M. Amrhein et al., INFERRING CONCENTRATIONS ONLINE FROM NEAR-INFRARED SPECTRA - NONLINEAR CALIBRATION VIA MIDINFRARED MEASUREMENTS, Computers & chemical engineering, 20, 1996, pp. 975-980
Near-Infrared (NIR) spectroscopic methods for on-line concentration es
timation are gaining popularity in chemical production. The problem wi
th NIR data, however, is its nonlinear nature rendering standard facto
r-analytical (FA) techniques inapplicable to estimate the concentratio
ns. To infer concentrations on-line from NIR spectra, the following st
eps are proposed: (i) measure both the NIR and Mid-Infrared (MIR) spec
tra of unknown reaction mixtures in the laboratory (MIR spectroscopy h
as the desirable property of linearity with respect to concentrations)
, (ii) apply FA techniques to MIR data and infer concentrations, (iii)
calibrate NIR against the estimated concentrations by using standard
nonlinear regression methods and (iv) use the calibration model in sub
sequent production runs. Experimental results are presented to illustr
ate the efficiency of this method.