What Is a Colloid Solution?

Colloidal solution refers to a solution formed by dispersing a solid particle drug or a polymer compound of a certain size in a solvent. The particle size of the dispersion system is generally between 1 and 100 nanometers. Most of the dispersion medium is water, and a few are non-aqueous solvents. Solid particles are dispersed in the solvent as multi-molecular aggregates (colloid particles) to form a heterogeneous heterogeneous dispersion system (lyophobic gum). The polymer compounds are dispersed in the solvent as a single molecule to form a single-phase uniform dispersion system. gum). This type of solution has its unique properties, which is different from low-molecular dispersion systemstrue solutions (dispersed phase particles smaller than 1 nanometer) and coarse dispersion systems (dispersed phase particles larger than 100 nanometers). Colloidal solutions are widely used in pharmacy, especially animal and plant drugs are more closely related to colloidal solutions in the preparation process.

Colloidal solution refers to a certain size of solid particles of medicine or

Colloid Press

Understanding and utilizing colloidal properties is important for the preparation of stable colloidal solution-type agents and for the processes used as other dosage forms. Such as protein-containing products of salting out and dialysis purification, and ethanol precipitation commonly used in Chinese herbal medicine injection to remove impurities, are all related to colloidal properties. Because it is difficult to distinguish clearly between the properties of the solution and the polymer solution, the characteristics of the colloidal solution are described as follows:

Colloid size

Between the true solution and the coarse dispersion system, the colloid bath is different from the true solution. It has a certain viscosity, and the diffusion speed of its colloidal particles is small. It can pass through the filter paper but cannot pass through the semi-permeable membrane, and has a small effect on the boiling point of the solution, the decrease of the freezing point, the decrease of the vapor pressure and the osmotic pressure. Due to this characteristic, dialysis and electrodialysis can be used to purify colloids, and ultracentrifugation can be used to separate colloidal particles.

Brown sports

Colloidal solutions are also different from coarsely dispersed systems. It belongs to a dynamic stable system and has a small settlement speed. Therefore, the colloidal solution can be kept for a long time without precipitation. However, in addition to strong Brownian motion in colloidal systems, due to the high degree of dispersion, the specific surface and surface energy of colloidal particles are large, and there is a spontaneous tendency of colloidal particles to reduce surface energy. Therefore, the colloidal solution is also a thermodynamically unstable system, and there is often agglomeration, which causes the colloidal solution to appear during long-term storage.

Positively charged colloid

Insoluble hydroxides (iron hydroxide, aluminum hydroxide, etc.), metal oxides, basic dyes (gentian violet, methylene blue, etc.), mercury bromide, heme, proteins in acidic solutions, etc.

Negatively charged colloid

Metals and metal sulfides,

The stability of the colloidal dispersion system mainly depends on the two factors of hydration and the charge of the colloidal particles. The stability of the hydrophilic gel and the hydrophobic gel are discussed separately as follows:

Hydrocolloid stability

It mainly depends on its strong solvation and hydration layer of colloidal particles. Because the hydration layer around the colloidal particles prevents the particles from agglomerating with each other, the thicker the hydration layer, the greater the stability. Therefore, all factors that can damage the hydrated layer of colloidal particles can cause the instability of the hydrocolloid. Such as adding a small amount to the hydrocolloid

Preparation of hydrocolloids ^[1]

1. Maintain normal colloid osmotic pressure in plasma.

2. Dilate plasma volume, increase blood volume, and increase blood pressure.

3. Improve microvascular circulation, can be used for anti-shock.

4. Increase the oxygen-carrying function of hemoglobin.

5. Low-molecular-weight sol has discrete agglutination of red blood cells, but cannot dissolve thrombus ^[2] .