CORRELATION BETWEEN ZONE VELOCITY AND CURRENT IN AUTOMATED SINGLE CAPILLARY ISOTACHOPHORESIS-ZONE ELECTROPHORESIS

In single capillary isotachophoresis-zone electrophoresis (ITP-CZE) th e sample zone velocity is varying with its position in the capillary d uring the focusing step. When the voltage is kept constant, the curren t changes to the same extent. Correlation between the current and the sample zone velocity can therefore be used to calculate the velocity o f the hydrodynamic flow that is needed to counterbalance the sample zo ne velocity. Measured data are in agreement with calculations implying that current monitoring can be used in an automated feedback system t o regulate the hydrodynamic flow velocity during the focusing step. Co nditions are described where automated anionic single capillary ITP-CZ E can be performed without application of a hydrodynamic counterflow, extending its applicability to any commercially available CZE system. Correlation between the ITP current and the sample zone position in th e capillary was used to determine the moment for automatic switching f rom ITP to CZE. The reproducibility of the corresponding CZE migration times is investigated in addition to the effect of the remaining ITP terminator zone length on the CZE separation. A remaining terminator z one length of 10% of the total capillary length still resulted in an a cceptable CZE performance.