Methoxsalen Topical Solution
»Methoxsalen Topical Solution is a solution of Methoxsalen in a suitable vehicle.It contains not less than 9.2mg and not more than 10.8mg of methoxsalen (C12H8O4)per mL.
Packaging and storage— Preserve in tight,light-resistant containers.
Identification— Transfer a volume of Topical Solution to a 100-mLvolumetric flask,and dilute quantitatively and stepwise with alcohol to obtain a concentration of about 8µg per mL:the UVabsorption spectrum of this solution exhibits maxima and minima at the same wavelengths as that of a similar solution of USP Methoxsalen RS,concomitantly measured.
Alcohol content (if present)á611ñ: between 66.5%and 77.0%of C2H5OH.
Assay—
Mobile phase ,Internal standard preparation,Standard preparation,and Chromatographic system—Prepare as directed in the Assayunder Methoxsalen.
Assay preparation— Transfer an accurately measured volume of Topical Solution,equivalent to about 20mg of methoxsalen,to a 100-mLvolumetric flask.Dilute with alcohol to volume,and mix.Transfer 2.0mLof this solution and 2.0mLof Internal standard preparationto a 100-mLvolumetric flask.Dilute with Mobile phaseto volume,and mix.Pass through a 0.45-µm disk before using.
Procedure— Proceed as directed for Procedurein the Assayunder Methoxsalen.Calculate the quantity,in mg,of methoxsalen (C12H8O4)in each mLof the Topical Solution taken by the formula:
5(C/V)(RU/RS),
in which Vis the volume,in mL,of Topical Solution taken,and the other terms are as defined therein.
Auxiliary Information— Staff Liaison:Lawrence Evans,III,Ph.D.,Scientist
Expert Committee:(PA6)Pharmaceutical Analysis 6
USP28–NF23Page 1252
Phone Number:1-301-816-8389
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