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 d etection, combined with flow injection (FI) sample introduction, was constr ucted 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 sys tems. End-column amperometric detection was accomplished with separation vo ltage decoupled from the detection system, employing a microdisk working el ectrode positioned immediately outside the capillary outlet in the other si de-arm, which functioned as a large-volume reservoir. Sample dispersion in the FI system and the FI-CE interface was minimized by intercalating the sa mple zone between two air segments. Performance of the FI-CE amperometric s ystem was demonstrated by separation of sugars. Separation of sucrose and g lucose was performed with a 5 cm, 25 mu m i.d. capillary with 1.7 kV separa tion 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 fo r glucose. Peak height precisions were 2.1 and 2.4% R.S.D. (n = 9) for sucr ose and glucose, respectively. (C) 2000 Elsevier Science B.V. All rights re served.