DOES ULTRASONIC DISPERSION AND HOMOGENIZATION BY BALL-MILLING CHANGE THE CHEMICAL-STRUCTURE OF ORGANIC-MATTER IN GEOCHEMICAL SAMPLES - A CPMAS C-13 NMR-STUDY WITH LIGNIN

Ultrasonic dispersion of geochemical samples suspended in water and su bsequent homogenization by ball milling is widely used for fractionati on of organic matter. The effect of these treatments on organic matter is investigated with lignin as a model compound. Structural alteratio ns detectable by solid-state C-13 nuclear magnetic resonance (NMR) spe ctroscopy were examined. Comparison of the solid-state C-13 NMR spectr a of untreated lignin and lignin mixed with quartz or soil did not rev eal evidence for structural changes in the organic matter composition after ultrasonic dispersion and subsequent ball-milling. The chemical structure of organic matter in geochemical samples is not affected by these treatments as far as such structural alterations can be detected by solid-state C-13 NMR spectroscopy. (C) 1997 Elsevier Science Ltd.