Multidimensional high-performance liquid chromatography has been used to analyze the structure of humic substances in Bayer liquor from an alumina separation plant. Separation has been achieved on a Phenomenex BioSep-S2000 size-exclusion column and a Phenomenex Synergi Polar-RP column. The results demonstrate a degree of resolution that previously could not be observed by more-conventional liquid chromatographic methods. In three fractions that were heart-cut from the BioSep-S2000 size-exclusion column in the first dimension, at least 18 components were resolved to baseline resolution in the second dimension, with many other peaks exhibiting less resolution. Analysis of these compounds by mass spectrometry showed that small molecules are present in fractions collected with relatively high apparent molecular weights, with the small molecules being held either in a supramolecular or micelle structure with larger molecules. Evidence is presented here that the latter is more likely.