Discrimination of Commercial Natural Mineral Waters Using near Infrared Spectroscopy and Principal Component Analysis

To obtain fundamental knowledge on the development of micro analyses for constituents in water, the discrimination of three varieties of commercial natural mineral water, ultra pure water and deionised water, was attempted using near infrared (NIR) spectroscopy. Both the original NIR spectra and their second derivatives were almost identical to each other for these five types of water and it was difficult to discriminate between their spectra visually. However, the use of discriminant analysis enabled the five kinds of waters to be distinguished. Principal component analysis for the second derivative spectra revealed that the independent variables of the discriminant analysis were identical with the wavelength regions affected by ionic hydration. For the discrimination of water, the original spectra were more suitable than the second derivative spectra because the baseline variation of the original spectra had the useful information for the analysis.