Fulvic acid 'backbone' structures were studied by subjecting fulvic acids isolated from Elliott soil, Suwannee River and Waskish peat to a selective reduction method. The products were subsequently analysed using gas chromatography and gas chromatography-mass spectrometry. The reducing agent was n-butylsilane in the presence of tris(pentafluorophenyl)borane, the latter serving as a Lewis acid catalyst. The method is the first chemical degradation method able to reduce the polar groups of fulvic acids without destroying any 'core' structural information. The degradation method also enables reduction of polycarboxylic acids, alcohols, aldehydes, ketones and methyl esters to alkanes, with phenols being converted to silyl ethers. Ester linkages are reduced to ethers and ethers are unaffected.