Quantification of hydroxylic groups in a river humic substance by 29Si-NMR

Quantification of the hydroxylic functions of carboxylic, phenolic and alcoholic groups in a selected river humic substance (Ruhr/Germany) is performed by methylation/silylation and ²⁹Si-NMR analysis. The well known methylation/silylation procedure of Thorn et al. is modified by carrying out the diazomethane methylation in the presence of the proton catalyst p-toluene sulphonic acid. Additional experiments by both ¹³C-NMR-spectroscopy and potentiometric acid-base titration confirm the results obtained by ²⁹Si-NMR.