Assay—
0.0032M Hexanesulfonate buffer—
Mix 600mg of sodium 1-hexanesulfonate with water to obtain 1000mLof solution,adjust with phosphoric acid to a pHof 3.0±0.05,and filter.
Mobile phase—
Prepare a suitable degassed and filtered mixture of methanol and
0.0032M Hexanesulfonate buffer(7:3).Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Standard preparation—
Dissolve an accurately weighed quantity of
USP Metaraminol Bitartrate RSin water to obtain a solution having a known concentration of about 0.2mg of metaraminol per mL.
Assay preparation—
Transfer an accurately measured volume of Injection,equivalent to about 20mg of metaraminol,to a 100-mLvolumetric flask,dilute with water to volume,and mix.
System suitability preparation—
Prepare a solution of propylparaben in alcohol containing 0.4mg per mL.Mix 1volume of this solution with 99volumes of the Standard preparation.
Chromatographic system
(see
Chromatography á621ñ)—The liquid chromatograph is equipped with a 264-nm detector and a 4-mm ×25-cm column that contains packing L7.The flow rate is about 1mLper minute.Chromatograph the
System suitability preparationand the
Standard preparation,and record the peak responses as directed for
Procedure:the column efficiency is not less than 2600theoretical plates,the resolution,
R,between the metaraminol bitartrate and propylparaben peaks is not less than 3.0with propylparaben eluting first,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 10µL)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 metaraminol (C
9H
13NO
2)in each mLof the Injection taken by the formula:
100(C/V)(rU/rS),
in which
Cis the concentration,in mg per mL,of metaraminol represented by the
USP Metaraminol Bitartrate RSin the
Standard preparation;
Vis the volume,in mL,of Injection taken;and
rUand
rSare the peak responses obtained from the
Assay preparationand the
Standard preparation,respectively.