Development of evaporative light scattering detector for capillary electrochromatography and capillary liquid...

The paper describes a microfluidic evaporative light scattering detector (μELSD) for capillary electrochromatography and capillary liquid chromatography. The detector, consisting of a microfluidic nebulizer, a miniaturized evaporative module, a sheath gas module, and a light scattering chamber, was developed and optimized. Carrier gas exits from an extremely narrow circular gap (about 5 μm) between the spraying capillary o.d. and the nozzle i.d., impacting on the mobile phase liquid with supersonic velocity, to nebulize the effluent of a few hundred nL/min from the capillary outlet. The evaporation process was found to be accomplished at ambient temperature. A sheath gas module featuring a structural necking subsequent to drift tube endings was found to enhance the reproducibility and increase the S/N. Excellent linearity of the optimal μELSD was 3 orders of magnitude (0.2-40 ng; R(2) = 0.9998). The limit of detection (LOD) for glucose with a capillary column was 100 pg. Finally, the μELSD coupled to pressurized capillary eletrochromatography (pCEC) was applied to the analysis of six active components in traditional Chinese medicine extract, demonstrating the feasibility of the detector for capillary liquid separation system.