DEVELOPMENT OF A FLEXIBLE, ONLINE SUPERCRITICAL FLUID EXTRACTION GAS-CHROMATOGRAPHIC (SFE-GC) SYSTEM

An on-line supercritical fluid extraction-gas chromatography (SFE-GC) interface is described and studied both with and without an intermediate Tenax-GC adsorption step. The utility of this secondary adsorption step and its affect on interface performance are the main objectives of this work. Semivolatile pesticides, herbicides, and polychlorinated biphenyls are used as test analytes. The addition of the Tenax-GC adsorption step allows for larger supercritical fluid extraction volumes than are possible using a direct SFE-GC interface. This approach can thus provide for greater flexibility in selecting extraction volume, extraction time, and sample volume. The use of the new interface should also permit on-line SFE-GC analyses using methanol-modified CO2 as the extraction fluid. The intermediate trapping step also improves the chromatographic efficiency relative to direct SFE-GC. Replicate analyses generally indicate less than 5% relative standard deviation for peak areas. The extraction and analysis of compounds present at less than 100 ppb should be possible from a clean matrix using sample sizes of several milliliters.