High-Speed Capillary Electrophoresis Using a Thin-Wall Fused-Silica Capillary Combined with Backscatter...

High-speed capillary electrophoresis (HSCE) is implemented using a 10 cm total length fused-silica capillary (50 μm i.d., 80 μm o.d.) combined with refractive index (RI) detection using backscatter interferometry (BSI). The short capillary length reduces analysis time while the ultrathin wall (15 μm) efficiently dissipates heat from the separation channel, mitigating the deleterious effects of Joule heating. The separation capillary is mounted on a temperature-controlled heat sink that stabilizes the temperature to ±0.004 °C. This temperature stabilization improves separation efficiency and enhances RI detection. Ohm's Law plots confirm the superior heat dissipation of the HSCE capillary compared to a similarly prepared conventional CE capillary (50 μm i.d., 363 μm o.d.). The speed and efficiency of HSCE combined with universal RI detection is illustrated through the separation of K⁺, Ba²⁺, Mg²⁺, Na⁺, Li⁺, and Tris⁺ in approximately 30 s, with efficiencies greater than 500 000 plates/m. Run-to-run repeatability is explored using nine consecutive electrokinetic injections of a K⁺, Na⁺, and Li⁺ mixture. The average migration times and %RSD for K⁺, Na⁺, and Li⁺ were measured to be 22.04 s (1.59%), 26.81 s (1.38%), and 29.80 s (2.21%), respectively. Finally, we show that the BSI signal is sensitive to the separation voltage through the Kerr mechanism. This leads to peaks in the electropherogram from the injection process that are useful for precisely defining the start of each separation and quantifying the amount of sample injected onto the capillary.