Controlled-pore glass curve

A dry packed column with porous material was used for the characterization according to size of the PVAc latex samples. The packing employed was CPG (Controlled Pore Glass), 2000 A, 200-400 mesh size. Deionized water with 0.8 gr/lit Aerosol O.T. (dioctyl sodium sulphosuccinate), 0.8 gr/lit sodium nitrate and 0.4 gr/lit sodium azide served as the carrier fluid under a constant flowrate. The sample loop volume was 10 pC A Beckman UV detector operating at 254 nm was connected at the column outlet to monitor particle size. A particle size-mean retention volume calibration curve was constructed from commercially available polystyrene standards. For reasons of comparison, the samples previously characterized by turbidity spectra were also characterized by SEC. A number of injections were repeated to check for the reproducibility of the method. 

Fig. 1. Small angle x-ray scattering curves for Vyoor and controlled pore glasses (from lop to bottom) Vycor, CPG-120, CPG-170, and CPG-350. For clarity reasons, intensity is in arbitrary units. A Q" curve has been drawn as a guide to the eye.

To investigate the effects of the different mass transfer mechanisms, breakthrough curves were generated on model monoclonal antibody affinity columns with two types of packings Sepharose 4B (Pharmacia) and controlled-pore glass (Electronucleonics, mean pore size 1273 ft) Mouse monoclonal anti-benzenearsonate IgG was produced in this laboratory by batch culture in a 15 L fermentor. The IgG was purified... 

We review a recently developed molecular-based approach for modeling mercury porosimetry. This approach is built on the use of a lattice model of the porous material microstructure and the use of mean-field density fiuictional theory (MF-DFT) calculations and Monte Carlo simulations to calculate the three-dimensional density distribution in the system. The lattice model exhibits a symmetry between the adsorption/desorption of a wetting fluids and intnision/extrusion of a nonwetting fiuid. In consequence, macroscopic approaches used previously to transform mercury porosimetry curves into gas adsorption iso erms are essentially exact in the context of the model. We illustrate the approach with some sample results for intrusion and extrusion in Vycor and controlled pore glass (CPG). 

The kinetics of polymer adsorption on porous substrates is much more difficult to tackle. Besides adsorption, desorption, and exchange, size exelusion has to be taken into account. Also, most in situ methods are not applicable to porous substrates. A major difficulty is that with all available methods smeared-out properties are measured while it is likely that strong gradients in the axial direetion of the cylindrical pore are present. The process of axial equilibration is poorly understood and in many cases extremely slow. Most studies were performed with porous substrates with broad pore size and shape distributions. Controlled-pore glasses, zeolites, or porous membranes could be used as model systems with pores of molecular size. Application of glass capillaries is interesting for controlling the hydrodynamics in a curved system. 

More detailed investigations were carried out by Basedow and Ebert (2) on the degradation of narrow dextran fractions at an ultrasonic frequency of 20 kc/sec in many solvents. The concentration of the polymer was 0.5%. The moleixilar-weight distributions were obtained to high accuracy by permeation on controlled pore glass. In all experiments it was found that rupture occurs near the center of the molecule. A typical set of distribution curves of degradation products is drown in Fig. 23. Similar results were found by Bradbury and O Shea (P) for several proteins and Davison and Freifelder (16) for DNA. 

Figures 11.1 and 11.2 illustrate mercury porosimetry data of a bimodal size distribution. However, other types of less typical curves are often encountered. For example, samples of controlled porous glass exhibit intrusion-extrusion curves illustrated by Fig. 11.3, in which all the pores are essentially of one radius.

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