Separation of overlapping spectra from evolving systems using factor analysis 3. Fluorescence spectra of hematoporphyrin IX di-n-propylether diethanolamide

Abstract

Fluorescence spectroscopy of hematoporphyrin IX di-n-propylether diethanolamide (HPPEEA) in aqueous solutions, with and without SDS, was obtained in the pH range from 0.1 to 13. At pH greater than 3, HPPEEA in water solutions gives spectra complicated by aggregation whereas in aqueous SDS solutions, the aggregation is greatly reduced. Factor analysis is used to separate the spectra of the individual species from the experimental spectra. Five and four species are identified in pure water and in aqueous SDS solutions, respectively. The predominant species are: two free bases at pH higher than 6; one monocation at pH near 4; and two or one dications at pH lower than 2.5. The intensity signatures are related to the ionic distribution and to the aggregation situation of HPPEEA at different pH.