Combination of flow injection with capillary electrophoresis - Part 7. Microchip capillary electrophoresis system with flow injection sample introduction and amperometric detection

A microchip-based capillary electrophoresis (CE) system with amperometric detection, combined with flow injection (FI) sample introduction, was constructed from components readily available in the analytical laboratory. An H-channel configuration was used with separation capillary positioned between two tubular side-arms, and a falling-drop interface connected to one side-arm was developed to achieve electrical isolation between the FI and CE systems. End-column amperometric detection was accomplished with separation voltage decoupled from the detection system, employing a microdisk working electrode positioned immediately outside the capillary outlet in the other side-arm, which functioned as a large-volume reservoir. Sample dispersion in the FI system and the FI-CE interface was minimized by intercalating the sample zone between two air segments. Performance of the FI-CE amperometric system was demonstrated by separation of sugars. Separation of sucrose and glucose was performed with a 5 cm, 25 mu m i.d. capillary with 1.7 kV separation voltage in about 60 s (40 mu m plate height for glucose), achieving a sampling frequency of over 65 h(-1). Responses for sucrose and glucose were linear in the range of 10-1000 mu M with sensitivities of 0.011 and 0.025 nA mu M-1. Detection limits (S/N = 3) were 2 mu M for sucrose and 1 mu M for glucose. Peak height precisions were 2.1 and 2.4% R.S.D. (n = 9) for sucrose and glucose, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.