Identification and quantification of 16 inorganic ions in water by Gaussian curve fitting of near-infrared difference absorbance spectra.

This study shows two novel fitting strategies applied to differential absorbance spectra for identification and quantification of electrolytes. The effects of 16 dissolved salts were investigated in the wavelength range from 14000 to 9091 wavenumbers (714-1100 nm) by linear fits of the differential absorbance values (Y(υ,c)=offset(υ)+b(υ)×c) recorded for each wavenumber (υ) and concentration (c) ranges from 500 to 30 mM. The slopes (b) of these fits resulted in clear fingerprints of the electrolytes. A narrow bandwidth (10754-9618 wavenumbers) sensor can be created using truth tables resulting from the Gaussian curve fitting method.