Development of Chip-based LC

Despite the comparative paucity of literature on chip-based LC, developments in the held of chip-based pressure-driven LC to date have shown that rapid analyses are possible, with virtually no solvent consumed (flow rates in the nanoliter per minute range vs. milliliter or even microliter per minute ranges), demonstrating the feasibility of this technology for on-line process applications, 

Initially modeled as flow between infinite plates, Giddings et al. [36] showed that the performance of rectangular geometry for open channel LC columns 

In a further development, Schlund et al. have conceived a hydrodynamic gated injection scheme [52] similar to that developed for electro kinetic flows by Ramsey s group. In this method, an injection cross is formed by the intersection of the separation channel with a bypass channel, analogous to the analyte loading channel in 4-port CE and CFG chips. Continuous streams of sample and mobile phase are fed into the chip hydrodynamically, while at the cross the flows converge in such a way that the mobile phase stream is diverted into the separation channel, and the sample stream is forced into the bypass channel. At the confluence of the 

Bottom row results from FEMLAB computational fluid dynamic simulation of process. 

Both open and packed columns have been demonstrated on LC and CEC chips. Strategies for making stationary phases in microchannels are few, and fall basically into three categories (a) standard HPLC packings, (b) monolithic phases, and (c) wall coatings or bonded, each of which is now discussed in turn. 

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