Application of a Rule to Illustration of Electrophoretic Results and Standarization of Electrophoresis Apparatus

An apparatus for continuous registration of the electric field within an electrophoretic column was developed. It comprises a rectangular separation trough with an ordered array of 256 electrodes over a length of 10 em and perpendicular to the current flow. Electrodes are photoetched on a supporting glass plate from a vapor deposited thin layer of Sno 2 semiconductor (width: 6011m, height: O.lllm, space between: 34011m). The rectangular trough is defined by a gasket between the glass plate and a block of plexiglass. This block contains the sample inlet system and the connections to the electrode compartments. A power supply, appropriate detection electronics and fluid handling devices complete the apparatus. The electrode array is scanned mechanically by two graphite brushes, controlled by a microprocessor. The measured potential gradient between adjacent electrodes is recorded and stored in the computer memory of a Heathkit H8 computer, which handles all control functions, data treatment and printout of results, Measuring data of each detection channel nearly simultaneously enables us to follow the dynamics of electrophoretic processes. This allows the automation of an isotachophoretic analysis by following the vanishing of mixed zones ~syrnptotic approach of the steady state}. The device is a useful tool for validation studies of computer modeling in electrophoresis. Examples showing the electrophoretic evolution in each of the four classical modes ~BE, ZE, ITP and IEF} as well as in combinations are given. Results are compared with theoretical predictions. Various isotachophoretic applications are presented to demonstrate the usefulness of this new device in instrumental analysis.