The CE Process

Fast pre-equilibration processes may also accompany a reversible electrode reaction. Reactions involving preceding reaction steps are commonly observed in processes in which deprotonation, dehydration, or breaking of a metal-ligand bond occurs [101]. The mechanistic scheme for the CE case is given in Eq. II. 1.25, and cyclic voltammograms for this reaction sequence are shown in Fig.II.1.22. 

For the simulation of the cyclic voltammograms, an equilibrium constant K=0.01 has been selected so that only a small amount of the intermediate B is 

The reaction layer thickness for the CrevErev process may be written as reaction = (D/[/Cf + /Cb]) od, combined with the appropriate diffusion layer thickness (see Table II. 1.2), the kinetic parameter becomes A=dpeak/ 5i 

471Kinetic analysis of the CE-type reaction is often based on steady-state techniques such as rotating disc voltammetry [102]. 

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Figure 12.23 Label-free method for aptamer-based recognition of cocaine from its hydrolysate (ecgonine) using CE-ECL analysis assisted by an ionic liquid selector. An ionic liquid was used as the selector for the sample injection in the CE process, enriching cocaine and excluding the cocaine-aptamer complex and ecgonine from the capillary. [From T. Li et al. (2007a), with permission. Copyright 2007 Wiley.]...

Almost all operational modes of capillary electrophoresis have been combined with mass spectrometry via CF-FAB [68-70], MALDI [57,71], and ESI [72-76]. Of these three technologies, ESI has attained an enviable status as the interface of choice to couple CE with mass spectrometry. A CE/MS interface must address the problem of the low liquid flow rates of the CE process. Other considerations are buffer compositions and electrical contact between the separation buffer and the interface. As with LC/MS systems, only volatile buffers are tolerated in a CE/MS operation. Also, high salt concentrations must be avoided for stable operation of a mass spectrometry system. 

CE is not a method, nor a tool. It is a concept, a way of thinking, requiring many methods and tools to realize. Although the term, coined in the 1980s, has long been used, it has been replaced by many other terms indicating collaboration and information exchange between various disciplines and functions, and different cultures. As such, CE requires a socio-technical approach in which the social environment is taken into account wherein the product and process development process of CE takes place. There is massive interaction between this social environment and the CE process. 

In the next section the complex system of CE is further explored together with the encompassing production system that is both the result of the CE process and a constraint for it. 

Any design process is necessarily an iterative process requiring successive redesigns and modifications. The CE process should ensure that the effects of a change incorporated by one team on other design aspects are automatically analyzed. Moreover, the affected functional units should be notified of the changes. 

The CE process must facilitate an appropriate trade-off analysis leading to product-process design optimization. Conflicting requirements and constraint violations must be identified and concurrently resolved. 

Trends in the organization and structure of the CE process involve systems thinking and trans-disciplinarity. 

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