Colloid hydrophilic

An emulsifying agent generally produces such an emulsion that the liquid in which it is most soluble forms the external phase. Thus the alkali metal soaps and hydrophilic colloids produce O/W emulsions, oil-soluble resins the W/O type (see emulsion). 

All hydrophilic colloids possess some degree of protective action and gelatin, starch and casein are used commercially for this purpose. 

The colloidal particles can be crystalline or constitnte an amorphons agglomeration of individual molecnles. The definition also includes nonaggregated large macromolecules such as proteins. An arbitrary distinction is made between hydrophobic colloids (sols) and hydrophilic colloids (gels), which depends on the degree and type of interaction with the aqneons solvent. 

For suspensions primarily stabilized by a polymeric material, it is important to carefully consider the optimal pH value of the product since certain polymer properties, especially the rheological behavior, can strongly depend on the pH of the system. For example, the viscosity of hydrophilic colloids, such as xanthan gums and colloidal microcrystalline cellulose, is known to be somewhat pH- dependent. Most disperse systems are stable over a pH range of 4-10 but may flocculate under extreme pH conditions. Therefore, each dispersion should be examined for pH stability over an adequate storage period. Any... 

Hydrophilic colloids are colloidal particles that attract water molecules, whereas hydrophobic colloids are colloidal particles that repel water molecules. 

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. 

Bran, a grain milling waste product, and linseed (flaxseed) are both rich in cellulose. Other hydrophilic colloids derive from the seeds of Plantago species or karaya gum. Ingestion of hydrophilic gels for the prophylaxis of constipation usually entails a low risk of side effects. However, with low fluid intake in combination with a pathological bowel stenosis, mucilaginous viscous material could cause bowel occlusion (ileus). 

POOH Anderson]. W., S. Riddell-Mason, N. J. Gustafson, S. F. Smith, and M. Mackey. Cholesterol-lowering effects of psyllium-enriched cereal as an adjunct to a prudent diet in the treatment of mild to moderate hypercholesterolemia. Amer J Clin Nutr 1992 56(1) 93-98. Day, C. E. Activity of psyllium hydrophilic colloid for reducing serum cholesterol in sea quail fed diet supplemented with cholesterol. Artery 1991 18(3) 163-167. 

These contain natural or semisynthetic hydrophilic colloidal derivatives of cellulose. 

Modifications of monodisperse colloidal silica, of 10 or 500 nm in diameter, were carried out using trialkoxysilane-terminated polymer in a low polar solvent, such as acetone or 1,2-dimethoxyethane. without coagulation during the coupling reaction (35,37-42). In this modification, the hydrophobic polymer can be efficiently bound to hydrophilic colloidal silica surface. The reaction mechanism of the binding... 

Bulk-forming laxatives are indigestible, hydrophilic colloids that absorb water, forming a bulky, emollient gel that distends the colon and promotes peristalsis. Common preparations include natural plant products (psyllium, methylcellulose) and synthetic fibers (polycarbophil). Bacterial digestion of plant fibers within the colon may lead to increased bloating and flatus. 

We include certain excipients in a formulation specifically because they interact with the physiological fluids and the bodily functions in a certain way. For example, as discussed above, we include disintegrants in immediate release tablet and capsule formulations, because we know that when they encounter the aqueous environment of the stomach, they will cause the tablet or capsule to disintegrate and thereby aid dissolution of the API. Another example is the general case of hydrophilic colloid matrices used as prolonged release drug delivery systems. We know that when these materials contact the aqueous environment of the GIT they swell and create a diffusion barrier that slows the rate of dissolution of the dissolved drug. 

CA 67, 75047n(J967) [Gelled expl compns contg a Xanthomonas hydrophilic colloid mixed with aq soln of inorganic nitrate (such as AN) and borax are described. Xanthomonas is a hydrophilic, exocellular, high-mo 1-wt colloid prepd by culture fermentation by... 

Complex coacervation (3) can be induced in systems having two dispersed hydrophilic colloids of opposite electric charges. Neutralization of the overall positive charges on one of the colloids by the negative charge on the other is used to bring about separation of the polymer-rich complex coacervate phase. 

Often, a binding or adhesive granulating agent is required which may be added in solution or mixed with the tablet ingredients as a dry powder for subsequent activation by moisturing with an appropriate solvent. Many binders are hydrophilic colloids as, for example, polysaccharides (Table 5). 

When mixed with water, carboxymethylcellulose sodium [9004-324J makes a bulky hydrophilic colloid which is indigestible and nonabsorbable. It produces softening of formed stools within three days, but may cause fluid retention because of its sodium content. 

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