Analytical Sciences

Optimization of Conditions for High-Performance Size-Exclusion Chromatography of Different Soil Humic Acids

Daichi ASAKAWA,* Takuro KIYOTA,** Yukiko YANAGI,* and Nobuhide FUJITAKE*

*The Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
**The Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan

A method of high-performance size-exclusion chromatography (HPSEC) for a wide variety of soil humic acids (HAs) was developed. Two types of soil HAs (Cambisol and Andosol HAs), which have substantially different chemical properties, showed different effects of salt and organic solvent concentrations in the eluent on chromatograms. A Shodex OHpak SB-805 HQ column with 10 mM sodium phosphate buffer (pH 7.0) containing 25% of acetonitrile (v/v) was found to be applicable for different HAs, and showed high reproducibility and recovery (87.0 - 94.5%). The Cambisol HA was fractionated into five fractions using an ultrafiltration with different molecular-weight cut-offs. The order of the molecular weights of the five fractions calculated from the HPSEC analysis corresponded to that defined by ultrafiltration. This supported the reliability of the method.

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