AMPEROMETRIC AND FAST SCAN-RATE CYCLIC VOLTAMMETRY DETECTION AT A MICROELECTRODE FOR GEL-PERMEATION HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY OF FULLERENES

Amperometry and fast scan-rate cyclic voltammetry (CV) at a 10-mum-diameter platinum microelectrode were utilized for detection and in situ identification of fullerenes which were separated by gel permeation high-performance liquid chromatography. The microelectrode and inlet capillary nozzle were arranged perpendicularly. The limiting currents were virtually independent of the mobile phase flow rate in the range 0.1-2.0 mL min-1 for a distance between the microelectrode and inlet capillary nozzle less-than-or-equal-to 0.10 mm. A toluene extract of the laser-vaporized soot containing low molecular mass fullerenes was resolved on two gel permeation columns which were connected in series. The mobile phase was dichloromethane/cyclohexane, 90/10 (v/v), 0.01 M tetra-n-butylammonium perchlorate. C60 and C70 were the major components of the extract and were present in a 3:1 mass ratio. Other higher fullerenes were also present In lower concentration. The number and shapes of the peaks in chromatograms obtained with amperometric detection at -1.3 V vs SCE were the same as those obtained with UV-visible spectroscopic detection at 365 nm, thus indicating that all of the detected compounds both absorb UV-visible light and are electrochemically active. Extracolumn peak broadenings due to detection and detectability (83.8 ng for C60) were also the same in both detection techniques. In situ fast scan-rate voltammograms of C60 and C70 were obtained during elution, and the reversible E1/2 values of the third and fourth electroreductions could be used for their identification.