What is chromatography?
The chromatography is a method of separating mixtures complex widely used along different branches of science. There are four types of chromatography, Paper chromatography, Gas chromatography, Liquid chromatography & Thin layer chromatography. It uses a set of techniques based on the principle of selective retention to separate the components of a mixture in a high state of purity or to identify them in a mixture and determine their exact proportion.
- Uses and Applications
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Adsorption ( not absorption ) is the coefficient of adhesion of the mixture to the surface of the support, and according to the difference in reaction rates of the components of the mixture, they can be effectively separated or their percentage can be measured in any case of concentration.
This separation process occurs in two phases:
- Static phase. The mixture is applied to specific support and prepared for measurement.
- Mobile phase. Another substance is moved on the support, to allow its reaction with the components of the mixture and that the difference in the reaction speed separates them.
In this way, some substances will tend to move and others to remain, according to their respective natures. This can be carried out using aesthetic and mobile phases of different conditions: liquid, solid and gaseous.
What are the main types of chromatography?
There are different types of chromatography techniques, that are classified according to their bed shape, that is, whether they are in their physical state in their mobile phase and the separation mechanisms.
- Column chromatography
- Paper chromatography
- Thin-layer chromatography
- High-resolution liquid chromatography.
It is the provident application of chromatography. It is used to achieve completely pure chemical compounds from a mixture of elements at a level of micrograms to kilograms using large industrial columns. The basic provident chromatography column is a glass tube with a diameter of 5 to 50 mm and a height of 50 cm to 1 m with a key on the bottom.
The solution is prepared with the permanent powder phase and then carefully spread on the column. Great care must be taken to prevent the production of air bubbles. A mixture of the organic material stirs over the stationary phase.
The main layer is generally covered with a small sand, cotton or wool chapel of the same glass to protect the shape of that organic layer, then it is slowly passed through its column to advance the organic material. Usually a round elution tank or a separating funnel is created taking the form of a stopper.
It is an analytical method used to identify and separate mixtures that are mainly painted with strong pigments. This process can also be used in secondary or elementary schools in laboratory ink experiments. This technique has been largely replaced by thin layer chromatography, however this method remains an effective teaching tool.
Bidirectional paper chromatography, known as two-dimensional chromatography, involves the use of two solvents and at the same time applying a rotation of the paper at 90 ° between them. This is advantageous to achieve the separation of complex mixtures of similar elements, a particular example is the separation of amino acids.
Thin Layer Chromatography
Thin Layer Chromatography (TLC) is a chromatography method that is effective in separating organic elements. It involves a stationary phase that lies in a very thin layer of the absorbent material, usually aluminum oxide, silica gel, or cellulose paralyzed on a completely flat inert strut sheet. The liquid phase lies in obtaining an exact solution to separate an appropriate solvent in attracted through a plate by fine action, managing to separate the experimental solution.
High-resolution liquid chromatography
High-Performance Liquid Chromatography (HPLC) is a type of column chromatography used daily in biochemistry and analytical chemistry. It is also sometimes known as high-pressure liquid chromatography and is used to separate the elements of a mixture by using a variety of chemical interactions between the substance being analyzed and the chromatography column.
In this type the analysis is forced through the column in its stationary phase usually the tube is full of small circular particles with certain chemistry on the surface pumping a liquid under high pressure through the column.
See also: Examples of Mixtures
Examples of chromatography
- Pour wine on a white tablecloth. When the wine dries in contact with the air, the various substances that compose it will dye the fabric white in a different color, thus allowing them to be identified when it would normally be impossible.
- In blood tests . Chromatography of blood samples is often carried out in order to separate and identify substances contained in it , normally imperceptible, from the color they reflect on a support or subjected to a specific light. Such is the case of a specific drug or substance, such as alcohol.
- In a urine test . Urine, even more than blood, is a mixture of various compounds, the presence or absence of which reveals how the body works. Therefore, a chromatographic separation can be performed to look for unusual residues , such as blood, salts, glucose, or drugs.
- Crime scene review . As in the movies: fabrics, fibers, tissues or other supports are taken to observe the separation by adherence of different substances , such as semen or blood, which at first glance could go unnoticed.
- Food sanitary checks . Since the reaction of foods to being subjected to a chromatographic spectrum is known, it can be seen if there is any type of improper substance or product of microbial agents in them from a small sample .
- Verification of contamination levels . Whether in air or water, the reaction of dissolved and imperceptible substances can be measured from a small sample, using a specific support that allows distinguishing between the compounds , for example, allowing the water to dry.
- Complex microbiology tests . This technique is widely used to combat diseases such as Ebola, for example, since in this case it allows the distinction between the most and least effective antibodies against the deadly disease.
- Petrochemical applications. Chromatography is useful in the process of separating hydrocarbons from petroleum and transforming them into various refined materials, which have highly dissimilar and observable properties and adhesions.
- Fire checking. To determine whether or not they were provoked, chromatography of the residues is often used, to show the presence of unexpected substances whose reactivity is different from the rest, such as certain fossil fuels.
- To separate inks. Since the inks are composed of various pigments in a liquid medium, it is possible to separate these pigments by chromatography and to show the differences between each one. It is, in fact, a common experiment in explaining this technique, using colored markers for it.
- Radioactivity detection. Since radioactive elements have different emission rates and activities than ordinary matter, they can often be identified using this technique in the laboratory, exposing matter to substances that demonstrate a change in reaction rate.
- To determine the purity of a substance. In industry, high purity materials are often required, especially gases (whose volatility makes it difficult) and a mechanism to evaluate it is the chromatographic detection of residues of other substances, using a liquid static phase.
- Wine study. In the detection of monovarietal wines, chromatography is often used to determine if they are mixed with other strain, since these will have different characteristics that can be detected in the presence of a different static medium.
- Control of industrial spirits distillate. By means of gas chromatography, the basic quality components present in the liquor (ethanol, methanol, acetaldehyde, acetal, etc.) can be identified and quantified, thus allowing responsible administration of said compounds.
- Quality studies of olive oils. Chromatography is essential in the review and classification of olive oil, since it provides a study of the fatty profile, acidity and peroxide value present in the mixture.