Change to read:
Identification—
A:
The IR absorption spectrum of a mineral oil dispersion of it, previously dried, exhibits maxima only at the same wavelengths as that of a similar dispersion of the residue prepared by dissolving 30 mg of
USP Dibucaine Hydrochloride RS in 5 mL of 0.5 N sodium hydroxide, extracting the resulting solution with 5 mL of ether, evaporating the ether, and drying the residue over phosphorus pentoxide.
B:
The retention time of the major peak in the chromatogram of the
Assay preparation corresponds to that in the chromatogram of the
Standard preparation, as obtained in the
Assay.
USP29
Chromatographic purity—
Proceed as directed for
Chromatographic purity under
Dibucaine Hydrochloride, except to use a
Test solution containing 36.2 mg of Dibucaine per mL: the principal spot obtained from the
Test solution corresponds in
RF value, color, and intensity to that obtained from the
Standard solution; the sum of the intensities of any secondary spots, if present in the chromatogram of the
Test solution, corresponds to not more than 2.0% of that of the principal spot in the chromatogram of the
Standard solution on the basis of comparison with the spots obtained from the
Comparison solutions.
Assay—
Mobile phase—
Dissolve 1.20 g of sodium lauryl sulfate, 0.20 g of sodium acetate, and 2.0 mL of triethylamine in 300 mL of water. Adjust with glacial acetic acid to a pH of 5.6, add 700 mL of methanol, mix, and pass through a suitable filter having a 0.5-µm or finer porosity. Make adjustments if necessary (see
System Suitability under
Chromatography 
621
).
Solvent mixture—
Prepare a mixture of methanol and water (70:30).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Dibucaine Hydrochloride RS in
Solvent mixture to obtain a solution having a known concentration of about 1 mg per mL. Pass through a suitable filter having a 0.5-µm or finer porosity.
Assay preparation—
Transfer about 90 mg of Dibucaine, accurately weighed, to a 100-mL volumetric flask, add Solvent mixture to volume, and mix. Pass through a suitable filter having a 0.5-µm or finer porosity.
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. The flow rate is about 1.5 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 1500 theoretical plates; the tailing factor for the analyte peak is not more than 3.0; and the relative standard deviation for replicate injections is not more than 2%.
Procedure—
Separately inject equal volumes (about 10 µL) of the
Standard preparation and the
Assay preparation into the chromatograph, record the chromatograms, and measure the area responses for the major peaks. Calculate the quantity, in mg, of C
20H
29N
3O
2 in the portion of Dibucaine taken by the formula:
(343.46/379.93)(100C)(rU / rS)
in which 343.46 and 379.93 are the molecular weights of dibucaine and dibucaine hydrochloride, respectively;
C is the concentration, in mg per mL, of
USP Dibucaine Hydrochloride RS in the
Standard preparation; and
rU and
rS are the responses of the dibucaine peaks obtained from the
Assay preparation and the
Standard preparation, respectively.
;)
and 66.0