In gel chromatography

Another hydrophilic gel that has been successfully used in gel chromatography is the poly(acrylamide) type, first introduced in... 

There is at present no general agreement as to the best method of relating the elution volumes and Kd values in gel chromatography... 

Figure 11.9 Effects of liquid velocity and molecular weight on Hs in gel chromatography (dp 44 pm, 1.6x30 cm column).

In gel chromatography, the distribution coefficient K is little affected by the concentration of solutes, pH, ionic strength, and so on, and is considered to be constant. Therefore, the results obtained in. Section 11.6.2 for constant K can be applied to evaluate the performance of gel chromatography. Figure 11.9 shows the increase in Hs with the liquid velocity in gel chromatography packed with gel particles of 44 pm diameter [4]. The values of Hs increase linearly with the velocity, and the slopes of the lines become steeper with an increase in molecular weights, as predicted by Equation 11.20. 

Incubation of lake water with 32P or 33P as tracers and subsequent gel chromatography reveals that a major pathway exists between dissolved orthophosphate and the particulate phase (3, 5-7). Low-molecular-weight phosphorus forms in the presence of bacteria and algae. SUP is present in the low-molecular-weight fraction and is classified as individual DOP compounds unassociated with particulate or colloidal material. The HMW fraction found in gel chromatography studies is characterized as a colloid that contains phosphorus compounds or incorporates orthophosphate. The colloidal material then releases orthophosphate, replenishing the dissolved phosphorus cycle. In some eutrophic lakes the HMW SRP fraction can make... 

The media most commonly used in gel chromatography (otherwise termed gel filtration or molecular sieve chromatography) are the cross-linked dextrans (Sephadex), bead-form polyacrylamides (Bio-Gel P) and the bead form agaroses (Sepharose, Bio-Gel A, and Indubiose). It is on these gels that most data have been accumulated and the majority of interactions of interest occur. 

The major components of beef glomerular basement membrane were solubilized with sodium dodecyl sulphate and resolved on 6% agarose [229]. 0.1% SDS has also been used in the separation of lipoprotein and apolipoprotein from human plasma [230] and 3% SDS used in gel chromatography of human erythrocyte membranes on Sepharose 6B [231]. Stokes radius determination of insulin-binding protein was performed on Sepharose 6B with 0.5% Triton X-100 [232]. 

The preparation of a range of beaded methacrylate and acrylate beads for use in gel chromatography was described in a recent Japanese patent [236],... 

In some cases, several secondary processes may manifest themselves simultaneously. A typical combined secondary process is the so-called concentration effect in gel chromatography, i.e., the often observed rise of the retention volumes of macromolecular substances with the increased sample concentration. The concentration effect is caused by a decrease in the macromolecular coils dimensions in solution with growing concentration, further by viscosity and osmotic effects as well as by secondary exclusion — and in the case of soft gels also by altering the pore geometry due to deswelling of gel particles in the zone of the sample. 

The resolution power in gel chromatography is determined by both the efficiency and selectivity of the chromatographic system. 

The efficiency of a real GPC system depends above all on the rate of mass transfer between mobile phase and gel phase, as well as on the extent of secondary processes. Quantitatively, the efficiency can be expressed by the terms like width (w) or deviation (o) of the chromatographic peak, as well as by other terms of the theoretical plate concept. Since the diffusion rate of solute molecules decreases with an increase of their dimensions, one has to expect generally lower efficiency in gel chromatography of macromolecules in comparison with any other mode of liquid chromatographic separation of low molecular substances. 

In analytical practice, the logarithm of sample molar masses, or molar volumes, is plotted versus retention volumes in calibration dependences of low molecular substances while values or effective hydrodynamic volumes, are used as size parameters in gel chromatography of macromolecules [12,13]. is often called universal calibration parameter because in ideal gel chromatography of randomly coiled macromolecules, it enables the transfer of data from one polymer to another regardless of both the physical (linearity, branching, tacticity, etc.) and the chemical (composition) structure of macromolecules [12]. The hydrodynamic volume of a particular polymer is proportional to the product of its molar mass and limiting viscosity number [ij], in the solvent that is used as mobile phase [ij]Mm. 

Within certain limits, the majority of operational variables do not determine the results of gel chromatographic separations in a decisive way. Nevertheless, it is advisable to test all variables for each particular system and application in order to obtain optimal and reproducible data. The most common operational variables in gel chromatography are the volume, Uj, and the concentration, C, of the sample applied, both influencing the retention volumes and the separation efficiency. In analytical separations, it is necessary to work with the lowest v, and C allowed by the particular detection system (cf., section 4.6.3.6). The allowed sample volume depends primarily on the volume of the column and is usually several millilitres in the case of... 

Presently, the most important detectors in gel chromatography are the photometers and the differential refractometers. 

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