Abstract
A rapid and accurate PMR procedure is described for the quantitation of xanthotoxin (8-methoxypsoralen) as a drug entity and in tablet dosage form. A standard deviation of 2.8% was obtained on 10 standard mixtures. The PMR spectrum, in addition, provides a very specific method for identification of xanthotoxin and detection of its biologically inactive isomer, bergapten (5-methoxypsoralen).