Fig. 1. Correlation spectroscopy (COSY) spectra of the fulvic acid acquired at 600 MHz. Standard COSY experiment (A), double quantum filtered correlation spectroscopy (DQF-COSY) (B), and expanded central region of the DQF-COSY highlighting couplings from sugars (C). Boxes 1 and 2 highlight regions where couplings from sugars and aromatic compounds in humic substances fall. The couplings in these structures tend to be close to the central diagonal. Note how the coupling information from these moieties is difficult to decipher in spectrum (A) but are clearly visible in spectrum (B).