Cross polarization and magic angle spinning carbon-13 nuclear magnetic resonance spectrometry for quantitative analysis of coal and coal-derived solids

The effects of contact time and pulse repetition time on the quantitative aspects of cross-polarization and magic angle spinning (CP/MAS) spectra of coals and coal-derived solid products were studied to determine optimal conditions for quantitative analysis. For a coal-derived solid product which was soluble in hexane, a value for carbon aromaticity (f/sub a/) from both the CP/MAS solid-state spectrum and the solution spectrum was derived. The studies show that the f/sub a/ value obtained at various times in the CP/MAS experiments should be closest to the real value. The optimum values for contact time and pulse repetition time must be determined for each sample to obtain a reliable measurement of f/sub a/.