ElFFF and Related Electrophoretic Methods

The nearest relatives of ElFFF are different elec-trophoresis techniques in liquids. However, elec-trophoresis systems often require very high field strengths for resolution, and the high voltages are limited by the Joule heating. Particle electrophoretic mobilities should also be high enough to have an acceptable resolution in common capillary lengths. Another type of electrophoresis separation system, free-flow electrophoresis, utilizes an electric field across a curtain of buffer between two vertical plates (a principle very close to FFF) and allows for continuous sample injection, but limits the detection and collection systems to the certain number of fractions. Resolution in free-flow electrophoresis is limited by fraction spreading in the fluid stream caused by the parabolic flow profile. Other methods of separating molecules and cells are needed for applications, where these limitations preclude the use of existing systems. Field flow fractionation is the solution for some applications, where particle electro-phoretic mobilities are too low for the conventional electrophoresis systems and high electric field strengths are not desirable. ElFFF has all the advantages of FFF systems, i.e., the ability to separate cells, large molecules, colloids, emulsions, and structure, which are too delicate for electrophoretic separation such as liposomes, both in the 'original' condition and after surface modification. Unlike the free-flow electrophoresis systems, elution in FFF systems is zonal and proceeds through one outlet port; for this reason, it is capable of significantly higher resolution. Therefore, anticipated applications of ElFFF systems include cell separations, characterization of emulsions, liposomes, and other particulate vehicles for intravenous drug administration with respect to size, charge, and stability, diagnostic tests for specific molecules in colloidal suspensions, quick and accurate separations of molecules, environmental water monitoring, tests for sample contamination, and further research involving zeta-potentials. ElFFF systems also find application as sample pretreatment systems by performing an initial separation on a sample, which is later collected for further testing by another analysis system.

The resolution of ElFFF is determined in the standard way for chromatography, i.e. by the comparison of the sum of the peak dispersions for two neighbouring peaks to the difference of their maxima. The resolution of ElFFF is inversely proportional to the separation distance of the electrodes; thus, the smaller the distance between the channel walls, the higher the resolution between two distinct particles, making ElFFF an ideal application for using micro-machining techniques. The resolution increases with the square root of the channel length, so the longer the channel the better the resolution, but the time required for the improved resolution increases, which is not generally desirable.

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.

Get My Free Ebook


Post a comment