Analytical Sciences

Large-Volume Sample Sweeping with a High Theoretical Plate Number Using a Coupled-Capillary in Capillary Electrophoresis

Yen-Sheng CHANG, Chun-Min SHIH, Yen-Cheng LI, and Cheng-Huang LIN

Department of Chemistry, National Taiwan Normal University, 88 Sec. 4, Tingchow Road, Taipei, Taiwan

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.

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