More detailed description of the algorithm can be found elsewhere. Briefly, the number of components can be estimated from singular value decomposition (SVD). The procedure needs an initial estimate of either C or S T . The initial C matrix can be generated using Evolving Factor Analysis (EFA), which is a local rank analysis method, very appropriate to obtain initial estimates of concentration profiles from sequential evolutionary processes. The resolved profiles in C and S T are not unique, being subject to rotational ambiguity. Constraints are therefore used to limit the span of feasible solutions and to provide chemically meaningful concentration profiles and resolved spectra. All figures were prepared using Matlab, Excel, SigmaPlot or OriginPro softwares.