Effect of paramagnetic iron on quantitation in carbon-13 cross polarization magic angle spinning nuclear magnetic resonance spectrometry of heterogeneous environmental matrices

/sup 13/C solid state cross polarization magic angle spinning (CPMAS) spectra and proton relaxation parameters of model sludge components and derived mixtures were examined. Relative magnetization responses of lipid, carbohydrate, protein, and lignin components as well as their proton T/sub 1/ (spin-lattice relaxation times) and T/sub 1rho/ (rotating frame spin-lattice relaxation times) values were evaluated in the presence of paramagnetic Fe/sup 3 +/ at levels found in whole sludge samples. Significant reductions in proton T/sub 1/ and T/sub 1rho/ values were observed specifically in the hydrophilic components, suggesting that intimate contact of paramagnetic centers is felt through the more acidic exchangeable proton sites. Samples from each stage of the Beltsville sludge composting process were examined for total carbon content, composition, and the effect of paramagnetic metal by their /sup 13/C CPMAS spectra and proton relaxation times. Increases in residual lignified and aromatic components were followed by application of an interrupted decoupling sequence.