Fundamental and practical aspects of solid-phase and supercritical fluid extraction.

摘要

The kinetic and retention properties of a silica based octadecylsiloxane-bonded silica sorbent used in solid-phase extraction (SPE) were determined by high pressure liquid chromatography (HPLC). The sorbent had a high bonded phase density resulting in a material with very low intraparticle porosity and favorable retention and mass transfer properties. Typical SPE cartridges were found to have a low and variable packing density which causes poor sampling performance and reproducibility. Abraham's Solvation Parameter Model was used to relate the retention factor to the characteristic properties of the chromatographic system and to estimate breakthrough volumes. All parameters required to predict the optimum sampling conditions, breakthrough volume, and recovery in SPE were conveniently obtained by HPLC.;Solvent-assisted supercritical fluid extraction (SFE) was found to be superior to Soxhlet extraction, solvent extraction at reflux, and simultaneous steam distillation/solvent extraction for the isolation of semivolatile compounds, including 2-hydroxycinnamaldehyde, from the cinnamons of commerce. Solvent trapping, cryogenic solventless trapping, and solid-phase sorbent trapping were studied to determine the optimum technique for collecting the semivolatile components from powdered cinnamon bark after solvent-assisted SFE. Principal component analysis and cluster analysis using the relative composition of twelve major semivolatile compounds provided a clear distinction between true cinnamon and cassia.;Solid-phase microextraction (SPME) was compared to solvent-assisted SFE for the isolation of semivolatile compounds from the cinnamons of commerce. SPME proved to be a quicker and more sensitive way to characterize powdered cinnamon than previous methods however quantitation of components was difficult due to sample matrix effects.;Silica gel thin layer chromatography (TLC) using automated multiple development after solvent-assisted SFE was used to screen Aloe leaf products for Aloin and aloe-emodien. The method was found to be useful for the screening of Aloe products for human consumption.