Suspensions are heterogeneous mixtures that are studied in chemistry. Heterogeneous mixtures are those in which the particles that make them can be distinguished.
These are formed by one or more substances that are in solid state suspended in a liquid medium. To be a suspension and not a solution, the solid particles can not be soluble in the liquid medium.
The particles in the suspension should be larger than one micron in size. Some solutions prevent light from passing properly, even becoming opaque.
Suspensions can be separated into solid and liquid particles through decanting, filtration , Centrifugation or evaporation .
Once the suspension is made, some of the particles can be added to others, so if we want to keep the suspension, surfactants or dispersing agents are usually added to the liquid medium.
It is necessary to distinguish between suspensions, solutions and colloids. The solutions are homogeneous mixtures, where the solid particles are dispersed in the liquid medium by changing the atomic or ionic level. Colloids are heterogeneous mixtures where the solid particles are smaller in size to one micron.
In a suspension four phases can be distinguished. The first phase, is the solid phase or internal phase where the solid particles can not be divided into the suspension.
In the external phase, or also known as liquid phase, is where the solid particles are at rest in the liquid part.
In the surfactant part of the suspension the elements are not joined or added. And lastly, we can use stabilizers in the suspension to increase its solubility and prevent the particles from deteriorating. These stabilizers may be thickeners, antifreeze or preservatives.
Examples of suspensions
1-Fruit juice: these are suspensions as the fruit pulp floats in the liquid medium. If we only want to dispose of the liquid medium we must decant or filter the mixture.
2-Turbid water of the rivers: in this suspension the sediments that drag the river form the suspension.
3-Watercolors: are a suspension that is deposited in the paper where it filters the water and collects the color pigment
4-Powder medicines: to be kept in suspension and not deposited in the bottom must be stirred.
5-Exfoliating creams: where there are small particles forming solid grains in the cream to fulfill the function of exfoliation.
6-Milk: animal fat particles are in solution with water. Because they are less dense than the dispersant, they tend to stay on the surface over time
7-Paint: is a suspension of the color pigments in an aqueous or oily medium. If it does not shake, it may separate.
8-Sea water: In the area of the shore can be considered a suspension with particles of sand, although this suspension is of limited duration.
9-Salad dressings: they contain vegetable particles suspended in oil or vinegar, they have a viscous dispersant that keeps them in a state of rest.
10-Suspensions of injectable drugs: the drugs are in solution in a saline so that they can access the blood stream more easily.
Other examples of common suspensions
11-Water of horchata
12-Cocoa in milk or water
13-Moisturizing creams or face creams
14-Penicillin
15-Insulin
16-Amoxicillin (antibiotic)
17-Powder Makeup
18-Ash in a volcanic eruption
19-The lime slurry
20-Milk powder
Examples of pharmaceutical suspensions
Pharmaceutical suspensions are used when the drug is insoluble per se, in addition to being more stable in the form of a suspension or emulsion.
Once the drugs need to be controlled, when used in a suspension the rate of release of the active ingredient can be controlled.
And one of the biggest reasons to use suspended and injectable drugs is because patients do not tolerate the bad taste of the medication or its pill form
21-Antacid Suspensions (used as a stomach acid medicine) are suspensions of magnesium hydroxide or aluminum hydroxide. Medications like Mylanta or AciTip
22-Suspensions of corticosteroid drugs. Examples may include Diprospan, Scherin
23-Suspension of white clay (kaolin) as antidiarrheal methods
24-Suspensions of antiparasitic drugs. For example, Metronidazole suspensions
25-Suspensions for oral use, these suspensions are prepared mainly so that they do not need to be injected, but can be taken orally.
26-Optical suspensions, where the suspensions are prepared to be used inside the ears superficially.
27-Topical suspensions: they are prepared to use directly on the skin without being injected
28-Ophthalmic suspensions: are a suspension with a neutral ph specific for use in the eyes
29-Injectable Suspensions: These are the most widespread suspensions within the pharmaceutical field, where the drug is in suspension for intravenous injection.
30-Rectal suspensions: these are prepared to be used as a suppository rectally, usually through an enema.
References
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- COTTON, F. Albert Wilkinson, et al. Basic inorganic chemistry . Limusa, 1996.
- HIMMELBLAU, David M. Basic Principles and Calculations in Chemical Engineering . Pearson Education, 1997.
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