Large-volume sample sweeping with a high theoretical plate number using a coupled-capillary in capillary electrophoresis

A large-volume sample injection (> 5 μL) with an extremely high theoretical plate number (N > 10⁷) was achieved when the sweeping-MEKC mode and a coupled-capillary (100 - 50 μm i.d.) were simultaneously used in a capillary electrophoresis (CE) separation. A low-cost and compact violet-LED (∼2 mW) was used as the fluorescence excitation source. As a result, the theoretical plate numbers of the detected peaks (two model compounds: naphthalene-2,3-dicarboxaldehyde derivatized-dopamine and -norepinephrine) were 1.0 × 10⁷ and 7.4 × 10⁶, respectively. The limits of detection (at S/N = 3) of these were determined to be 2.8 × 10^-10 M (92 ppt) and 2.3 × 10^-10 M (83 ppt), respectively. 2006