Capillary electrophoresis system with flow injection sample introduction and chemiluminescence detection on a chip platform

Abstract

A capillary electrophoresis (CE) system with chemiluminescence (CL) detection was combined with flow injection (FI) sample introduction on a chip platform. A falling-drop interface was applied to perform FI split-flow sample introduction while achieving electrical isolation from the CE high voltage. A tubular reservoir at the capillary outlet served as both the CL reaction and detection cell for the luminol–peroxide–metallic ion chemiluminescent reaction, with the luminol included in the separation buffer and CL reagent H₂O₂ continuously introduced into the outlet reservoir. An optical fiber was positioned within the outlet reservoir directly opposite, and 300 µm away from, the capillary outlet for collecting and transferring the generated CL to the PMT. The peak height signals and the separation efficiency were almost independent of the reagent flow-rate, making the system a robust one. The performance of the system was illustrated by the separation of Co(II) and Cu(II), achieving baseline separation in 60 s. Detection limits (3σ) were 1.25 × 10⁻⁸ and 2.3 × 10⁻⁶ mol dm⁻³ for Co(II) and Cu(II), respectively. Peak height precision was 1.9% RSD (n=9) at the 10⁻⁷ mol dm⁻³ Co level.