Absorption band Principal component analysis

Ohta, N., Estimating absorption bands of component dyes by means of principal component analysis, Anal. Chem., 45, 553-557, 1973. 

Changes in wheat carbohydrate chemistry due to chemical enzymatic degradation were measured on a macro scale by internal reflection (attenuated total reflection ATR) FT-IR spectroscopy from a spot size of 250 X 250 gm [51]. In this study, the absorption bands of sucrose, fructose, glucose, arabinose and galactose were identified, and spectra included for mahogany, huckleberry and oak, as well as for cellulose and cellophane. Both, principal component analysis (PCA) and plotting of PCI versus PC2 enabled distinctions to be made between filter paper, cello-... 

The distinctive absorption bands associated with individual molecules enable the analysis of individual components in even complex mixtures by either evaluating isolated bands or by applying modern chemometric methods (e.g. Principal compound analysis), which process the entire spectral information. As a consequence, mid-IR spectroscopy represents a widely applicable tool for investigations of dynamic processes (e.g. chemical reactions, phase transitions, sedimentations, etc.). Moreover, information about interactions of the analyst with the surrounding media can be acquired because vibrational modes tend to be affected by the molecule s environment (Raichlin Katzir, 2008). 

For mixtures of several nucleotides and/or nucleosides, however, spectroscopic analyses become difficult because UV spectra contain only a small number of absorption bands and have a very similar shape. In these cases, it is necessary to evaluate precisely and in detail the minor differences in the spectra, such as the position of the shoulders and the relative intensities of the various bands, which are often sufficient for multicomponent analysis. Two approaches, the so-called principal component regression (PGR) and partial least-squares (PLS) regression analyses, with Fourier preprocessing of UV spectra, have been developed. These methods can monitor continuously entire spectral regions, and they are generally reliable and accmate. They have allowed the composition of 14 unknown mixtures of dAMP, dCMP, dGMP, and dTMP to be analyzed, with average per cent errors of 0.60-1.85%. The presence of a protein... 

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