A: The retention time exhibited by methoxsalen in the chromatogram of the Assay preparationcorresponds to that of methoxsalen in the chromatogram of the Standard preparationas obtained in the Assay.

B: Place one capsule in 50mLof alcohol contained in a high-speed glass blender jar and blend thoroughly until the shell is completely dispersed.Dilute a portion quantitatively with alcohol to obtain a solution having a concentration of about 4µg per mL:the UVabsorption spectrum of the solution so obtained exhibits maxima and minima at the same wavelengths as that of a similar solution of USP Methoxsalen RS,concomitantly measured.

FORSOFT GELATIN CAPSULES—

FOR HARD GELATIN CAPSULES—

Mobile phase— Prepare a filtered and degassed mixture of acetonitrile and water (65:35).Make adjustments if necessary (see System Suitabilityunder Chromatography á621ñ).

Internal standard solution— Prepare a solution of trioxsalen in alcohol having a known concentration of 0.2mg per mL.

Standard preparation— Prepare a solution in alcohol having an accurately known concentration of 0.2mg of USP Methoxsalen RSper mL.Pipet 2.0mLof this solution into a 100-mLvolumetric flask containing 2.0mLof Internal standard solution,dilute with Mobile phaseto volume,and mix.

Assay preparation— Place not less than 10Capsules in a high-speed glass blender jar containing 100.0mLof alcohol,and blend thoroughly.Transfer an accurately measured volume of the aliquot from the blender jar,equivalent to about 2mg of Methoxsalen,to a 50-mLvolumetric flask containing 10.0mLof Internal standard solution,dilute with alcohol to volume,mix,and filter.Transfer 5.0mLof this solution to a 50-mLvolumetric flask,dilute with Mobile phaseto volume,mix,and filter.

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 peak and internal standard peak 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 0.5for Methoxsalen and 1.0for Trioxsalen.Calculate the quantity,in mg,of methoxsalen (C12H8O4)per Capsule taken by the formula: in which Cis the concentration,in mg per mL,of USP Methoxsalen RSin the Standard preparation;Vis the volume,in mL,of Assay preparationtaken;and RUand RSare the peak response ratios obtained from the Assay preparationand the Standard preparation,respectively.