Linear chromatography definition

Evaluation parameters are retention time, selectivity, efficiency or plate number, HETP values and resolution. They characterize the performance of a certain chromatographic separation and are indicators for the selection (or better definition) of a chromatographic system. Strictly speaking they are defined for linear chromatography only. 

Poppe and Kraak [29] have defined the apparent plate number by extending the definition given in linear chromatography... 

Resolution In linear chromatography, the resolution is defined as the ratio of the difference between the retention times of the maxima of two successive bands and their average width. The definition is valid in nonlinear chromatography as well, but has limited interest. 

As discussed previously (Chap. 10.4), the band profile in linear chromatography is Gaussian. The relative standard deviation of this Gaussian profile is used as a way of characterizing column efficiency. By definition... 

Finally, an officially updated definition of the retardation factor, R, issued by lUPAC is important to the whole field of planar chromatography (the linear and the nonlinear TLC mode included). The importance of such a definition has two reasons. First, it is promoted by the growing access of planar chromatography users for densitometric evaluation of their chromatograms and second, by the vagueness of the present definition in the case of skewed concentration profiles with the samples developed under mass overload conditions. 

The simple definition of chitinase activity, EC 3.2.1.14, "hydrolysis of iV-acetyl-D-glucosaminide (l-4)-P-linkages in chitin and chitodextrins", belies the complexity and diversity of this group of enzymes. When chitinolytic organisms are investigated in detail, they are found to produce a range of chitinase activities. Usually these can be separated readily by chromatography or electrophoresis. However, it is more difficult to define their precise activities, chiefly because of the uncertain nature of the available assays for chitinases, with non-linear time courses... 

Readers interested in a definitive treatment of linear adsorption chromatography should consult the book Principles of Adsorption Chromatography by L. R. Snyder (2). Although written a decade ago, the book contains an extensive and still entirely valid presentation of the subject and forms one of the main sources used in writing this article. 

Rhee et al. developed a theory of displacement chromatography based on the mathematical theory of systems of quasi-linear partial differential equations and on the use of the characteristic method to solve these equations [10]. The h- transform is basically an eqmvalent theory, developed from a different point of view and more by definitions [9]. It is derived for the stoichiometric exchemge of ad-sorbable species e.g., ion exchange), but as we have discussed, it can be applied as well to multicomponent systems with competitive Langmuir isotherms by introducing a fictitious species. Since the theory of Rhee et al. [10] is based on the use of the characteristics and the shock theories, its results are comprehensive e.g., the characteristics of the components that are missing locally are supplied directly by this theory, while in the /i-transform they are obtained as trivial roots, given by rules and definitions. 

As the third option was one where considerable hands-on experience was available, our chromatography-based procedure definitely had to be kept alive in the sense that development resources were justified for improving the performance. However, a forecast of 5 kg production simply by linearly extrapolating data from the A kg batch, resulted in a really frightening scenario where considerable manpower (peak values of 20-30 people during certain stages) had to be allocated over... 

In size exclusion chromatography, components are excluded from the resin on the basis of size. By definition, solutes are not absorbed. These supports have a linear equilibrium, since a constant volume within the resin is available for a given size solute. When the support comes to equilibrium with the mobile phase, the volume in the pores available to the solute will have the same molar concentrations as the surrounding mobile phase. 

The retention and the selectivity of separation in RP and NP chromatography depend primarily on the chemistry of the stationary phase and the mobile phase, which control the polarity of the separation systems. There is no generally accepted definition of polarity, but it is agreed that it includes various selective contributions of dipole-dipole, proton-donor, proton-acceptor, tt-tt electron, or electrostatic interactions. Linear Free-Energy Relationships (LFER) widely used to charactaize chemical and biochemical processes were successfiiUy apphed in liquid chromatography to describe quantitative structure-retention relationships (QSRR) and to characterize the stmctural contributions to the retention and selectivity, using multiple linear correlation, such as Eq. 

The Revalue is the fundamental parameter in planar chromatography to describe the position of a spot on a developed chromatogram. values in linear, circular, and anticircular chromatography were defined. Correlations between these types of R were evidenced for conversion of linear R values in circular and anticircular and unidimensional multiple development. Definition of thermodynamic and relative Revalues were also reported and discussed. In addition, the importance of Rm value, which has a linear relationship with structural elements of the solute and can be used to characterize molecular hydrophobicity in reversed planar chromatography, was evidenced. 

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