Improved extraction of metallofullerenes with DMF at high temperature

Gd, Th, Y, Sm-metallofullerenes were extracted with DMF by high-temperature extraction or by Soxhlet extraction. The extractable residues were then dissolved in toluene for further HPLC separation, respectively, Comparison of the mass spectra and HPLC chromatograms of the toluene solutions from the two extraction methods indicated that the one-step high-temperature-DMF extraction was more effective and convenient. By using the high-temperature-DMF method. the extraction efficiency of Gd@C-82 was 15 times higher than that by Soxhlet extraction. The studies of other Gd-monometallofullerenes, Gd-dimetallofullerenes and Tb, Y, Sm-metallofullerenes gave similar results. Some possible reasons are proposed. (C) 2002 Elsevier Science Ltd. All rights reserved.