What Is Chromatography Definition Principle Types and Real Life Applications
We all know that a mixture is a combination of different elements or compounds. These elements are mixed uniformly and cannot be separated normally. Then how can we separate the elements of a mixture? Chromatography is a physical method of separation of different components of a mixture.
In this article, we are going to understand what is chromatography, types of chromatography, how can chromatography be used to separate mixtures, and how two dimensional chromatography is used for separating mixtures.
What is Chromatography?
Chromatography is a physical method of separation of different components of a mixture. In chromatography, the components to be separated are distributed between two phases, one of which is stationary while the other moves in a definite direction.
Types of Chromatography
On the basis of phases of separation of elements of a mixture, chromatography is divided into the following categories:
Column Chromatography - In column chromatography, mobile phase flows through the packed column.
Thin Layer Chromatography - In thin layer chromatography, the mobile part moves by capillary action.
Partition Chromatography - In partition chromatography, the stationary part is thin film of liquid adsorbable on an essentially inert support.
Paper Chromatography - Paper chromatography is an example of partition chromatography within which liquid present within the pores of paper is stationary phase and a few other liquid is movable part.
Absorption Chromatography - In adsorption chromatography, the stationary part could be a finely divided solid adsorbent and the mobile part is typically a liquid.
How Can Chromatography Be Used to Separate Mixtures?
The most widely used methodology of chromatography is paper chromatography. Chromatography separates components in a mixture according to their solubility within the mobile part and their absorbance to the stationary part. The mobile phase is the part of the chromatography set up that moves; the stationary part is the part of the set up that does not move.
Components that are more soluble within the mobile phase, i.e. adsorb less well to the stationary part, will move through the chromatography set up quicker as a result of there are fewer interactions with the stationary section to slow the component down. These components are going to be observed initially at the end point. Components that adsorb more powerfully to the stationary part have more interactions with the stationary part to block the movement of the component. These parts will be observed last at the end point.
Two Dimensional Chromatography
Two dimensional chromatography is used for separating mixtures. The combination of various separation techniques into one experiment (multi-dimensional chromatography; additionally known as 2D chromatography, orthogonal chromatography and cross-fractionation) permits for tackling the core of restricted chromatographic resolution by vastly improving the peak capability. This is specifically vital for the analysis of advanced polymeric materials.
In 2-dimensional chromatography, the sample is fractionated in a first dimension by one structural parameter and the fractions are collected. These fractions are then afterwards separated in a second chromatographic experiment separating according to a second structural feature.
2D Paper Chromatography
Two dimensional chromatography could be an advanced setup that is employed to separate complex mixtures.
The solvent is placed at the bottom of the tank and also the filter paper saturated with the stationary part is then kept within the tank. The development occurs upwards but very slowly because it's against gravity, additionally, as the compound could be a complex one.
After a few hours, the filter paper is turned 90 degree clockwise and also the tank is filled with a different kind of solvent. If there's no pronounced separation then development proceeds to the “c” stage.
Again the filter paper is turned ninety degrees clockwise and another solvent is used. This results in a satisfactory separation.
Although this may take some time, this allows a high degree of separation.
Interesting Facts
Chromatography is helpful in determining the antibodies that fight numerous diseases. Scientists used chromatography in the fight against the Ebola virus, responsible for over 11,000 deaths. The process was used to resolve which antibodies are the most effective at neutralising the deadly virus.
Chromatography is additionally used to facilitate catching criminals. In line with programs like CSI, gas chromatography (GC) is employed to research blood and fabric samples, helping to identify criminals and bring them to justice.
Conclusion
Chromatography is a physical method of separation of different components of a mixture. In chromatography, the components to be separated are distributed between two phases, one of which is stationary while the other moves in a definite direction. On the basis of phases of separation of elements of a mixture, chromatography is divided into the five different categories. Two dimensional chromatography is used for separating mixtures.
FAQs on Chromatography in Chemistry Principles Types and Applications
1. What is chromatography in chemistry?
Chromatography is a separation technique used to separate components of a mixture based on their different interactions with a stationary phase and a mobile phase. In chromatography:
- The stationary phase is a solid or liquid that remains fixed in place.
- The mobile phase is a liquid or gas that moves through the stationary phase.
- Components separate because they travel at different speeds depending on their adsorption, solubility, or affinity.
2. What are the main types of chromatography?
The main types of chromatography are classified based on the physical state of the mobile phase and separation mechanism. Common types include:
- Paper chromatography – uses paper as the stationary phase.
- Thin-layer chromatography (TLC) – uses a thin layer of silica or alumina.
- Column chromatography – uses a packed column with solid adsorbent.
- Gas chromatography (GC) – uses a gas mobile phase.
- High-performance liquid chromatography (HPLC) – uses high-pressure liquid mobile phase.
3. How does paper chromatography work?
Paper chromatography works by separating substances based on their different solubilities between a solvent (mobile phase) and water trapped in the paper (stationary phase). The process involves:
- Placing a small spot of the mixture near the base of the paper.
- Standing the paper in a solvent without submerging the spot.
- Allowing the solvent to rise by capillary action.
- Components move at different rates depending on their solubility and affinity.
4. What is the Rf value in chromatography?
The Rf value (retention factor) is the ratio of the distance travelled by a substance to the distance travelled by the solvent front in chromatography. It is calculated using:
- Rf = (Distance travelled by solute) / (Distance travelled by solvent front)
- Rf values range between 0 and 1.
- It is characteristic for a compound under fixed conditions.
- Used for identifying unknown substances by comparison.
5. What is the difference between adsorption and partition chromatography?
The difference between adsorption chromatography and partition chromatography lies in the separation mechanism.
- Adsorption chromatography: separation occurs due to different degrees of adsorption onto a solid stationary phase (e.g., silica gel).
- Partition chromatography: separation occurs due to different solubilities between two liquid phases (one stationary, one mobile).
6. What is the principle of gas chromatography?
Gas chromatography (GC) separates volatile compounds based on their different distribution between a gaseous mobile phase and a liquid or solid stationary phase. The principle involves:
- A carrier gas (e.g., helium or nitrogen) as the mobile phase.
- A column coated with stationary phase.
- Compounds vaporize and travel at different speeds.
7. What is the difference between GC and HPLC?
The main difference between gas chromatography (GC) and high-performance liquid chromatography (HPLC) is the type of mobile phase used.
- GC: uses a gas mobile phase; suitable for volatile and thermally stable compounds.
- HPLC: uses a liquid mobile phase under high pressure; suitable for non-volatile or thermally unstable compounds.
8. What factors affect separation in chromatography?
Separation in chromatography is affected by factors that influence interactions between solute, stationary phase, and mobile phase. Key factors include:
- Polarity of solvent and stationary phase.
- Temperature (especially in GC).
- Flow rate of the mobile phase.
- Surface area of the stationary phase.
- Nature and concentration of the sample.
9. What is a chromatogram?
A chromatogram is a graphical record of detector response versus time or volume in chromatography. In a chromatogram:
- Each peak represents a separated component.
- The retention time identifies the compound.
- The peak area is proportional to concentration.
10. What are the applications of chromatography?
Chromatography is used for separating, identifying, and purifying chemical substances in laboratories and industries. Major applications include:
- Drug testing and pharmaceutical analysis.
- Forensic analysis of inks, blood, and toxins.
- Food analysis for additives and contaminants.
- Environmental testing for pollutants.
- Biochemical purification of proteins and amino acids.
