Migration Direct measurement

The capacity factor k to be discussed shortly, is an alternate measure of retention. While k is used more often than R in chromatography, the use of R is advantageous because (i) it is directly proportional to peak migration velocity and is thus a more direct measure of retention than k (ii) most equations describing chromatography are simpler when expressed in terms of R rather than k and (iii) R is a more universal measure of retention R but not k applies to other perpendicular flow methods such as field-flow fractionation. 

In most cases the necessary material constant can be determined by direct measurement. In practice however, because of the time and cost required to measure the numerous types and combination possibilities of plastics and contacting media, only a limited selection of such experimental constants is available. Consequently in practice one cannot avoid using estimated values. Such estimations are possible within a degree of accuracy adequate for practical purposes, when the chemical structure of the migrating substance, the polymer and the contacting media are known. Thermodynamic terms are used to characterize the equilibrium distribution of a diffusant substance between plastic (P) and contacting media (e.g. a liquid L). The most important of these terms is the chemical potential i. 

Ammonium ion and Valency.—Although no direct measurement of the electroaffinity of the ammonium ion has been possible, the slight tendency to hydration of its salts indicates that it is stronger than the potassium ion. It is colourless, and the migration-velocity at 18° C.3 is given as 64-2, and at 25° C.4 as 73. Like the alkali-metals, the radical ammonium is univalent, and forms salts with one equivalent of an acid. 

Nutrient Transport by Fish Migration Many estuarine organisms can readily migrate between tidal creeks and the marsh platform and this migration can represent an appreciable flux of inorganic and organic N. Direct measurements of aquatic faunal... 

Also results obtained by means of mass transport method are listed as iep . In this method the mass of particles migrated through a orifice is directly measured, and this mass is related to the electrophoretic mobility by the following equation [54] ... 

An additional benefit to be derived from direct measurements of k2 involves its relation to rates of exciton migration using the theory of diffusion controlled processes. The rate constant for a purely diffusion controlled reaction may be written in the form (10)... 

The kinetics of oxygen migration in two compounds have been directly measured from N.M.R. measurements. The exchange process... 

Process analysis means analysing samples from a process in real-time as distinct from waiting until the end of the process to take samples for subsequent analysis in a laboratory. In recent years, this has meant the migration of certain analytical testing from the laboratory into production and direct measurement at sampling points during manufacturing. The data obtained are used to control the process itself, and hence the quality of the products made. Process analysis is now a substantial area for use of analytical instruments. 

Polarization is a prerequisite for neutrophil migration thus this assay is a [125, 170] measure of migratory potential, but not a direct measure of motility. 

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