Fabrication of Nanocolumns for Liquid Chromatography

TLDR: In situ micromachining can be used to simultaneously position and define support particles, convective transport channels, an inlet distribution network of channels, and outlet channels in multiple chromatography columns on a single quartz wafer to the level of a few tenths of a micrometer.

Abstract: This paper shows that in situ micromachining can be used to simultaneously position and define (i) support particles, (ii) convective transport channels, (iii) an inlet distribution network of channels, and (iv) outlet channels in multiple chromatography columns on a single quartz wafer to the level of a few tenths of a micrometer. Stationary phases were bonded to 5 × 5 × 10 μm collocated monolith support structures separated by rectangular channels 1.5 μm wide and 10 μm deep with a low degree of deviation of channel width between the top and bottom of channels. High aspect ratio microfabrication can only be achieved with deep reactive ion etching. The volume of a 150 μm × 4.5 cm column was 18 nL. Column efficiency was evaluated in the capillary electrochromatography (CEC) mode using rhodamine 123 and a hydrocarbon stationary phase. Plate heights in these columns were typically 0.6 μm in the nonretained and 1.3 μm in the retained modes of operation. Columns were designed to have identical mobile-phase vel...