Adsorption hydrophobic

The addition of polar organic solvents to the eluent is recommended with the goal of decreasing the hydrophobic adsorption. The addition of salts to the eluent is also recommended when the sample is ionic (Eigs. 6.24-6.26, pages 198 and 199). 

The stationary phase in gel permeation (also called size exclusion) chromatography contains cavities of a defined size distribution, called pores. Analytes larger than the pores are excluded from the pores and pass through the column more rapidly than smaller analytes. There may be secondary effects due to hydrophobic adsorption, ionic interaction, or other interactions between the stationary phase and analyte. Gel permeation and non-ideal interactions in gel permeation are described more fully in Chapter 6. 

F. Matsumoto, K. Tokuda, and T. Ohsaka, Electrogeneration of superoxide ion at mercury electrodes with a hydrophobic adsorption film in aqueous media. Electroanalysis. 8, 648-653 (1996). 

McLaughlin, S. and Harary, H. (1976). The hydrophobic adsorption of charged molecules to bilayer membranes a test of the applicability of the Stem equation,... 

Interface and colloid science has a very wide scope and depends on many branches of the physical sciences, including thermodynamics, kinetics, electrolyte and electrochemistry, and solid state chemistry. Throughout, this book explores one fundamental mechanism, the interaction of solutes with solid surfaces (adsorption and desorption). This interaction is characterized in terms of the chemical and physical properties of water, the solute, and the sorbent. Two basic processes in the reaction of solutes with natural surfaces are 1) the formation of coordinative bonds (surface complexation), and 2) hydrophobic adsorption, driven by the incompatibility of the nonpolar compounds with water (and not by the attraction of the compounds to the particulate surface). Both processes need to be understood to explain many processes in natural systems and to derive rate laws for geochemical processes. 

The appeareance of maxima on the adsorption isotherms and decrease in flotability can be explained by the hypothesis that in the presence of micelles no adsorption layer of the surfactant can be formed, the character of which corresponds to the equilibrium state only with monomers (sufficiently hydrophobic adsorption layer). Due to a heterogeneity of forces acting at the surfactant ion mineral interface it can be assumed that at concentrations S CMC some of the molecules will be bound much more firmly in a three-dimensional micelle than in... 

A wide range of different supports for hydrophobic adsorption of enzymes is commercially available. Hydrophobic polymers are the most frequently used and they are typically based on acrylic, divinylbenzene-styrene copolymers or propylene polymers,... 

Introduction of a suppression device between the column and the detector can be expected to cause some degree of peak broadening due to diffusional effects. The shape of the analyte band will also be influenced by hydrophobic adsorption effects, especially when the adsorption and desorption processes are slow. Examination of peak shapes and analyte losses can therefore provide important insight into the use of suppressors with organic analytes which are weakly acidic or weakly basic. It can be expected that peak area recovery rates after suppression are governed by a combination of hydrophobic interactions with the suppressor and permeation through the membranes with the balance between these mechanisms being determined by eluent composition, suppression conditions and analyte properties. 

A means to avoid such tedious optimization can be envisaged by employing stoichiometric monomers to develop strong interactions with the template as mentioned above. The other way is to incorporate hydrophilic comonomers (2-hydroxyethyl methacrylate (HEMA), acrylamide) or cross-linkers (pentaerythri-toltriacrylate, methylene bisacrylamide) in the polymer. This results in an increase of the hydrophilicity of the polymer. Indeed, the use of HEMA for a MIP directed towards the anesthetic bupivacaine resulted in high imprinting factors due to reduced non-specific hydrophobic adsorption in aqueous buffer. This was not the case when HEMA was omitted from the polymerization mixture [27]. These conditions were exploited for the direct and selective extraction of bupivacaine from blood plasma samples. 

Hydrophobic adsorption to sediment particles appears to retard reduction of organic contaminants in anaerobic sediment slurries, so a quantitative kinetic model has been proposed that involves two types of "sites"(168-170),... 

The supernatant was subjected to fractional precipitation with ammonium sulfate (step 5) and then with acetone (step 6). PTTH was recovered in the precipitates with 35-55% acetone, while bombyxins were recovered with 55-75% acetone. The 35-55% acetone precipitates were subsequently purified through five steps of conventional chromatography gel filtration on Sephadex G-50 with 0.5M Tris-HCl (pH 8.5) (step 7), anion exchange on DEAE-Sepharose C1-6B with 0.2M sodium acetate (pH 5.2)(step 8), cation exchange on CM-Sepharose C1-6B 0.1-0.5M NaCl in 0.05M sodium acetate (pH 5.2) (step 9), Hydrophobic adsorption on Octyl-Sepharose C1-4B with 4M ammonium acetate, 0.2M ammonium acetate and 40% acetonitrile in 0.2M ammonium acetate (step 10) and gel filtration on Sephadex G-75 with O.OIM phosphate buffer containing 0.2M NaCl and 2% butanol (step 11). 

Carbon colloid Mitomycin C, Aclarubicin Hydrophobic adsorption... 

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