Characterization of Natural Organic Matter Using High Performance Size Exclusion Chromatography

High performance size exclusion chromatography (HPSEC) was used to obtain the molecular weight distributions of natural organic matter (NOM) from two South Australian drinking water sources. The NOM was separated into five nominal molecular weight fractions (30K) using ultrafiltration membranes prior to HPSEC analysis. The use of HPSEC as a tool for NOM characterization was compared with an independent method, flow field−flow fractionation (FlFFF), which separates molecules via a different mechanism. Unlike HPSEC, which uses a porous gel with a controlled pore size distribution to separate molecules, FlFFF uses hydrodynamic and molecular diffusion principles to separate molecules on the basis of molecular size, in the absence of a porous gel. The comparison was made using the following parameters: weight-average molecular weight (M w), number-average molecular weight (M n), peak molecular weight (M p), polydispersivity (M w/M n), and molecular weight range (80% confidence limits). Within the technical limitations of each method, good agreement was obtained between HPSEC and FlFFF for the different fractions. Although solute−gel interactions were identified with the HPSEC system, the validation of the technique with FlFFF indicates that HPSEC can provide useful and reliable molecular weight distributions of NOM in drinking water supplies.