Principal component global analysis of fluorescence and absorption spectraof 2-(2 '-hydroxyphenyl)benzimidazole

Principal component analysis (PCA) of a series of absorption and emission s pectra of 2-(2'-hydroxyphenyl)benzimidazole (HBI) in aqueous solutions in t he PH range from 1.11 to 12.3 and 3.85 to 9.62, respectively, reveals the p resence of three contributing components both in the ground and in the exci ted state. The combination of PCA with global analysis (PCGA) confirms the previously proposed reaction mechanism and allows the determination of pK(a ) values, pure component spectra, and concentration profiles of the ground- and excited-state species in spite of their strong spectral overlap. PCGA is proved to be a powerful complement to standard nonlinear least-squares a nalysis of physicochemical systems.