Evolving factor analysis (EFA) is a new approach to the resolution of individual component spectra on the basis of fluorescence lifetime differences. Phase-resolved fluorescence spectra collected at several excitation modulation frequencies are well suited to EFA resolution because the frequency-response curve of phase-resolved intensity for each lifetime component has a single, unique maximum. Unlike other self-modeling spectral matrix resolution methods, EFA has no fundamental limitation upon the number of components that can be resolved. In this work, the resolution of two-component and three-component mixtures of polycyclic aromatic hydrocarbons is demonstrated.
David W. Millican and Linda B. McGown, "Evolving Factor Analysis for Frequency-Domain Lifetime Resolution of Fluorescence Spectra," Appl. Spectrosc. 46, 28-33 (1992)