Improving the Use of CE in a Chromatographer's World

Since the introduction of commercial capillary electrophoresis (CE) systems over 10 years ago, separation mechanisms have become more clearly understood, and can now be modelled, simulated and thus controlled. However, it is important to think in terms of the “CE world” when troubleshooting CE methods rather than using conventional “chromatography-mode thinking”. Raw electrophoretic data transformation into the effective mobility scale is a first step towards better reproducibility for both qualitative and quantitative analyses. Application examples are used to illustrate the power of this data transformation tool.

Introduction :
“CE-mode thinking”, as termed by Whatley (1), is a prerequisite for handling capillary electrophoresis (CE) problems and obtaining robust results. Acquiring good reproducibility in migration times (qualitative aspects) and peak integration (quantitative aspects) forms part of this goal. Low reproducibility associated with these parameters is often related to small changes in endoosmotic flow (EOF) resulting from uncontrollable alterations in the capillary surface, which in turn leads to migration time shifts, especially when analysing real samples (matrix effects). A first step towards increasing qualitative and quantitative precision is to choose and standardize the operating, calibrating and equilibrating conditions. This will lead to stable EOF and reproducible migration times, and can be achieved with different experimental set-ups, such as adequate rinse steps or voltage preconditioning techniques (2).

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