Hydrodynamic sample injection into short electrophoretic capillary in systems with a flow-gating interface

•On-line connection of CE separation with sampling by the microdialysis probe.•Flow-gating interface for hydrodynamic sample injection into short electrophoretic capillary.•On-line monitoring of chemical and biochemical processes.•Fully automatic apparatus for sequence analysis.•Fast electrophoretic separation with universal contactless conductivity detection.

An electrophoretic apparatus with a flow-gating interface has been developed, enabling hydrodynamic sequence injection of the sample into the separation capillary from the liquid flow by underpressure generated in the outlet electrophoretic vessel. The properties of the apparatus were tested on an artificial sample of an equimolar mixture of 100 μM potassium and sodium ions and arginine. The repeatability of the injection of the tested ions expressed as RSD (in%) for the peak area, peak height and migration time was in the range 0.76-2.08, 0.18-0.68 and 0.28-0.48, respectively. Under optimum conditions, the apparatus was used for sequence monitoring of the reaction between the antidiabetic drug phenyl biguanide and the glycation agent methyl glyoxal. The reaction solution was continuously sampled by a microdialysis probe from a thermostated external vessel using a syringe pump at a flow rate of 3 μL min−1 and was injected into a separation capillary at certain time intervals. The electrophoretic separation progressed in a capillary with an internal diameter of 50 μm with a length of 11.5 cm and was monitored using a contactless conductivity detector.