Construction, evaluation and analytical operation of a modular capillary electrophoresis instrument

Summary

A self-designed capillary electrophoresis instrument is described in detail. It has been constructed in a modular mode for systematical studies on CE and related techniques. The instrument is characterized by the following features:

• -alternative modes of automated sample introduction,

• -liquid cooling and adequate temperature control of the separation capillary,

• -computer controlled adjustment of voltage and voltage gradients,

• -automated aquisition, handling and evaluation of analytical data.

The reproducibility of data which characterize the performance of the instrumentation (“efficiency”, migration times) has been investigated by a large number of repetitive measurements. Quantitative data such as absolute and relative peak areas have also been measured and evaluated. The results of these investigations show that the apparatus is well suited for reproducible measurements. The influence of significant parameters such as temperature, buffer pH or the concentration of organic modifier in the buffer on the separation performance were studied. A particular kind of peak tailing which may arise due to poor sample introduction can be avoided by inclusion of a rinsing step of the outside of the capillary inlet. The rinsing is achieved by dipping the column inlet into another vial with buffer before the actual separation is initiated. A four step procedure of sample introduction is proposed. Typical capillary electrophoretic separations are shown.