Micro Total Analysis Systems Lab-on-a-Chip

The lab-on-a-chip concept is undergoing a rapid development phase at present, in contrast with the maturity of many of the other technologies that are discussed in this book indeed, the Royal Society of Chemistry (UK) has started publishing a new journal with this very title (http //www.rsc.org/Publishing/Journals/lc/index. asp). Biennial reviews of this field (Reyes 2002 Auroux 2002 Vilkner 2004 Dittrich 2006) provide ample evidence that any attempt here to describe the current state-of-the-art would be rapidly out of date, so the main thrust will be focused on more fundamental concepts additional problems associated with interfacing such devices to mass spectrometry are discussed in Chapter 5. It should be mentioned that the current flurry of activity in this field has been driven mainly by applications to proteomics and other areas of modem molecular biology, rather than to trace quantitative analysis of small molecules some examples of the latter applications, of direct interest here, are also given in Section 5.2.3. 

The basic principles of scaling down bench scale apparatus to a size that can be accommodated on a chip, using 

The time t for analyte A to emerge from a CE column is simply  

This is good news for miniaturization, but does not address the important question of separation efficiency Na (do not confuse this with the Avagadro Constant) for analyte A. It is a very general resnlt (equation [3.20]) that  

This last result is important because it tells us that, provided that the device can withstand the same potential drop, as the length, Z, of the CE device is decreased, the separation efficiency is not affected by miniaturization so theoretically it is possible to obtain a significant decrease in analysis time (see above) without a loss in separation efficiency. 

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