Assay
Diluent
Prepare a mixture of water and methanol (1:1).
Mobile phase
Prepare a suitable mixture of water, acetonitrile, and methanol (60:20:20) containing 0.06% of sulfuric acid, 0.5% of sodium sulfate, and 0.02% of sodium 1-heptanesulfonate. The pH is about 2.6. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation
Dissolve an accurately weighed quantity of
USP Tetracaine Hydrochloride RS quantitatively in
Diluent to obtain a solution having a known concentration of about 1 mg per mL.
Resolution solution
Dissolve a quantity of salicylic acid in a portion of the Standard preparation to obtain a solution containing about 4 mg of salicylic acid and 1 mg of tetracaine hydrochloride per mL.
Assay preparation
Transfer an accurately measured volume of Injection equivalent to about 50 mg of tetracaine hydrochloride, to a 50-mL volumetric flask, dilute with Diluent to volume, and mix.
Chromatographic system
(see
Chromatography 621)The liquid chromatograph is equipped with a 305-nm detector and a 3.9-mm × 30-cm column containing packing L1. The flow rate is about 2 mL per minute. Chromatograph the
Resolution solution, and record the responses as directed for
Procedure: the relative retention times are about 0.8 for salicylic acid and 1.0 for tetracaine; and the resolution,
R, between the salicylic acid peak and the tetracaine peak is not less than 2. Chromatograph the
Standard preparation, and record the responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 5 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the areas for the major peaks. Calculate the quantity, in mg, of tetracaine hydrochloride (C
15H
24N
2O
2·HCl) in each mL of the Injection taken by the formula:
50(C / V)(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Tetracaine Hydrochloride RS in the
Standard preparation; V is the volume, in mL, of Injection taken; and
rU and
rS are the tetracaine peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.