Surface charge, influencing factors

Factors known to influence the clearance of drugs from interstitial sites, following extravasation or parenteral interstitial or transepithelial administration, include size and surface characteristics of particles, formulation medium, the composition and pH of the interstitial fluid, and disease within the interstitium. Studies indicate that soluble macromolecules smaller than 30 nm can enter the lymphatic system, whereas particulate materials larger than 50 nm are retained in the interstitial sites and serve as a sustained-release depot. The use of lipids or an oil in a formulation and the presence of a negative surface charge all appear to... 

Particles may be trapped on the biofilm surface or in voids of the biofilm where any organics may be hydrolyzed and further take part in the transformation processes. A number of factors influence adsorption and desorption of particles, such as particle size, surface charge, pH, etc., as well as biofilm surface properties and bulk water flow pattern. Studies of model biofilms have shown that water flows into the biofilm in small channels, making the prediction of transport of particles as well as soluble compounds complex (Norsker et al., 1995). 

Statistical mechanics was originally formulated to describe the properties of systems of identical particles such as atoms or small molecules. However, many materials of industrial and commercial importance do not fit neatly into this framework. For example, the particles in a colloidal suspension are never strictly identical to one another, but have a range of radii (and possibly surface charges, shapes, etc.). This dependence of the particle properties on one or more continuous parameters is known as polydispersity. One can regard a polydisperse fluid as a mixture of an infinite number of distinct particle species. If we label each species according to the value of its polydisperse attribute, a, the state of a polydisperse system entails specification of a density distribution p(a), rather than a finite number of density variables. It is usual to identify two distinct types of polydispersity variable and fixed. Variable polydispersity pertains to systems such as ionic micelles or oil-water emulsions, where the degree of polydispersity (as measured by the form of p(a)) can change under the influence of external factors. A more common situation is fixed polydispersity, appropriate for the description of systems such as colloidal dispersions, liquid crystals, and polymers. Here the form of p(cr) is determined by the synthesis of the fluid. 

Diffuse layer metal retention and outer sphere complex formation involve electrostatic attractive forces, which are characteristically weaker than co-ordinative interactions leading to inner sphere surface complex formation. A number of factors influence metal interactions with surfaces, including the chemical composition of the surface, surface charge, and the nature and speciation of the metal ion. The importance of the pH of the aqueous phase in these interactions will be discussed further in Section 3.2.4.1. 

In addition to these chemical reactions described above, many physical parameters need to be considered as well in terms of post-CMP cleaning. Extensive investigations have been conducted on the correlations between post-CMP cleaning efficiency and relevant physical forces such as the van der Waals force, electrostatic force, particle adhesion, chemical adsorption, surface charge modification, and wettability. It is expected that these factors strongly influence the particle-removal capability of post-CMP cleaning solution. 

---