IDENTIFICATION OF PHOTOCHEMICAL OXIDATION-PRODUCTS OF 5,10,15,20-TETRA(M-HYDROXYPHENYL)CHLORIN BY ONLINE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY-ELECTROSPRAY IONIZATION TANDEM MASS-SPECTROMETRY

An on-line HPLC-electrospray ionization tandem mass spectrometry syste m has been developed for the separation and characterization of the ph otochemical oxidation products of 5,10,15,20-tetra (m-hydroxyphenyl)ch lorin (m-THPC), a new photodynamic therapeutic agent. m-THPC was photo -oxidized in methanol solution by exposure to white laboratory light f or one week. The products were then separated by isocratic elution on an Apex C-18 column with 0.1% trifluoroacetic acid in acetonitrile (23 :77, v/v) as mobile phase and characterized on-line by electrospray ta ndem mass spectrometry. The results showed the formation of 5,10,15,20 -tetra(m-hydroxyphenyl) porphyrin (m-THPP), hydroxy m-THPP and three h ydroxy m-THPC isomers. Hydroxylation on the reduced pyrrole ring of m- THPC was the most prominent reaction.