Channel Configuration and Construction Limitations

In thermal FFF the temperature gradient across the channel thickness is maintained by the electrical heating of a polished metal block (usually a chrome or nickel-plated copper block) forming one wall and a cooled similar block forming the opposite wall. The plating improves resistance to corrosion, the factor limiting the range of permitted solvents and the separated particles and macromolecules. Cooling is usually accomplished by passing cold water through longitudinal holes bored in the block. To prevent thermo-gravitational convection, it is the upper block that is heated and the bottom one cooled. Thermocouples are mounted in the blocks to control their temperatures. In the bottom block, capillaries for the introduction and elution of the solvent and the sample are placed. The copper blocks are separated by a spacer of a polymer material with a low thermal conductivity (Mylar, Kevlar, etc.) to provide high temperature gradients. The channel constructions are described more exactly in the literature (see Further Reading). One of the main advantages of the FFF family stems from the uniform open channel geometry and the well-defined flow profile. As a consequence, retention can be related directly to the physicochemical parameters of the analyte material and carrier liquid. Possible deviations of the flow profile and the polymer parameters due to the non-uniform temperature distribution have been described.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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