Application of high-performance size-exclusion liquid chromatography to the study of copper speciation in waters extracted from sewage sludge treated soils

Abstract

A simple linear relationship has been established between the ionic strength and electrical conductivity of soil solutions. This relationship allows the preparation of an eluent for high-performance liquid chromatography which resembles the soil solution in terms of pH and ionic strength without requiring a complete ionic analysis of the sample. High-performance size-exclusion chromatography has been used in conjunction with ultraviolet detection for the molecular species and graphite furnace atomic absorption spectrometry for copper. A TSK G3000 SW column was used with an eluent consisting of Na₂HPO₄-NaH₂PO₄. The analysis of soil solutions extracted by centrifugation using this system enabled the separation of the soluble organic matter into fractions of high and low relative molecular mass. The determination of copper in these fractions revealed that 60–80% of the copper is bound to humic and fulvic acids and is unavailable for plant uptake. The proportion of copper complexed with organic matter of high relative molecular mass was found to be affected by the drainage status of the soil.