Assay
Mobile phase
Prepare a filtered and degassed mixture of 530mLof water and 470mLof methanol containing about 6.35g of
dl-10-camphorsulfonic acid sodium salt and 0.8g of ammonium nitrate.Adjust with glacial acetic acid,if necessary,to a pHof between 5.0and 5.5.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Standard preparation
Dissolve an accurately weighed quantity of
USP Guanadrel Sulfate RSin
Mobile phaseto obtain a solution having a known concentration of about 10mg per mL.
Assay preparation
Transfer about 100mg of Guanadrel Sulfate,accurately weighed,to a container,add 10.0mLof Mobile phase,and mix.
Resolution solution
Dissolve suitable quantities of
USP Guanadrel Sulfate RSand ethylparaben in
Mobile phaseto obtain a solution having known concentrations of about 10mg and 12mg,respectively,in each mL.
Chromatographic system
(see
Chromatography á621ñ)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 1.5mLper 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 0.8for guanadrel and 1.0for 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 25µL)of the
Standard preparationand the
Assay preparationinto 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
4in the portion of Guanadrel Sulfate taken by the formula:
10C(rU/rS),
in which
Cis the concentration,in mg per mL,of
USP Guanadrel Sulfate RSin the
Standard preparation;and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.