Michal Ritz

Identification of Clay Minerals by Infrared Spectroscopy and Discriminant Analysis

Identification of clay minerals based on chemometric analysis of measured infrared (IR) spectra was suggested. IR spectra were collected using the diffuse reflection technique. Discriminant analysis and principal component analysis were used as chemometric methods. Four statistical models were created for separation and identification of clay minerals. More than 50 samples of various clay mineral standards from different localities were used for the creation of statistical models. The results of this study confirm that the discriminant analysis of IR spectra of clay minerals could provide a powerful tool for identification of clay minerals. Differentiation of muscovite from illite and identification of mixed structures of illite–smectite were achieved.

Determination of the predominant minerals in sedimentary rocks by chemometric analysis of infrared spectra

The objective of the present study was to determine the predominant minerals in sedimentary rocks using Fourier-transform infrared (FTIR) spectroscopy and chemometric analysis. The chemometric analysis was performed on three types of sedimentary rock samples (claystones, clay slates, and sandstones), each with different predominant mineral components. Chemometric models were created to determine the major minerals of the rock samples studied — chlorite, muscovite, albite, and quartz. The FTIR spectra were obtained in transmission mode from pressed pellets of KBr-sample mixtures or by diffuse reflectance from hand-packed mixtures of samples with KBr. Spectral regions measured were 4000-3000 and 1300–400 cm-1, which contained important spectral information for the creation of the chemometric models. Principal component analysis was used in the chemometric method, with calibration models being created by a partial least-squares regression method. The mean relative error, standard error of prediction, and relative standard deviation were calculated for the assessment of accuracy, precision, and reproducibility. The value of the mean relative error was 15–20% for most of the calibration models; the value of the standard error of prediction was up to 6 w/w % for most of the calibration models. The values of the standard relative deviation ranged from ~2 to 8% for calibration models based on diffuse reflectance spectra whereas calibration models based on transmission spectra had values of relative standard deviation of ~15-20%.

Infrared and Raman spectroscopy of three commercial vermiculites doped with cerium dioxide nanoparticles

Three commercial vermiculites and these vermiculites doped with cerium dioxide nanoparticles were investigated by infrared and Raman spectroscopy. Infrared spectroscopy in middle infrared region (4000-400 cm-1) was supplemented by separation of overlapped spectral bands in the region of stretching vibration of hydroxyl groups. Detailed structural properties of vermiculites were completed based on the Raman spectroscopy in the spectral region between 800 and 100 cm-1 and X-ray diffraction analysis. Raman spectroscopy provided evidence of trioctahedral-dioctahedral vermiculite-mica in original vermiculite and trioctahedral phyllosilicate structures in vermiculites after precipitation procedure of cerium dioxide nanoparticles. The wavenumber shifts of the Raman bands at about 670 cm-1 and 190 cm-1 in spectra of vermiculites showed strong trend with increasing Fe3+ and Al substitution in tetrahedra and octahedra, respectively.