Methoxsalen Topical Solution
» Methoxsalen Topical Solution is a solution of Methoxsalen in a suitable vehicle. It contains not less than 9.2 mg and not more than 10.8 mg of methoxsalen (C12H8O4) per mL.
Packaging and storage— Preserve in tight, light-resistant containers.
USP Reference standards 11
USP Methoxsalen RS
Identification— Transfer a volume of Topical Solution to a 100-mL volumetric flask, and dilute quantitatively and stepwise with alcohol to obtain a concentration of about 8 µg per mL: the UV absorption 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) 611: between 66.5% and 77.0% of C2H5OH.
Mobile phase , Internal standard preparation, Standard preparation, and Chromatographic system—Prepare as directed in the Assay under Methoxsalen.
Assay preparation— Transfer an accurately measured volume of Topical Solution, equivalent to about 20 mg of methoxsalen, to a 100-mL volumetric flask. Dilute with alcohol to volume, and mix. Transfer 2.0 mL of this solution and 2.0 mL of Internal standard preparation to a 100-mL volumetric flask. Dilute with Mobile phase to volume, and mix. Pass through a 0.45-µm disk before using.
Procedure— Proceed as directed for Procedure in the Assay under Methoxsalen. Calculate the quantity, in mg, of methoxsalen (C12H8O4) in each mL of the Topical Solution taken by the formula:
5(C/V)(RU /RS)
in which V is the volume, in mL, of Topical Solution taken, and the other terms are as defined therein.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Feiwen Mao, M.S.
(MDOOD05) Monograph Development-Ophthalmics Oncologics and Dermatologicals
Reference Standards Lili Wang, Technical Services Scientist
USP32–NF27 Page 2932
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.