Determination of 8-methoxypsoralen in plasma by electron capture gas chromatography

A method is given for the determination of 8-methoxypsoralen in human plasma at the low ng/ml level using gas chromatography with electron capture detection. 8-Methoxypsoralen was extracted from plasma with methylene chloride at pH 7.0. After addition of the internal standard, 8-butoxypsoralen, the psoralens were hydrolysed in sodium hydroxide and the aqueous phase was purified by extraction with methylene chloride and toluene. The aqueous phase was acidified and the re-lactonized psoralens were extracted with toluene and analysed. Some determinations of plasma levels of 8-methoxypsoralen after oral administration are presented.