Submitted to: Intl Symposium on Supercritical Fluid Chromatography and Extraction
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/1998
Publication Date: N/A
Technical Abstract: Pesticide sorption coefficients (Kd) have been most commonly determined using batch slurry, column, or centrifugation techniques. These techniques suffer from a number of drawbacks. For instance, they require soils with water contents above field capacity so that soil and soil solution can be separated before analysis. The experiments are usually carried out after drying the soils and water content is expected to have a great influence o pesticide sorption. Also, the extraction procedure usually alters the physical and chemical characteristics of the soil, resulting changes in properties of the binding sites during the experiment. Therefore, techniques are needed where Kd can be determined in field-moist soils. The selectivity of SFE has recently been used to extract atrazine and sulfonylurea herbicides from soil solution without also extracting residues bound to the soil particles. The objective of this study was to further investigate the SFE technique and determine linuron sorption in field-mois soils. Experiments were performed using low density (i.e. 0.25 g/mL) supercritical carbon dioxide to remove linuron from the water phase only, thus allowing calculation of sorption coefficients at low water contents. Kd values for soil at 12 percent moisture content was about 10 mL/g for a sandy soil and 20 for a clay soil. The higher Kd on the clay is presumably due its higher organic carbon content. Influence of SFE temperature and moisture content on sorption behavior will be studied further.