Separations of alkyl‐substituted anthracenes using cyclodextrin distribution capillary electrochromatography

Alkyl-substituted anthracenes were separated using a technique dubbed cyclodextrin distribution capillary electrochromatography (CDCE). Native β- or γ-cyclodextrins (CDs), in conjunction with carboxymethyl-β-cyclodextrin (CM-β-CD) or sulfated-βcyclodextrin (Su-β-CD), were employed in running buffers to create a dual-CD-phase system. In this system, analytes are separated based upon their differential distribution between the neutral CDs (β-CD or γ-CD) moving with the bulk electroosmotic flow and electrophoretically mediated, charged CDs (CM-β-CD or Su-β-CD). Comparisons are drawn between CDCE and CD-modified micellar electrokinetic capillary chromatography. CDCE is shown to provide unique selectivity and good resolution of methyl-ethyl-substituted anthracenes. Control of retention is possible through varying the concentrations and types of CDs employed. Laser-induced fluorescence provides detection limits in the low-to-subparts per billion range. Field strength and total CD concentration exert a substantial influence on the observed plate height. Analysis of CM-β-CD with capillary electrophoresis reveals information about composition (range of degree of substitution) of the derivatized CD phase. Molecular modeling is also employed to investigate that position of CM substitution has on the shape of the CD.