No abstract

Thermal-induced infrared emission spectroscopy is reviewed, with emphasis on developments in theory and experiment. The theory associated with obtaining thermal-induced infrared emittance spectra as a function of sampling optics is discussed. The FT-IR configuration and data reduction methods needed to properly obtain high-quality spectra, close to room temperature, are also considered. Optical and experimental parameters which affect the spectrum are demonstrated by example, with a discussion of methods which optimize the signal-to-noise ratio. The applications shown range from polymer films on both metal and semiconductor surfaces to a single filament analyzed by micro-emission spectroscopy.

No abstract

The principal component regression (PCR) and partial least-squares (PLS) methods are used to calibrate and validate models for quantitative prediction of the composition of mixtures from FT-IR spectra. An experimental system of two- and three-component mixtures of xylene isomers was sampled with the use of statistical experimental designs. For two-component mixtures, the prediction error of independent validation samples decreased with increasing numbers of design points in the calibration. Four design points were needed to achieve a prediction accuracy of 0.0013 weight fraction. For three-component mixtures, a Scheffé {3,3} simplex lattice design, which has ten design points, achieved an equivalent accuracy of 0.002 weight fraction. There was little difference in performance between PLS and PCR computations. The results demonstrate the application of statistical methodology to the calibration of infrared spectra and show the importance of including an adequate number of samples in the calibration. The F test on the residual spectrum is shown to be a valuable tool for the identification of spurious data.

The feasibility of obtaining FT-Raman spectra of consumer products inside clear polymeric packaging is described. It is possible to obtain high-quality spectra of the sample without removing it from the package, thus enabling quality-control checks to be performed on a final product. Examples are shown for three pharmaceutical preparations and one food product.