The paper discusses the usefulness of self modelling multivariate curve resolution (nonnegative matrix factorization) as a chemometric tool for the analysis of inhomogeneous spots captured by densitometer in multivariate way. The discussion is based on two examples: a spot of decomposed aspirin with comparative spot of pure salicylic acid, and spots of overlapped ciprofibrate and clofibric acid. It is concluded that this approach works well in the case of thin-layer chromatography (TLC) and the algorithm finds reliable spectral and concentration profiles, even with high overlap and spectral similarity. Nonlinearity does not affect this algorithm in visible manner. The computation can be performed with free software and can be recommended as good method to analyze inhomogeneity and to obtain additional proof of spot contamination with estimates of the spectral profiles.
K. Ferenczi-Fodor, Z. Végh, B. Renger, Trends Anal. Chem. 25 (2006) 778–789.