The deconvolution of FTIR-ATR spectra to five Gaussians for detection of small changes in plant–water clusters

Abstract

This article presents a method that efficiently enables us to identify differences in the composition of water clusters. The Fourier transform infrared (FTIR) spectra in the O–H stretching region 2500 cm−1 to 4000 cm−1 of apple juice, raspberry juice, lyophilized water from apples (apple water), and lyophilized water from raspberry juice (raspberry water) were measured at a controlled temperature applying the Attenuated Total Reflection (ATR) sampling technique. The dependence of the IR spectra of ultra-pure water on temperature was also studied. Deconvolution to five Gaussians was used to demonstrate the absorption maxima of the spectra. The analysis of these deconvoluted spectra allows us to reveal the differences in the water clusters of different origin. The comparison of the deconvoluted FTIR-ATR spectra of apple and raspberry juices demonstrates that the application of such a method enables us to successfully evaluate the impact of different soluble solids occurred in juices on the composition of water clusters. The comparison of differences in the deconvoluted FTIR-ATR spectra of “apple water” and “raspberry water” with the deconvoluted spectra of ultra-pure water shows the suitability of such a method in the identification of changes in water clusters, where the total concentration of additives is as low as 20 ppm.