Repetitive injection method: A tool for investigation of injection zone formation and its compression in microfluidic liquid chromatography

Improving the Sensitivity, Resolution, and Peak Capacity of Gradient Elution in Capillary Liquid Chromatography with Large-Volume Injections by Using Temperature-Assisted On-Column Solute Focusing

“…2,36–39 While a solvent gradient/reversed phase cLC system may not be highly susceptible to volume overload for the more hydrophobic solutes, the more polar solutes still can suffer from broadening due to volume overload. 36,38 Of course, which solutes in a sample fall into the “more polar” class and suffer volume overload and which do not because they fall into the “more hydrophobic” class depends on the injection volume and the particular chromatographic conditions. 36,38,40,41 Volume overload decreases the overall peak capacity and sensitivity of the method.…”

“…36,38 Of course, which solutes in a sample fall into the “more polar” class and suffer volume overload and which do not because they fall into the “more hydrophobic” class depends on the injection volume and the particular chromatographic conditions. 36,38,40,41 Volume overload decreases the overall peak capacity and sensitivity of the method. 36,38,39,42 Manipulating the gradient to avoid having solutes in the early eluting, “more polar”, class flies in the face of gradient optimization 37,43–45 which attempts to use all of the peak capacity available in the specified separation time.…”

Advances in and prospects of microchip liquid chromatography

“…To increase the pressure range of integrated packed beds, the use of metal substrates has been implemented to improve device strength. Titanium microchips containing 320 μm column channels packed with sub-2 μm porous particles that have pressure limits exceeding 1,000 bar have been reported [24,25]. The columns were used to study peak focusing in gradient elution.…”

“…Improvements in both device robustness [24-26] and instrument integration [33-35,39,50] are enabling technology that will be required for high efficiency on-chip chromatographic separations. For low-cost separation techniques, monolithic stationary phases in polymeric chips can be implemented [42-50] and it is possible that further advances in embossing techniques to generate pillar array columns [61] could eventually lead to disposable, one-use chromatography columns.…”

“…An important question is if microfluidic LC research will (or should) focus on pushing the limits of separation efficiency or on rugged, portable, fast separations of targeted analytes [3]. While the answer is still not clear, in the papers described here it would seem that industry is driving the technology for the former [11-13,24,25] while the biomedical research community is focused on the latter [37-39], with more traditional separations-focused groups falling somewhere in between. Perhaps it is in this region of overlap where high efficiency, fully portable LC devices may eventually come to fruition.…”