REPRESENTING ISOCRATIC MULTICOMPONENT SOLID-PHASE EXTRACTION DATA BY AN EXTENSION OF LIQUID-LIQUID-EXTRACTION THEORY

The theory and a model of representation for isocratic multicomponent solid-phase extraction (SPE) data are presented. The model requires the determination of extraction recovery as a function of extractant volume. The recovery/extractant volume data are then analyzed to determine whether further wash optimization studies might be promising or if another SPE stationary phase should be chosen. Similarly extracted species are represented in a consistent manner, allowing systematic variation of the wash solvent composition to optimize selectivity, Extraction of a mixture of allkyldimethylbenzylammonium chloride is performed, and analysis of the resulting data is seen to be consistent with extraction of a homologous series. A complex mixture of epipodophyllotoxin-related compounds is analyzed by the model presented, and selective wash conditions are developed. The effect of mass and volume on SPE column loading is demonstrated by extraction of a series of p-hydroxybenzoic acid ester compounds. The model allows inference of the selectivity, extent of irreversibly bound analyte, loading, and type of elution profile.