Identification
Add a volume of Injection,equivalent to about 50mg of promethazine hydrochloride,to 20mLof dilute hydrochloric acid (1in 1000)contained in a separator.Wash the solution with a 20-mLportion of methylene chloride,discarding the washing.Add 2mLof 1Nsodium hydroxide and 20mLof methylene chloride,and shake for 2minutes.Evaporate the methylene chloride extract on a steam bath with the aid of a stream of nitrogen to dryness.Dissolve the residue in 4mLof carbon disulfide,filter through paper,if necessary,and determine the IRabsorption spectrum as directed under
IdentificationOrganic Nitrogenous Bases á181ñ,obtaining the spectrum of
USP Promethazine Hydrochloride RSas directed:the Injection meets the requirements of the test.
Assay
Mobile phase
Dissolve 1g of sodium 1-pentanesulfonate in 500mLof water,add 500mLof acetonitrile and 5mLof glacial acetic acid,filter,and degas.Make adjustments if necessary (see
System Suitabilityunder
Chromatography á621ñ).
Standard preparation
Dissolve an accurately weighed quantity of
USP Promethazine Hydrochloride RSin
Mobile phase,and dilute quantitatively,and stepwise if necessary,with the same solvent to obtain a solution having a known concentration of about 0.1mg per mL.
Assay preparation
Transfer an accurately measured volume of Injection,equivalent to about 50mg of promethazine hydrochloride,to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.Transfer 10.0mLof the resulting solution to a 100-mLvolumetric flask,dilute with Mobile phaseto volume,and mix.
System suitability preparation
Dissolve a suitable quantity of phenothiazine in Standard preparationto obtain a solution containing about 10µg of phenothiazine per mL.
Chromatographic system
(see
Chromatography á621ñ)The liquid chromatograph is equipped with a 254-nm detector and a 4.6-mm ×30-cm column that contains packing L11.The flow rate is about 1.5mLper minute.Chromatograph the
System suitability preparation,and record the peak responses as directed for
Procedure:the resolution,
R,between the promethazine and phenothiazine peaks is not less than 3.0,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure
Separately inject equal volumes (about 30µL)of the
Standard preparationand the
Assay preparationinto the chromatograph,record the chromatograms,and measure the responses for the major peaks.The relative retention times are 1.0for promethazine and about 1.6for phenothiazine.Calculate the quantity,in mg,of C
17H
20N
2S·HCl in each mLof the Injection taken by the formula:
500(C/V)(rU/rS),
in which
Cis the concentration,in mg per mL,of
USP Promethazine Hydrochloride 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.