A designed experiment for the examination of techniques used in the analysis of near infrared spectra. Part 1. Analysis of spectral structure

Abstract

To assess the effectiveness of several statistical techniques to detect the known structure of sample spectra, a factorially designed experiment was carried out using mixtures of four pure chemicals. Analyses of the variation between spectra as expressed by correlation graphs and principal components are shown to be powerful techniques for relating the spectra of constituents to those of samples. A method of interpreting correlation graphs is proposed that identifies the existence of dominant effects such as particle size variation. For these samples, a standardisation algorithm was shown to reduce interference effects due to particle size and to allow easier interpretation of both correlation graphs and principal components.