Solution pH and ionic strength

The release of non-Brownian particles (diameter s 5 pm) from surfaces has been studied. The influence of several variables such as flow rate, particle size and material, surface roughness, electrolyte composition, and particle surface charge has been considered. Experiments have been performed in a physically and chemically well-characterized system in which it has been observed that for certain particle sizes there exists a critical flow rate at which the particles are released from surfaces. This critical flow rate has been found to be a function of the particle size and composition. In addition, it has been determined that the solution pH and ionic strength has an effect on the release velocity. 

The critical velocity depends on particle radius, particle composition fluid medium, and fluid conditions such as solution pH and ionic strength. 

Detailed experimental procedures have been previously reported (Ko, 1998 Ko et al., 1998a,b) therefore, they are only briefly described here. Phenanthrene (Aldrich, 99.5+%), naphthalene (Aldrich, 99+%), SDS (Sigma, 99.5+%), and Tween 80 (Aldrich, no purity reported) were used as received selected physicochemical properties for these compounds are shown in Table 1. Kaolinite, a nonswelling 1 1 layer phyllosilicate clay and common constituent of many subsurface environments, was used as received from Sigma. Solution pH and ionic strength were adjusted as necessary with 0.5 M HC1 and/or 0.5 M NaOH and NaCl, respectively. Aqueous phenanthrene and naphthalene concentrations were quantified by fluorescence (PTI, Inc.) at the excitation/emission wavelengths of 250/364 and 278/322 nm, respectively. A total organic carbon (TOC) analyzer (Shimadzu Model 5050) was used to determine aqueous SDS concentrations and Tween 80 concentrations were determined by UV absorbance at 234 nm. 

A similar argument [7] was presented by Muller et al. [227] in their incisive analysis of adsorption of weak electrolytes from aqueous solution on ACs The solid surface charges in response to solution pH and ionic strength the resulting (smeared) surface electrostatic potential influences the adsorption affinity of the ionized solute. ... 

S. Saksena and A.L. Zydney, Effect of solution pH and ionic strength on the separation of albumin from immunoglobulins (IgG) by selective filtration. Biotech. Bioeng. 43 (1994) 960-968. 

This chapter shows that a unified explanation can be given of the adsorption from dilute aqueous solutions of different organic solutes, from nonelectrolytes to electrolytes, polyelectrolytes, and bacteria. Thus, the adsorption process is a complex interplay between electrostatic and nonelectrostatic interactions. Electrostatic interactions depend on the solution pH and ionic strength. The former controls the charge on the carbon surface and on the adsorptive... 

FA molecules, the strongest influence appeared to be due to organic concentration (23, 24). Solution pH and ionic strength can, however, play important roles at low FA concentrations (23). 

However, in spite of this vast literature it is generally difficult to compare the results from different authors. This is because the adsorption capacity and the rate of adsorption of metal ions by these biopolymers depend on a number of factors such as the physical state of the polymer (powder, flakes, or even if was reprecipitated), its degree of crystallinity, the degree of acetylation and the chain length. Temperature, stirring rate, contact time with the metal ion solution, pH and ionic strength, are also factors that influence adsorption. 

Palecek S.P. and Zydney A.L., 1994a. Hydraulic permeability of protein deposits formed during microfiltration Elfect of solution pH and ionic strength, J. Mem. Sci., 95,71. 

The polar nature of proteins causes them to bind multiple molecules of water, the number of which depends on solution pH and ionic strength. For proteins, the degree of hydration commonly varies from 0.3 to more than 1.0. Cantor and Schinunel [7] calculated that a monolayer of water bound to the surface of a 30,000-Da spherical protein would cause a 13.6% increase in the hydrated molecular radius. It is apparent that the relative degree of hydration will cause... 

Table 1 Dependence of the observed electrophoretic mobilities of dodecylpyridinium bromide and Triton X-100 on the carrier electrolyte solution pH and ionic strength...

McCormick et al. reported reversible self-locked micelles from a dually responsive triblock copolymer [113]. In this system, protonation of the pH-responsive block led to the formation of micelles that were subsequently cross-linked through electrostatic interactions of the zwitterionic middle block. The micellization and cross-linking processes were reversible, triggered by changing solution pH and ionic strength. 

All of the states of protein-polyelectrolyte complexes referred to above may be achieved by the selection of the polyelectrolyte (PE), choice of ionic strength and pH, and control of the concentration of the macromolecular components. Most reports on the practical applications of protein-polyelectrolyte complexes concern the effects of these factors. This chapter focuses on the effects of polymer charge density, solution pH and ionic strength on protein-polyelectrolyte com-plexation discussed in recent and current research. Techniques employed in the study of protein-polyelectrolyte complexes and applications of the complex to protein separation and enzyme immobilization are also described. 

For solution pH and ionic strength adjustment For solution pH and ionic strength adjustment For solution pH and ionic strength adjustment... 

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