TRAPPING EFFICIENCIES OF VARIOUS ADSORBENTS IN SUPERCRITICAL-FLUID EXTRACTION WITH MODIFIED CARBON-DIOXIDE

One way of collecting extracted analytes after a supercritical fluid e xtraction (SFE) is to pass the depressurized fluid through a trap comp osed of a solid adsorbent. The influence of the adsorbent nature on th e trap efficiency has been studied. First, the retention factors of ea ch compound of a polarity test mix (tetracosane, naphthalene, fluorant hene, acetophenone, N,N-dimethylaniline, 2-naphthol, decanoic acid) ha ve been determined on five high specific area (greater than 800 m(2)/g ) polymeric phases by supercritical fluid chromatography (SFC), The co mparison of this values with those obtained on octadecyl silica (ODS) showed that polymeric phases have the greatest retention power. After that, the efficiency of a solid trap filled with the greatest retentio n power polymeric adsorbent was evaluated by using pure carbon dioxide and 2.5%, 5%, 10%, and 20% methanol-modified carbon dioxide. As expec ted, this trap permitted a quantitative collection of all the former c ompounds even when a content as high as 10% of methanol was implemente d. A solid trap filled with ODS adsorbent allowed quantitative collect ion of all the compounds only at a methanol content lower than 2.5%.