USING MULTIVARIATE METHODS ON SOLID-STATE C-13 NMR DATA OF COMPLEX MATERIALS

Multivariate data analysis (MVA) has been used as an aid in the analys is and interpretation of C-13 NMR spectra in the solid state. The goal of this study was to investigate the effect of some important instrum ental parameters and calculation strategies on the outcome of the mult ivariate data analysis. The samples used were two peat forming plants, Sphagnum fuscum and Carer rostrata, incubated in four different redox environments. It was found that normalising each NMR spectrum to a co nstant area should be avoided. Using non-normalised data we get a slig htly better class separation and the peaks in the 'subspectra' are sha rpened. Depending on the relative size of interesting variation one sh ould be careful when choosing the number of variables, i.e. number of data points characterising each spectrum. The line broadening techniqu e should be used with great care in order not to obscure the informati on. We also suggest the use of the free induction decay (FID)/MVA dire ctly for classification purposes. This is a new approach to analyse th e output data from NMR measurements.