Chromatographic parameters porosity

Gel Permeation Chromatography. A Water Associates model 200 gel permeation chromatograph fitted with five Styragel columns having nominal porosity designations 107, 107,106, 1.5 X 105, and 1.5 X 104 A was used for the analysis of molecular weight distribution in TFE at a temperature of 50.0 0.5°C and a flow rate of 1.00 =t 0.05 ml/min. Further details concerning instrumental and operational parameters, sample preparation and injection, and data acquisition and reduction have been reported elsewhere (I). 

A liquid chromatographic column packed with 5.00 fim diameter solid support particles and having a porosity e = 0.400 is found to have a flow resistance parameter 750. Calculate the specific permeability K0. Assume that the flowrate/pressure drop relationship is identical to that of a bundle of identical parallel capillaries whose axes are spaced (in a square cross-sectional array) a distance of 5.00 /im from one another. What is the single capillary diameter of the hypothetical bundle ... 

The parameters defined in this chapter are divided into model parameters and evaluation parameters. Model parameters are porosity, voidage and axial dispersion coefficient, type and parameters of the isotherm as well as mass transfer and diffusion coefficient. All of them are decisive for the mass transfer and fluid flow within the column. They are needed for process simulation and optimisation. Therefore their values have to be valid over the whole operation range of the chromatographic process. Experimental as well as theoretical methods for determining these parameters are explained and discussed in Chapter 6. 

This noninvasive method could allow the differentiation between the various packing materials used in chromatography, a correlation between the chromatographic properties of these materials that are controlled by the mass transfer kinetics e.g., the coliunn efficiency) and the internal tortuosity and pore coimectivity of their particles. It could also provide an original, accurate, and independent method of determination of the mass transfer resistances, especially at high mobile phase velocities, and of the dependence of these properties on the internal and external porosities, on the average pore size and on the parameters of the pore size distributions. It could be possible to determine local fluctuations of the coliunn external porosity, of its external tortuosity, of the mobile phase velocity, of the axial and transverse dispersion coefficients, and of the parameters of the mass transfer kinetics discussed in the present work. Further studies along these lines are certainly warranted. 

Figure 41.15 shows the fractograms obtained from high-speed runs with sedimentation FFF (system Sed I) and flow FFF (Flow II) on five different chromatographic support materials. The fractograms look fairly similar, but, as noted earlier, they bear different information on size and density parameters. As already noted, the fractograms for sedimentation FFF (Figure 41.15a), when used in conjunction with microscopy, yield density and porosity information, as summarized in Table 41.6. With the density and... 

Molecularly imprinted polymers are highly cross-linked thermosets, and therefore porosity has been a necessary feature of their morphology to allow permeability and transport of template molecules to the bulk polymer phase. A high internal surface area ensures that the vast majority of the polymer mass is within several molecular layers of the surface and allows access of the template molecules to the majority of the polymer mass. A broad distribution of pore sizes is desirable for the use of these materials in chromatographic applications. Mesoporosity of amorphous porous materials is most commonly evaluated using a porosimeter by analyzing the N2 adsorption/desorption isotherms. Parameters that can be obtained from the measurements include surface area, average pore size, and pore size distribution. 

The method of synthesizing chromatographic packing materials yields porous particles. Porosity is an important parameter, and in SEC the size of the pores. 

Using chemical methods to polymerize liquid precursors into a continuous porous mass of coalesced particles, two sets of parameters can be controlled simultaneously. The nature of the material, porosity, and other properties that affect separations can be optimized. The size of channels and open spaces can be controlled independently. Monoliths for chromatographic use can be described as spongy with micrometer-sized channels winding through a mass of fused particles [3]. 

The peak dispersion in chromatography is generally characterized by the theoretical plate height (H) and the number of theoretical plates (N). The treatment of the mass transfer processes and the distribution equilibrium between the mobile and stationary phase in a column lead to equations that link the theoretical plate height as the crucial column performance parameter to the properties of the chromatographic systems, such as the linear velocity of the mobile phase, the viscosity, the diflusion coefficient of analyte, the retention coefficient of analyte, column porosity, etc. 

---