Fig. 3From: Separation of acid-soluble constituents of soil humic acids by dissolution in alkaline urea solution and precipitation with acidSize exclusion chromatograms (UV detection at 280 nm; fluorescence detection at excitation 460 nm and emission 520 nm) of whole humic acid samples and their fractions normalized to the concentration of 100 mg carbon L−1. V 0 void volume, V 0 + V i total effective column volumeBack to article page