Solution properties of C-60 and C-70 fullerenes and C-21 to C-40 n-alkanesat infinite dilution in carbon dioxide from supercritical fluid chromatography

Retention factors of eleven heavy n-alkanes (C21H44, C22H46, C23H48, C24H50 , C25H52, C27H56, C28H58, C31H64, C34H70 C36H74, and C40H82) and C-60 and C -70 fullerenes were measured within 311-431 K and 8.7-39 MPa by supercritic al fluid chromatography in an open tubular capillary column. This data set was obtained using a poly(methyl-n-octyl siloxane) stationary polymer and c arbon dioxide as the mobile-phase fluid. The retention factors are employed to derive the partial molar volumes of the solutes at infinite dilution in CO2 and the infinite-dilution molar enthalpies of transfer of the solutes from the stationary phase to supercritical CO2. The partial molar volumes a re subsequently transformed to quantities characterizing short-range solute -CO2 interactions, and the effects are shown of the corrections for dissolu tion Of CO2 in the stationary polymer on these quantities. Distinct differe nces between the n-alkane-CO2 and the fullerene-CO2 interactions have been found and discussed. Overall, the resultant partial molar properties sugges t that the fullerene-CO2 interactions are less attractive than the n-alkane -CO2 interactions.