Fractal analysis of FTIR spectra : Application to the characterization of amorphous carbohydrates

A method is proposed to allow quantification of the general aspect of infrared spectra as well as the observed changes due to structural modifications of sample. The method is based on fractal dimensions determination using a simple algorithm to perform the fractal analysis. Two fractal dimension for the infrared spectrum were determined: a "texture" fractal dimension, Dt, allowing quantification of the general shape of the spectrum and a "fine" fractal dimension, Df, permitting to follow the appearing of the small peaks generally associated with ordered states. The method was tested on amorphous and crystalline sucrose and on aqueous solutions of sucrose and trehalose at different concentrations in order to follow the changes in inter- and intra-molecular H - bonds in these disaccharides and to estimate the degree of order in these complex media. The fractal analysis seems to be a new useful tool allowing the exploitation of the fingerprint nature of infrared spectra and the quantification of the information provided by the general aspect of the infrared spectra.