Fabrication of Nanocolumns for Liquid Chromatography

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 x 5 x 10 microns collocated monolith support structures separated by rectangular channels 1.5 microns wide and 10 microns 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 microns x 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 micron in the nonretained and 1.3 microns in the retained modes of operation. Columns were designed to have identical mobile-phase velocity in all channels in an effort to minimize outgassing during operation. When the total lateral cross-sectional area of channels at all points along the separation axis is identical, linear velocity of the mobile phase in a CEC column should be the same. Columns were operated at atmospheric pressure.

Core–Shell, Ultrasmall Particles, Monoliths, and Other Support Materials in High-Performance Liquid Chromatography

“…Pillar array columns were first proposed in 1998 for use under electrically driven flow conditions 95 . A pillar array can be considered as the 2-dimensional equivalent of the sphere packing in a packed bed.…”

New advances in microchip fabrication for electrochromatography

“…Quartz fabrication process by RIE technique results in high aspect ratio channels, and parallel plasma RIE using CHF 3 -based chemistry allows construction of very complex channel structures [11,44]. Quartz substrates can be cut by intensified CO 2 laser and then sandwiched with a cover and/or bottom plates, bonded at 11507C, to form a highoptical quality chip [10].…”

“…Commonly used substrates were different types of glass-or silica-based wafers, as well as optically superior quartz, because of their commercial availability from several manufacturers and their well-understood chemistry [10][11][12][13]. For glassy material microstructuring, standard photolithography and wet chemical or reactive ion etching (RIE) combined with standard deposition techniques is widely used.…”

Peer Reviewed: Polymeric Microelectromechanical Systems.

“…RIE. Plasma etching or reactive ion etching (RIE) is widely used for semiconductor fabrication and to produce quartz microchips for electrophoretic and chromatographic applications (6,7). In most cases, RIE is restricted to glass, quartz, or silicon.…”