Methoxsalen
;)
7H-Furo[3,2-g][1]benzopyran-7-one,9-methoxy-.
9-Methoxy-7H-furo[3,2-g][1]benzopyran-7-one [298-81-7].
»Methoxsalen contains not less than 98.0percent and not more than 102.0percent of C12H8O4,calculated on the anhydrous basis.
Packaging and storage—
Preserve in well-closed,light-resistant containers.
Identification,Infrared Absorption á197Kñ.
Water,Method Iá921ñ:
not more than 0.5%.
Residue on ignition á281ñ:
not more than 0.1%,a 1-g specimen being used.
Heavy metals,Method IIá231ñ:
0.002%.
Chromatographic impurities—
Prepare a solution of it in chloroform containing about 20mg per mL(Solution A).Dilute 1.0mLof it with chloroform to 100.0mL(Solution B).Apply 5-µLportions of both solutions at points along a line about 2.5cm from one edge of a thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel mixture and previously dried at 105
for 30minutes.Develop the plate in a suitable chamber,without previous equilibration,using a mixture of 9volumes of benzene and 1volume of ethyl acetate,until the solvent front has moved to about 15cm above the line of application.Remove the plate from the chamber,air-dry,and observe under long-wavelength UVlight:any spot in the chromatogram from Solution A,other than the principal spot,is not more intense than the spot from Solution B(1.0%).
for 30minutes.Develop the plate in a suitable chamber,without previous equilibration,using a mixture of 9volumes of benzene and 1volume of ethyl acetate,until the solvent front has moved to about 15cm above the line of application.Remove the plate from the chamber,air-dry,and observe under long-wavelength UVlight:any spot in the chromatogram from Solution A,other than the principal spot,is not more intense than the spot from Solution B(1.0%).
Organic volatile impurities,Method Vá467ñ:
meets the requirements.
Solvent—
Use dimethyl sulfoxide.
Assay—
Mobile phase—
Prepare a solution of acetonitrile in water (35in 100).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).
Internal standard preparation—
Dissolve trioxsalen in alcohol to obtain a solution containing about 0.2mg per mL.
Standard preparation—
Using an accurately weighed quantity of USP Methoxsalen RS,prepare a solution in alcohol having a known concentration of about 0.2mg per mL.Transfer 2.0mLof this solution to a 100-mLvolumetric flask,add 2.0mLof Internal standard preparation,dilute with Mobile phaseto volume,and mix to obtain a Standard preparationhaving a known concentration of about 4µg of USP Methoxsalen RSper mL.Pass through a 0.45-µm disk before using.
Assay preparation—
Using 20mg of Methoxsalen,accurately weighed,proceed as directed for Standard preparation.
Chromatographic system
(see Chromatography á621ñ)—The liquid chromatograph is equipped with a 254-nm detector and a 4-mm ×30-cm column that contains packing L1.The flow rate is about 1.5mLper minute.Chromatograph the Standard preparation,and record the peak responses as directed for Procedure:the resolution,R,between the analyte and internal standard peaks is not less than 4.0,and the relative standard deviation for replicate injections is not more than 2.0%.
Procedure—
Separately inject equal volumes (about 20µL)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 about 2.1for trioxsalen and 1.0for methoxsalen.Calculate the quantity,in mg,of C12H8O4,in the portion of Methoxsalen taken by the formula:
5C(RU/RS),
in which Cis the concentration,in µg per mL,of USP Methoxsalen RSin the Standard preparation;and RUand RSare the ratios of the peak responses of methoxsalen to the internal standard obtained from the Assay preparationand the Standard preparation,respectively.
Auxiliary Information—
Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 1251
Phone Number:1-301-816-8389