Electrokinetic platform

The electrokinetic platform uses electric charges, fields, field gradients or temporally fluctuating electrical fields for liquid actuation. The actuation is provided between different electrodes, and several effects (eletrophoresis, dieletrophoresis, osmotic flow, polarization) superimpose each other, depending on the sample liquid. Besides liquid actuation, the effects can also be used for separation of molecules and particles, detection, and catalysis. 

Figure 14. Microfluidic realization of capillary electrophoresis analysis on the electrokinetic platform. (Adapted from [123], ( Agilent Technologies, Inc. 2007. Reproduced with permission, courtesy of Agilent Technologies, Inc.) After the sample has been transported to the junction area (a) it is metered by the activated horizontal flow and injected into the separation channel (b). Therein, the sample components are electrophoreticaUy separated (c) and readout by their fluorescence signal (d). The complete microfluidic CE-chip is depicted in the center.

Lvovich VF, Matthews E. AC electrokinetic platform for iontophoretic transdermal drug dehvery. J Control Release. 2010 Apr 24. [Epub ahead of print]... 

The first chapter discusses the various electrokinetic interactions that govern migration and separation of different sample components in two of the most commonly used electrodriven analytical techniques—CZE and CEC—in order to provide a platform of fundamental understanding for more detailed and specific chapters that follow. 

Capillary electrophoresis (CE) is a powerful separation technique. It is especially useful for separation of ionic compounds and chiral mixtures. Mass spectrometry has been coupled with CE to provide a powerful platform for separation and detection of complex mixtures such as combinatorial libraries. However, the full potential of CE in the application of routine analysis of samples has yet to be realized. This is in part due to perceived difficulty in the use of the CE technique compared to the more mature techniques of HPLC and even SFC. Dunayevskiy et al. [136] analyzed a library of 171 theoretically disubstituted xanthene derivatives with a CE/ESI-MS system. The method allowed the purity and makeup of the library to be determined 160 of the expected compounds were found to be present, and 12 side products were also detected in the mixture. Due to the ability of CE to separate analytes on the basis of charge, most of the xanthene derivatives could be resolved by simple CE-MS procedures even though 124 of the 171 theoretical compounds were isobaric with at least one other molecule in the mixture. Any remaining unresolved peaks were resolved by MS/MS experiments. The method shows promise for the analysis of small combinatorial libraries with fewer than 1000 components. Boutin et al. [137] used CE-MS along with NMR and MS/MS to characterize combinatorial peptide libraries that contain 3 variable positions. The CE-MS method was used to provide a rapid and routine method for initial assessment of the construction of the library. Simms et al. [138] developed a micellar electrokinetic chromatography method for the analysis of combinatorial libraries with an open-tube capillary and UV detection. The quick analysis time of the method made it suitable for the analysis of combinatorial library samples. CE-MS was also used in the analysis... 

Abstract. Programmable manipulation of particles or cells plays an important role in many biological and medical applications. Here a new programmable micro manipulator, named lab-on-a-display, in which particles are manipulated by optically induced electrokinetic forces generated from an optoelectronic tweezers on a liquid crystal display, is introduced. This optoelectrofluidic platform has been utilized to manipulate various kinds of cells such as blood cells, oocytes, and motile bacteria for several biotechnological applications. 

The hrst pTAS devices were based on GC. Soon after, HPLC-based pTAS platforms began to appear and then CE followed. In chip CE, an injection was performed and an electrophoretic separation of a sample mixture (different fluorescent dyes) and all liquid handling was achieved using electro-osmotic flow. Since then, electrophoresis and electrokinetic fluid handling have been the cornerstones of many miniaturised analytical devices. 

Research stiU continues into the development of enhanced electrokinetic injection techniques for p-chips. Modifications made to the outlet end of the separation channel, such as its connection to a length of fused silica capillary to facilitate chip interfacing with off-chip detection systems for example, can be adopted equally well for chip inlets and sample introduction. The use of conventional capillary to interface between macroscale sample reservoirs and p-chip platforms has been successfully... 

ID Separation of Proteins There has been considerable research devoted to tbe development of nricioflu-idic platforms capable of performing small-scale protein separations. In addition to diffusion based methods [3], nearly every type of electrokineticaUy driven separation has been demonstrated in a cbip-based platform, including free-flow electrophoresis, capillary electrophoresis, capillary gel electrophoresis, isoelectric focusing (lEF), micellar electrokinetic chromatography and capillary electrochemical chromatography. 

Related to the assessment of heavy metals which are alarming in foods, ME-AD approach has also been reported for their determination in juice samples [38], East detection of prominent heavy metals (lead, cadmium, and copper) has been demonstrated on ME-AD platforms using CSPEs. Chemical separation (25 mM MES/L-histidine buffer solution of pH 7.0), electrokinetic conditions (-1-1200 V, 3 s injection), and detection potential (-0.8 V) were carefully optimized. Excellent recoveries in spiked juice samples (without oxygen-free condition) ranging from 92% to 108% (n = 10) were obtained, giving in addition an excellent reproducibility (RSDs < 7%). 

The analytical suitability of the electrokinetic microfiuidic platform with MWCNTs as detectors was further proposed based on its dual format/use as a flow and separation system, independently as it is depicted in Figure 12.7. Relevant applications of high significance, determination of total isofiavones, and fast detection of antioxidant profiles (arbutin. 

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