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Abstract: HPLC microchips are investigated experimentally with respect to packing density, pressure drop–flow rate relation, hydraulic permeability, and separation efficiency. The prototype microchips provide minimal dead volume, on-chip UV detection, and a 75mm long separation channel with a ca. 50μm×75μm trapezoidal cross-section. A custom-built stainless-steel holder allowed to adopt optimized packing conditions. Separation channels were slurry-packed with 3, 5, and 10μm-sized spherical, porous C8-silica particles. Differences in interparticle porosity, permeability, and plate height data are analyzed and consistently explained by different microchannel-to-particle size (particle-aspect) ratios and particle size distributions. [Copyright &y& Elsevier]

The article focuses on the application of high-pressure liquid chromatography (LC) in lab-on-a-chip devices. The use of high-pressure LC in lab-on-a-chip devices calls for the integration of various operations, such as band broadening, gradient elution and packing microstructure. The article discusses the advantages of miniaturization of high-pressure liquid chromatography. The author concludes that high-pressure LC microchip can be a powerful tool than nano-LC.

This work investigates the impact of conduit geometry on the chromatographic performance of typical particulate microchip packings. For this purpose, high-performance liquid chromatography (HPLC)/UV-microchips with separation channels of quadratic, trapezoidal, or Gaussian cross section were fabricated by direct laser ablation and lamination of multiple polyimide layers and then slurry- packed with either 3 or 5 μm spherical porous C8-silica particles under optimized packing conditions. Experimentally determined plate height curves for the empty microchannels are compared with dispersion coefficients from theoretical calculations. Packing densities and plate height curves for the various microchip packings are presented and conclusively explained. The 3 μm packings display a high packing density irrespective of their conduit geometries, and their performance reflects the dispersion behavior of the empty channels. Dispersion in 5 μm packings correlates with the achieved packing densities, which are limited by the number and accessibility of corners in a given conduit shape. [ABSTRACT FROM AUTHOR]