Assay
Mobile phase
Prepare a filtered and degassed mixture of 530 mL of water and 470 mL of methanol containing about 6.35 g of
dl-10-camphorsulfonic acid sodium salt and 0.8 g of ammonium nitrate. Adjust with glacial acetic acid, if necessary, to a pH of between 5.0 and 5.5. Make adjustments if necessary (see
System Suitability under
Chromatography 621).
Standard preparation
Dissolve an accurately weighed quantity of
USP Guanadrel Sulfate RS in
Mobile phase to obtain a solution having a known concentration of about 10 mg per mL.
Assay preparation
Transfer about 100 mg of Guanadrel Sulfate, accurately weighed, to a container, add 10.0 mL of Mobile phase, and mix.
Resolution solution
Dissolve suitable quantities of
USP Guanadrel Sulfate RS and ethylparaben in
Mobile phase to obtain a solution having known concentrations of about 10 mg and 12 mg, respectively, in each mL.
Chromatographic system
(see
Chromatography 621)The liquid chromatograph is equipped with a refractive index detector and a 4- to 4.6-mm × 25- to 30-cm stainless steel column containing packing L1. The flow rate is about 1.5 mL per minute. Chromatograph the
Resolution solution, and record the peak responses as directed for
Procedure: the resolution,
R, between guanadrel and ethylparaben is not less than 1.6, and the relative retention times are about 0.8 for guanadrel and 1.0 for ethylparaben. Chromatograph the
Standard preparation, and record the peak responses as directed for
Procedure: the relative standard deviation for replicate injections is not more than 2.5%.
Procedure
Separately inject equal volumes (about 25 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 (C
10H
19N
3O
2)
2·H
2SO
4 in the portion of Guanadrel Sulfate taken by the formula:
10C(rU / rS),
in which
C is the concentration, in mg per mL, of
USP Guanadrel Sulfate RS in the
Standard preparation; and
rU and
rS are the peak responses obtained from the
Assay preparation and the
Standard preparation, respectively.