The polybutylene terephthalate (PBT) concentration and intrinsic viscosity of polycarbonate (PC) polymer blends were determined by means of near-infrared (NIR) reflectance and absorption spectrometry coupled with multiple regression analysis. The cross-search method was used in the selection of analytical wavelengths, whereas the correctness of the determinations was confirmed by cross validation. The correlation coefficients between the reference and NIR-determined values for the reflectance and absorption techniques were 0.979 and 0.955, respectively. The apparent number of orthogonal degrees of freedom in the polymer standards was affected by the number of samples employed in the NIR regression analysis.
Chu Zhu and Gary M. Hieftje, "Near-Infrared Analysis of Chemical Constituents and Physical Characteristics of Polymers," Appl. Spectrosc. 46, 69-72 (1992)