OPTIMIZATION OF SUPERCRITICAL FLUID EXTRACTION OF ENVIRONMENTAL-POLLUTANTS FROM A LIQUID SOLID EXTRACTION CARTRIDGE

Experimental design techniques are used to optimize the conditions of supercritical fluid extraction (SFE) of 29 compounds, including polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides from a liquid-solid extraction cartridge. These compounds are representative of larger classes of compounds of environmental concern. A statistical 23factorial experimental design is initially performed to study the relative importance of three SFE variables: pressure, temperature, and extraction time. The pressure has a statistically significant effect on the recovery of all compounds studied. The next most influential variable is length of extraction time, which has a statistically significant effect on the recovery of some of the PAHs. The temperature is the least influential factor. Following the factorial design, a variable-size simplex optimization is used to demonstrate that the SFE conditions can be optimized to obtain the best overall recoveries of the compounds studied. For those analytes demonstrating low recoveries in pure supercritical carbon dioxide (CO2), a methanol modifier is added to improve recoveries. By adding an appropriate amount of methanol into the cartridge, those analytes can be quantitatively recovered. © 1992 Oxford University Press.