Identification—
A:
Dissolve about 300 mg in 5 to 10 mL of water in a separator, add 4 mL of 6 N ammonium hydroxide, and extract with four 15-mL portions of chloroform. Combine the chloroform extracts, evaporate with the aid of a current of warm air, and dry the residue in vacuum over silica gel for 24 hours: the crystalline precipitate so obtained responds to the
Identification tests under
Lidocaine.
B:
Its solutions respond to the tests for
Chloride 
191
.
Sulfate—
Dissolve about 200 mg in 20 mL of water, add 2 mL of 3 N hydrochloric acid, mix, and divide into two parts. To one part of the solution add 1 mL of
barium chloride TS: no more turbidity is produced than is present in the remaining portion of the solution to which nothing has been added.
Other requirements—
Where the label states that Lidocaine Hydrochloride is sterile, it meets the requirements for
Sterility Tests 71 and for
Bacterial endotoxins under
Lidocaine Hydrochloride Injection. Where the label states that Lidocaine Hydrochloride must be subjected to further processing during the preparation of injectable dosage forms, it meets the requirements for
Bacterial endotoxins under
Lidocaine Hydrochloride Injection.
Change to read:
Assay—
Mobile phase—
Mix 50 mL of glacial acetic acid and 930 mL of water, and adjust with 1 N sodium hydroxide to a pH of 3.40. Mix about 4 volumes of this solution with 1 volume of acetonitrile, so that the retention time of lidocaine is about 4 to 6 minutes. Pass through a membrane filter having a 1-µm or finer porosity, and degas. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation—
Dissolve about 85 mg of
USP Lidocaine RS, accurately weighed, with warming if necessary, in 0.5 mL of 1 N hydrochloric acid in a 50-mL volumetric flask, dilute with
Mobile phase to volume, and mix to obtain a
Standard preparation having a known concentration of about 1.7 mg of lidocaine per mL.
Assay preparation—
Transfer about 100 mg of Lidocaine Hydrochloride, accurately weighed, to a 50-mL volumetric flask, dilute with Mobile phase to volume, and mix.
Resolution preparation—
Prepare a solution of methylparaben in Mobile phase containing about 220 µg per mL. Mix 2 mL of this solution and 20 mL of the Standard preparation.
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.
USP29 The flow rate is about 1.5 mL per minute. Chromatograph about 20 µL of the
Resolution preparation, and record the peak responses as directed for
Procedure: the resolution,
R, between lidocaine and methylparaben is not less than 3.0. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 1.5%.
Procedure—
Separately inject equal volumes (about 20 µL) of the
Assay preparation and the
Standard preparation into the chromatograph. Record the chromatograms, and measure the responses for the major peaks. Calculate the quantity, in mg, of C
14H
22N
2O·HCl in the portion of Lidocaine Hydrochloride taken by the formula:
(270.80/234.34)(50C)(rU / rS)
in which 270.80 and 234.34 are the molecular weights of lidocaine hydrochloride and lidocaine, respectively;
C is the concentration, in mg per mL, of
USP Lidocaine RS in the
Standard preparation; and
rU and
rS are the lidocaine peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.
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