Assay
Solvent A
Dissolve 1.9 g of sodium 1-hexanesulfonate in 700 mL of water, add 50 mL of 1 M monobasic sodium phosphate and 20 mL of 0.25 N triethylammonium phosphate (prepared by mixing 500 mL of a solution containing 25.3 g of triethylamine and 500 mL of a solution containing 9.6 g of phosphoric acid), and mix. Dilute with water to 1 L, and mix.
Mobile phase
Prepare a filtered and degassed mixture of
Solvent A and methanol (100:82). Make adjustments if necessary (see
Chromatography 621).
Standard preparation
Dissolve an accurately weighed quantity of
USP Phenylpropanolamine Hydrochloride RS in methanol, and quantitatively dilute with methanol to obtain a solution having a known concentration of about 375 µg per mL.
Assay preparation
Weigh and finely powder not fewer than 20 Tablets. Transfer an accurately weighed portion of the powder, equivalent to about 750 mg of phenylpropanolamine hydrochloride, to a 200-mL volumetric flask. Add about 150 mL of methanol and sonicate for about 10 minutes. Dilute with methanol to volume, and mix. Transfer 10.0 mL of this solution to a 100-mL volumetric flask, dilute with methanol to volume, and mix. Use a filtered portion of the solution.
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 tailing factor for the analyte peak is not more than 2.5, and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Inject an accurately measured volume (about 70 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 phenylpropanolamine hydrochloride (C
9H
13NO·HCl) in the portion of Tablets taken by the formula:
2C(rU / rS),
in which
C is the concentration, in µg per mL, of
USP Phenylpropanolamine Hydrochloride RS; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.