Automated instrumentation for comprehensive isotachophoresis-capillary zone electrophoresis

An automated comprehensive isotachophoresis - capillary zone electrophoresis (ITP-CZE) system is described. The sample is focused in the first capillary by ITP and injected repeatedly into the second smaller diameter capillary for more rapid CZE separation. Since only small portions of the concentrated zones are sequentially injected for CZE separation, overloading was not observed. Moreover, the sensitivity is enhanced because all of the concentrated zones are analyzed and the results are summed. A single detector (only for the CZE dimension) is required, and accurate timing for CZE injection is not necessary. The system was evaluated using a mixture of angiotensins. The effect of addition of leading electrolyte at the junction of the ITP and CZE capillaries before each CZE run on comprehensive ITP-CZE peak area was studied, and leading electrolyte volumes between 7 and 11 mu L led to the best sensitivity. Under optimized conditions, a detection limit of approximately 5 nM could be achieved by injecting 10 mu L of angiotensin solution.