform to obtain a solution containing about 0.025 mg per mL and 2.5 mg per mL of methamphetamine hydrochloride and levmetamfetamine, respectively. Transfer 2.0 mL of this solution to a suitable container, add 10 mg of 2-naphthyl chloroformate and 2.0 mL of chloroform, mix with a vortex mixer, and allow to stand for 5 minutes. To this solution, add 2 mL of 1 N sodium hydroxide, mix with a vortex mixer, allow to stand for 5 minutes, and discard the aqueous layer. Wash the organic layer twice with 2 mL of 1 N sodium hydroxide, discarding the aqueous layer. To the organic layer add 2 mL of 1 N hydrochloric acid, mix with a vortex mixer, and discard the aqueous layer. Wash the organic layer twice with 2 mL of 1 N hydrochloric acid, discarding the aqueous layer. To the organic layer add 2 mL of water, mix with a vortex mixer, and discard the aqueous layer. Wash the organic layer twice with 2 mL of water, discarding the aqueous layer. To the organic layer add about 1.0 g of anhydrous sodium sulfate, and mix with a vortex mixer. Transfer 1.0 mL of this solution to a 10-mL volumetric flask, dilute with
Mobile phase to volume, mix, and filter.
Test solution—
Transfer about 62.5 mg of Levmetamfetamine, accurately weighed, to a 25-mL volumetric flask, dissolve in and dilute with chloroform to volume, and mix. Transfer 2.0 mL of this solution to a suitable container, and proceed as directed in Resolution solution beginning with “add 10 mg of 2-naphthyl chloroformate and 2 mL of chloroform.”
Chromatographic system (see Chromatography 621)—
The liquid chromatograph is equipped with a 274-nm detector and a 4.6-mm × 25-cm column that contains packing L36. The flow rate is about 1.5 mL per minute. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the relative retention times are about 0.9 for methamphetamine and 1.0 for levmetamfetamine; and the resolution,
R, between methamphetamine and levmetamfetamine is not less than 1.4. Chromatograph the
Test solution, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Inject a volume (about 50 µL) of the
Test solution into the chromatograph, record the chromatogram, and measure the responses for the major peaks. Calculate the percentage of methamphetamine in the portion of Levmetamfetamine taken by the formula:
100rM / (rM + rL),
in which
rM is the methamphetamine peak response obtained from the
Test solution, and
rL is the peak response of levmetamfetamine obtained from the
Test solution: not more than 0.1% is found.
Limit of nonvolatile residue—
Heat about 1.0 g, accurately weighed, at 150
to constant weight: the limit is not more than 0.5%.
Ordinary impurities 466—
Test solution:
chloroform.
Standard solution:
chloroform.
Eluant:
a mixture of chloroform, cyclohexane, and diethylamine (5:4:1).
Visualization:
1.
Limits—
No impurity exceeds 0.1%, and the total does not exceed 0.5%.
Assay—
Transfer about 400 mg of Levmetamfetamine to a suitable container, add 50.0 mL of glacial acetic acid, and mix. Add two drops of
crystal violet TS, and titrate with 0.1 N perchloric acid VS. Perform a blank determination, and make any necessary correction. Each mL of 0.1 N perchloric acid is equivalent to 14.92 mg of C
10H
15N.
;)
-dimethyl-, (R)-.
)-(R)-N,