Panaceas and pitfalls in electrodriven chromatographic techniques

[摘要] In this thesis the main capillary electrodriven chromatographic techniques (i.e.Capillary Electrochromatography CEC, Micellar Electrokinetic ChromatographyMEKC and Microemulsion Electrokinetic Chromatography MEEKC) were comparedin terms of column manufacturing, fundamental chromatographic performance,and some applications were developed. The first stage of this thesis aimed atdeveloping improved packed and open tubular CEC columns. For themanufacturing of packed CEC columns, the frit-burning step proved of criticalimportance, together with the slow build-up of the packed bed. The making ofopen tubular columns is a relatively simple, one pot sol-gel reaction takingplace in mild conditions. The nature of the gel and the resulting selectivity of thecolumn could easily be changed by changing the precursors.In a second stage of this thesis the packed and open tubular CEC columns wereevaluated chromatographically and compared with the results obtained by MEKCand MEEKC. All electrodriven separation techniques showed high efficiencies. Theselectivity proved easier to tune with sol-gel chemistry for the making of opentubular columns. Resolution is acceptable for packed CEC, MEKC and MEEKC. Forpeak capacity, CEC has the advantage of a practically non-limited elution time,while MEKC and MEEKC suffer of the drawback of the existence of an elutionwindow which is limited in time by the elution of the micelles.Some applications were developed in this study on open tubular CEC columnsand for the packed CEC columns. Various sugars derivatized with 9-aminopyrene-1,4,6-trisulfonic acid (APTS) could be separated with open tubularCEC, using an octyl, amino or cyano stationary phase. Open tubular columnscontaining α, β and γ cyclodextrins attached to the stationary phase weredeveloped. This approach proved promising for the separation of positionalisomers. A method was developed for the analyses of a mixture of carbamatesand for several steroids with packed column CEC directly coupled with MS.

[发布机构] Stellenbosch University