Separation and Identification of Higher Fullerenes by High-Performance Liquid Chromatography Coupled with Electrospray Ionization Mass Spectrometry

The separation and identification of higher fullerenes extracted from carbon soot were studied using high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS). The mixture of fullerenes extracted from carbon soot was first separated by a preparative-scale column packed with monomeric octadecylsilica (ODS), which mainly controls the elution order of fullerenes by their relative molecular mass. Then five batches of the fraction which should contain higher fullerenes larger than C₈₄ were collected and subsequently concentrated, followed by analytical-scale separation with a polymeric ODS column, which can elute fullerenes according to their shape and structure. Therefore, this stationary phase can separate many isomers of higher fullerenes. By identification using LC-ESI-MS, the existence of several higher fullerenes up to C₉₈ and their isomers were confirmed. Temperature effects in the separation of fullerenes were also examined and the results indicated that separation of C₈₂ and C₈₄ isomers could be achieved at a column temperature lower than 15°C using a polymeric ODS column.