In near-infrared reflectance analysis (NIRA), a computer is trained to recognize and quantitate the relationship between the near-infrared spectrum of a sample and the concentrations of one or more of the sample constituents. During this training process the computer implicitly generates the spectrum of the constituents in question, although this spectrum is ordinarily not available for operator inspection. In the present study, a method for displaying this implicit information is developed and evaluated. The resulting "reconstructed spectrum" can be of a specific chemical constituent in a sample or can be a composite spectrum of those components that collectively contribute to specific sample properties such as material strength or processing temperature, or to sensory characteristics such as the "hotness" of peppers. A comparison is made of this new spectral reconstruction technique to established methods such as spectral stripping and factor analysis.
D. E. Honigs, G. M. Hieftje, and T. Hirschfeld, "A New Method for Obtaining Individual Component Spectra from Those of Complex Mixtures," Appl. Spectrosc. 38, 317-322 (1984)