Capillary zone electrophoretic separation of carbon microparticles

Abstract

Capillary zone electrophoretic separations of carbon particles in micrometer and submicrometer sizes were achieved in an aqueous 10 mM sodium tetraborate solution containing 10％(ｗ/v) polyethylene glycol 400 at pH 9.2 as background electrolyte solution(BGE). Since migration time of the carbon particle increased with increasing its size, it was shown that the larger size of the carbon particle had a more negatively electric charge. EIectropherograms corresponded to histograms of size distributions from images observed by scanning electron microscope (SEM) or a digital microscope. The size distribution could be measured within 20 min by capillary electrophoresis (CE). This means that the generally well-used SEM could be replaced by CE for measurements of size distributions for the carbon particles in micrometer and submicrometer, because the CE measurement could be easier than SEM at a shorter time Also, a surface density of electric charge for a graphitic carbon microparticle of a 3.6 μm diameter was obtained from electrophoretic mobility measured by CE. It was -1.1 × 10(exp -5) C m(exp -2) at 30 C. Since this value would depend on numbers of proton-dissociating carboxyl and phenol groups on the carbon microparticle in BGE, it could be used as an index to estimate oxidized carbons on the surface of carbon microparticles.