RESOLUTION OF INFRARED-SPECTRA OF MIXTURES OF POTENTIAL ORGANIC WORKPLACE POLLUTANTS BY FACTOR-ANALYSIS

A new approach for factor analysis of MIR spectra is proposed and appl ied to 15 mixtures of three potential workplace pollutants. PCA is per formed on small regions of the overall experimental data matrix consis ting of omega spectral frequencies and 15 spectra. The window is moved across the spectral data set, and the number of significant component s in each window is computed. Regions where only one component absorbs ('composition one') are then identified. Correlations between the abs tract concentration profiles for these points are used to sort the com position one regions into three groups. Each group represents a single component. Elimination of one of these groups permits new orthogonal spectra to be computed consisting of two components. The process is fu rther repeated to yield one pure spectrum. Choosing and eliminating di fferent groups allows the other pure spectra to be revealed. For corre ct choice of window size, the recovery of the pure spectra is good. It is shown that combination of orthogonal loadings spectra is mathemati cally equivalent to rotation as used in evolutionary factor analysis i n HPLC.