Characterization of flow and voltage profiles in planar electrochromatography

Abstract

Planar electrochromatography (PEC) is a new technology for thin layer chromatography (TLC) where the separation is driven by electroosmotic forces, not capillary action. This allows for much faster and more efficient chromatography in a planar format. Care needs to be taken when performing these experiments because voltage and flow characteristics can change through a single run, due to buffer gradients, temperature changes (Joule heating) and localized plate heterogeneity. We have designed a PEC instrument and cover grid to allow investigation of flow and voltage characteristics as solvent moves across a TLC plate. Our unique cover grid allows monitoring voltage at eight discrete points between the positive and negative reservoirs. A linear relationship between voltage and distance should be seen, giving a constant voltage drop across a plate, but this did not occur. This non-linear function changes over time, following the plate equilibration. Once a plate is equilibrated, voltage and flow characteristics remain fairly constant. Theoretical calculations support the physical observations. Larger plate widths (5 cm) were also briefly investigated and it is concluded that large width plates could be easily implemented to maintain multiple sample capability.