Supercritical Fluid Extraction and Chromatography of Representative Agricultural Products with Capillary and Microbore Columns

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Abstract
The effects of varying density and temperature of the supercritical mobile phase in extracting representative agricultural products from soil matrices are examined. Results obtained by using pure and modified carbon dioxide supercritical fluids are compared. Extraction parameters are optimized to allow quantitative extraction of 14C radiolabeled compounds from soil matrices. After supercritical fluid extraction (SFE) is optimized, the extraction apparatus is coupled with supercritical fluid chromatography (SFC). Extracted components are then examined on-line. Modified carbon dioxide mobile phases are used during extraction, while pure carbon dioxide is used as the chromatographic mobile phase. The carbon dioxide is modified by adding microliter quantities of polar solvents directly to the sample matrix in the extraction vessel. In this way, flame ionization can be used for chromatographic detection; the extraction modifier elutes as a solvent front in the chromatogram. Both capillary and microbore columns are investigated for chromatographic analysis. Lower detection limits are obtained with the microbore columns and larger sample loops. A correlation between chromatographic capacity factor and extractability is demonstrated.