KINETIC SPECTROPHOTOMETRIC RESOLUTION OF BINARY-MIXTURES USING 3-WAY PARTIAL LEAST-SQUARES

Three-way partial least squares (PLS) was applied to kinetic-spectroph otometric data. The coupling reaction of diazotized sulfanilamide with o-, m- and p-amino benzoic acid (ABA), and with orciprenaline (ORC), to give azodyes was monitored. Three binary mixtures of substrates, i. e., o-ABA/ORC, m-ABA/p-ABA and o-ABA/m-ABA, with different values of t he rate constant ratio and spectra which overlapped seriously were stu died. The spectra of the mixtures were scanned with a 2 nm resolution every 30 s during ca. 15 min. The data sets contained from 30 X 36 to 30 X 48 time-wavelength data. Nine mixtures of each binary combination of substrates were used for calibration, thus the three-way calibrati on data sets contained from 9 X 30 X 36 to 9 X 30 X 48 concentration-t ime-wavelength data. The two-way PLS modelling was constructed on the basis of single wavelength kinetic curves, and the three-way PLS model ling was applied to series of three-way data arrays consisting of a nu mber of selected wavelengths each (up to the whole spectra). The resul ts based on three-way data arrays were better than that of ordinary PL S, particularly with mixtures having both a low rate constant ratio an d small spectral differences.