Multiple development capillary flow

The multiplicity of phenomena characteristic of flow in heated micro-channels determined the content of the book. We consider a number of fundamental problems related to drag and heat transfer in flow of a pure liquid and a two-phase mixture in micro-channels, coolant boiling in restricted space, bubble dynamics, etc. Also considered are capillary flows with distinct interfaces developing under interaction of inertia, pressure, gravity, viscous and capillary forces. 

Development in TLC is the process by idiich the mobile phase moves through the sorbent layer, thereby inducing differential migration of the suple components. The principal development modes used in TLC are linear, circular and anticircular with the velocity of the mobile phase controlled by capillary forces or forced-flow conditions. In any of these modes the development process can be extended by using continuous development or multiple development. 

It has proven difficult to develop a theoretical model for multiple development under capillary flow controlled conditions and too little work has been done using forced-flow conditions for any concrete conclusions to be reached [135]. A model has been t... 

Figure 27.11 illustrates a third dual-electrode arrangement that permits enhancement of the response by reversible redox cycling. Many more electrons are therefore transferred than would be the case with a single electrode, and the current is amplified dramatically. This concept does not work well with conventional LC columns because the volume flow rate is too large to permit a significant number of redox cycles. Nevertheless, the concept is certainly interesting, and, as reversed-phase capillary columns are developed, it may well have some practical value. A detailed treatment of multiple-electrode LCEC has been published [24]. 

Equation (6.13) provides values that are about 25% smaller that those calculated by Eq. (6.12). Some typical results from theory or determined by experiment are summarized in Table 6.4. Results from theory are probably too high and represent an upper limit. Experiment indicates a zone capacity of about 12-14 for a single development with capillary flow. This rises to about 30 - 40 for forced flow. Automated multiple development with capillary flow provides a similar zone capacity to forced flow. Two-dimensional thin-layer chromatography employing different retention... 

Unidimensional multiple development provides a complementary approach to forced flow for minimizing zone broadening.All unidimensional multiple development techniques employ successive repeated development of the layer in the same direction, with removal of the mobile phase between developments. Approaches differ in the changes made (e.g., mobile-phase composition and solvent front migration distance) between consecutive development steps the total number of successive development steps employed can also be varied. Capillary forces are responsible for migration... 

A wide range of mobile and stationary phases combined with capillary flow and forced flow one- and two-dimensional and multiple and gradient development modes lead to high separation selectivity. 

Photometric detection, 208-210 Photomultipliers, 378-379 Physical methods of detection, 206-211 photometric detection, 208-210 visual detection, 206-208 Physical phenomena in TLC, 49-53 broadening of chromatographic spots, 50-53 capillary flow, 49-50 volatility of solvents, 53 Pigments. See Natural pigments Planar chromatography (instrumental TLC), 3, 129-148,373-385 automation in, 131,382-384 chromatogram development, 135-140 automated multiple development (AMD), 138-140... 

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