Separation of Fullerenes C60, C70, and C76-84 on Polystyrene Divinylbenzene Columns

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Abstract
New HPLC methods have been developed to effectively separate and recover essentially pure amounts of C60 and C70 fullerenes from the lower MW contaminants and higher MW fullerenes co-extracted from carbon soot. Separation with toluene/methylene chloride mobile phase results from different degrees of interaction of conjugated π-electrons of the fullerenes and the polystyrene divinylbenzene (PSDVB) resin stationary phase. The presence of either toluene or CS2 in the mobile phase attenuates π-electron interactions. The separation mechanism becomes predominantly size exclusion chromatography for a CS2 concentration in the mobile phase ≥ 60%. Excellent separation of C60, C70 and C76–84 is obtained with the analytical Envirosep-ABC(tm) columns in less than 15 minutes. Substituted fullerene reaction products are also well separated from their parent compounds. The effects of column size and PSDVB pore size on analytical separation, along with the effects of pore size, mobile phase, and sample size on semi-preparative separation of C60 and C70 are reported. Semi-preparative columns can process with satisfactory resolution more than 14.5 mg of fullerenes per run using methylene chloride:toluene as mobile phase. These studies led to the development of an optimized set of columns consisting of a guard column (60×21.2 mm) and a modified preparative column (350×21.2 mm) with improved flow design and separation efficiency.