QUANTITATIVE-DETERMINATION OF SULFUR-OXYGEN ANION CONCENTRATIONS IN AQUEOUS-SOLUTION - MULTICOMPONENT ANALYSIS OF ATTENUATED TOTAL REFLECTANCE INFRARED-SPECTRA

The multicomponent analysis of FT-IR attenuated total internal reflectance spectra of mixtures of sulfur-oxygen anions provides an accurate noninvasive method for their quantitation. The use of spectral artifact basis functions obtained from the singular value decomposition of a difference spectra matrix results in a marked increase in accuracy. Further improvements in accuracy are attained with the use of multicomponent spectra as basis functions. The analysis of a series of solutions of sulfur-oxygen anions ranging in concentration from 0.0005 to 0.0323 M resulted in a root-mean-square error of 0.0002 M. In an in situ experiment in which the anaerobic decomposition of aqueous sodium dithionite was observed in ca. 1.5-min intervals over a 30-min period, the method was shown to account continuously for total sulfur and average oxidation state while simultaneously measuring the concentrations of seven components at each interval.