Size-exclusion chromatographic descriptors of humic substances

An approach to the generation of size exclusion chromatographic (SEC) descriptors of humic substances (HS) is proposed. It implies a calculation of initial, central and normalised statistical moments and some of their ratios from the raw SEC-data. The proposed descriptors extend the pool of common molecular weight (MW) characteristics (average MW's and their ratios) up to 20 parameters, which is important for the purposes of classification and prognostic modelling. Original software was developed to facilitate the computation of molecular weight distribution (MWD) and SEC-descriptors of HS from raw chromatographic data. The developed approach was applied to two model compounds and three humic materials. The discriminatory power of the calculated descriptors was roughly estimated on the example of three humic materials of different origin with the use of a multivariate variance analysis. Weight average MW and a ratio of the z- to weight average distribution coefficients were found to be the best discriminators, whereas the significance level of discrimination provided by the second moment and M-z/M-w-ratio was lower than 95%. (C) 2000 Elsevier Science B.V. All rights reserved.