SUPERCRITICAL-FLUID EXTRACTION OF ENVIRONMENTAL ANALYTES USING TRIFLUOROMETHANE

Trifluoromethane (CHF3) was evaluated as a supercritical fluid extractant. The large dipole moment and easily accessed critical temperature and pressure of CHF3make it a candidate for extracting polar and thermally labile compounds. Sulfonyl urea herbicides and polycyclic aromatic hydrocarbons (PAHs) were used as probes to determine the extraction ability of CHF3in comparison with other commonly used supercritical fluids such as carbon dioxide (CO2), methanol-modified CO2and chlorodifluoromethane (CHCIF2). A 30% increase in extraction efficiency of the sulfonyl urea herbicides was obtained when CHF3 was used as the extraction solvent rather than CO2; the quantitative recovery (more than 90%) of these analytes was achieved only by the use of 2% methanol-modifier in the CO2extractant. The extraction behavior of some moderately polar three- and four-ring PAHs from sodium montmorillonite clay was also studied using CHF3CHCIF2and CO2Under equivalent extraction conditions, recoveries for the PAHs ranked CHCIF2b CO2b CHF3Results with CHCIF2matched those obtained by Soxhlet extraction. © Oxford University Press 1992.