Liquid chromatography on-chip

Liquid chromatography on-chip: progression towards a μ-total analysis system

“…The miniaturised liquid chromatography chips were fabricated using standard photolithography, wet and dry chemical etching, and bonding techniques described previously. 4 Chip layout was designed on a Sun Sparc workstation at the National Microelectronics Research Centre (Cork, Ireland). The separation channels and intersection for injection (Fig.…”

“…The chromatographic efficiency was low, due to a number of factors including the volume of injection. 4 In this more recent work the on-chip retention of a pharmaceutical drug substance, caffeine, is demonstrated. The separation mchannels (100 mm in width, 5.3 mm in depth, 16 cm in length) were chemically modified with an n-octyltriethoxysilane phase (0.5 g of n-octyltriethoxysilane in 5 ml of toluene) and then interfaced with the nano-LC system (micro-pump and UV detector with 3 nl flow cell).…”

“…11 With on-chip microelectrodes, conductometric detection of sodium nitrate has previously been shown. 4 However, amperometric detection is also possible with the on-chip electrodes. Amperometric detection was performed in the three-electrode mode with the upstream electrode as the working electrode and the electrode closer to the exit as counter electrode, respectively, together with an external Ag/AgCl reference electrode.…”

“…3 While tremendous advances have been made in the miniaturisation of capillary electrophoretic separation systems, the challenges of microfabrication of an efficient m-LC system remain. 1,2,4 By exploiting micromachining technologies it is relatively easy to fabricate a large number of columns reproducibly; however there are a number of problems, in particular the sealing of the m-channels to allow the mobile phase to be pumped through the chip at pressures exceeding 2000 psi. Also, there are many difficulties associated with coupling to external instrumentation without leakage and without the introduction of dead volumes.…”

Electrically actuated, pressure-driven liquid chromatography separations in microfabricated devices

“…Despite the challenges it presents, the miniaturization of pressure-driven separation methods is of great interest; 5,7,8 however, most reports have focused on micromachining a separation column while maintaining an external pumping mechanism. [9][10][11][12][13][14][15][16][17] Thus, the full advantages of LC miniaturization were not realized. Two recent studies have made important progress in the development of miniaturized LC systems with integrated pumping and injection.…”