VARIABLES AFFECTING THE SUPERCRITICAL FLUID EXTRACTION OF ANALYTES FROM OCTADECYLSILANE SOLID-PHASE SORBENTS

The relative effects of the numerous variables which can influence the supercritical fluid extraction (SFE) efficiencies of analytes from solid-phase extraction (SPE) sorbents is discussed. SFE efficiencies are not only influenced by experimental variables such as temperature and pressure (density), but also by sample/matrix variables, extraction vessel variables and collection variables. The significance of many of these variables are underrated, and studies aimed at quantitative comparisons of these variables have generally focused on extraction of analytes from endogenous matrices, rather than SPE sorbents such as those evaluated here. The relative effects of temperature and density have been quantitatively compared for the extraction of polycyclic aromatic hydrocarbons and methoxychlor from octadecylsilane sorbents. Under the conditions studied, the effect of temperature was found to be of equal importance to that of density, and either could be used to vary the recovery of analytes over an extremely wide range. A more thorough knowledge of the relative effects of all of the controllable variables should facilitate optimization of SFE of analytes from SPE sorbents for maximum selectivity as well as maximum overall recoveries.