Frontal analysis, chromatography

Modes of Operation The classical modes of operation of chromatography as enunciated by Tisehus [Kolloid Z., 105, 101 (1943)] are elution chromatography, frontal analysis, and displacement development. Basic features of these techniques are illustrated in Fig. 

Y Ishihama, T Miwa, N Asakawa. Drug-plasma protein binding assay by electrokinetic chromatography-frontal analysis. Electrophoresis 23 951-955... 

There is a dearth of competitive adsorption data, in a large part because they are difficult to measme, but also because little interest has been devoted to them, as, until recently, there were few problems of importance whose solution depended on their understanding. Besides the static methods, which are extremely long and tedious and require a large amoimt of material, the main methods of measurement of competitive isotherms use column chromatography. Frontal analysis can be extended to competitive binary isotherms [14,73,93-99], as well as pulse techniques [100-104]. The hodograph transform is a powerful method that permits an approach similar to FACP for competitive binary isotherms [105,106]. 

Frontal chromatography frontal analysis, form of chromatography where the sample is continuously added to the column. Only the least retained component in a sample mixture is obtained in a pure form, the other components co-elute. 

In ideal chromatography, frontal analysis results in the gradual extension of a band of adsorbate at constant concentration down the column, assuming constant column temperature and constant partial pressure of adsorbate in the gas entering the column. By equating total adsorbate introduced to the column to the amount present in the gas phase plus adsorbent phase in a band of length on the column, one arrives at f = (qL/P (CG + vA/P ) t, where t is total time of flow in minutes. In the case of a linear isotherm this is just = AF t, as one intuitively expects. ven if the isotherm is nonlinear, (v/P is constant everywhere in the band, for P constant. This... 

A chromatographic separation can be developed in three ways, by displacement development, by frontal analysis, and by elution development, the last being almost universally used in all analytical chromatography. Nevertheless, for the sake of completeness, and because in preparative chromatography (under certain conditions of mass overload) displacement effects occur to varying extents, all three development processes will be described. 

Several variants of separation methods based on dialysis, ultrafiltration, and size exclusion chromatography have been developed that work under equilibrium conditions. Size exclusion chromatography especially has become the method of choice for binding measurements. The Hummel-Dreyer method, the vacancy peak method, and frontal analysis are variants that also apply to capillary electrophoresis. In comparison to chromatographic methods, capillary electrophoresis is faster, needs only minimal amounts of substances, and contains no stationary phase that may absorb parts of the equilibrium mixture or must be pre-equilibrated. 

Tiselius, A. Developed liquid chromatography and pointed out frontal analysis, elution analysis, and displacement development. 

Computer-aided frontal analysis chromatography can be used to determine surface areas and adsorption isotherms (4). Both permanent gases and adsorbates that are liquids above room temperature could be used in this system. 

Figure 10.2. A comparison of zonal chromatography with frontal analysis.

Flame ionization detector (FID), 126-129 Flash chromatography, 222, 280 Fast LC, 200 Flow, measurement of, 63 Flow programming, 8, 150 Flow resistance parameter, 64 Fluorescence detector, 207-208 Frontal analysis, 6... 

The chromatographic process we have defined is also known as zonal or batch chromatography because the sample is applied to the system all at once in one narrow zone. By contrast, the sample can be applied continuously during a run this process is called frontal analysis, and it will not be discussed further because of its limited use. 

In a modification of "solid-liquid adsorption chromatography , known as frontal analysis, or break-throughfintxoduced by A. TiseliuS in 1940-43), the sample soln is continuously passed thru the column until the latter has become satd with the solutes, ie until the compn of the soln leaving the column would be identical with that of the soln entering the column (Ref 78,p 69). Concns of solns leaving the column may be approx detd by the use of an optical system registering changes in... 

It is well known that drugs bind to plasma proteins, particularly to serum albumin and a-acid glycoprotein, and that only the unbound, or free, fraction is responsible for any pharmacological effect. For protein-drug binding studies size-exclusion chromatography in one of three variants—namely, the Hum-mel-Dreyer method (1962), the vacancy peak method (Sebille, et al., 1979), and frontal analysis (Cooper and Wood, 1968)—is the traditional method of... 

It is to be noted that with complete flow reversal the separation process in column I is the analogue of the frontal separation process or the frontal analysis in a flxed bed of the sorbent the separation process in column II is the analogue of the reverse frontal analysis and the process in both columns, with conditions, phase composition, and temperature unchanged in passing from one column to the other is the analogue of displacement chromatography. The analogy is related only to the... 

In the frontal analysis experiment described in Section 5.3.2, the transport model of chromatography was used to fit the experimental data [40]. Neglecting axial and eddy diffusion, band broadening was accounted for by one single mass transfer rate coefficient. The mass transfer rate coefficients estimated were small and strongly dependent on the temperature and solute concentration, particularly the rate coefficients corresponding to the imprinted L-enantiomer (Fig. 5.12). Above a concentration of ca. 0.1 g/L the mass transfer rate coefficients of the two enantiomers are similar. 

One of the most important applications of frontal chromatography is the determination of equilibrium adsorption isotherms. It was introduced for this purpose by Shay and Szekely and by James and Phillips [4,5], The simplicity as well as the accuracy and precision of this method are reasons why the method is so popular today and why it is often preferred over other chromatographic methods e.g., elution by characteristic points (ECP) or frontal analysis by characteristic points (FACP) [6,7]. Frontal chromatography as a tool... 

There are two possibilities for performing a frontal chromatography experiment for the purpose of the determination of equilibrium isotherms. The step-series method uses a series of steps starting from C = 0 to C +i. After each experiment, the column has to be reequilibrated and a new step injection with a different end concentration C +i can be performed. In the staircase method, a series of steps is performed in a single run with concentration steps from 0 to Q, Q to C2,.. ., C to C +i. The column does not have to be reequilibrated after each step and, therefore, the staircase method is faster than the step-series method. Both modes of frontal analysis give very accurate isotherm results. 

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