Analytical separations are widely distributed over all fields of chemistry now applied method of analyzing a compound has some deficiencies. But here we discuss the most widely used technique Chromatography.
First, we will discuss the history of chromatography:
In Ancient times Chromatography was used for the separation of color compounds such as plant pigments Different colored inks. As plants contain different types of chlorophyll’s they are separated in the best way by the use of chromatography.
Discovery of chromatography:
Initially, chromatography was used for the separation of colored compounds and herbal components. So chromatography was discovered by M.S in 1903 .he used plant pigments for the separation originally M.S was a Russian botanist.
Importance of Chromatography :
Chromatography is unique which has won two noble prizes. More than 60% of separations are done by the use of this technique. Mostly organic or inorganic compounds are also separated. Homogeneous mixtures are also well separated by applying this technique. It is also used for the identification of compounds either compound is solid or liquid.
Types of chromatography
Chromatography can be classified in to for main types :
- Liquid chromatography
- Gas chromatography
- Thin-layer chromatography
- Paper chromatography
- Chromatography can be further classified into following main types:
- ion-exchange chromatography
- Gel chromatography
- High -performance liquid chromatography
Before discussing of these powerful tools of an analyst or a scientist we have should have a short look on
Important terms of chromatography:
Chromatography is although a dramatic technique and works on the following principle which mainly consists of the following two phases:
- Mobile phase(Moving Phase )
This phase always moves over the stationary phases and often a solvent.
- Stationary phase(Non-moving phase)
This phase is found in a solute form and works with the mobile phase.
All of these use full & modern branches of chromatography are briefly discussed below:
Detailed & brief explanation of-some high lighted branches have the following technical use & are of great importance in all fields of chemistry especially in analytical chemistry:
In this type of chromatography mobile phase is always a solvent.
General Mechanism of Liquid -Liquid chromatography:
Solute distributes itself among two phases depending on their partition coefficients.
Types of Liquid chromatography:
there are the following types of liquid chromatography:
- liquid-liquid chromatography
- Liquid solid chromatography
- Liquid chromatography comprises two sub-phases based on their types:
- Normal phase chromatography
- Reverse-phase chromatography
Both phases are discussed according to the polarities of the mobile phase and stationary phase
Normal phase chromatography:
In this type stationary phase is always polar and the mobile phase is always non-polar.
So in this case, if silica is used in the place of the stationary phase than this phase is also called as normal phase chromatography.
in this type of chromatography mobile phase is always a polar component and stationary phase is always a non-polar.
Liquid -solid chromatography is mainly done in a column. Liquid solid column chromatography is most widely applicable and use full technique.
General mechanism of liquid column chromatography is given as follows:
Components are being separated within the mobile phase along the stationary phase .If sample components are colored than they can be seen in the forms of bands otherwise another technique HPLC is used for further process.
Another interesting information is that first phenomena of chromatography was observed in the form of liquid solid (column chromatography) chromatography.
Discovery of gas chromatography
Gas chromatography was discovered by JAMES & MARTIN in 1952 .
Gas chromatography can be defined as follows
Gas chromatography is such a technique in which separation is done on the process of partition between two immiscible phases:
Gaseous mobile phase (carrier gas) Stationary solid (immobilized liquid phase)
Carrier gas is kept in a cylinder with pressure or in a gas generating cylinder. Types of a carrier gas mainly effects on efficiency of a column.
Primary components of gas chromatography
Primary components of gas chromatography scheme are given as follows:
- Carrier gas system
- Sample injection method
Applications of gas chromatography:
Gas chromatography is widely accepted application in the field of analytical chemistry:
Complex mixtures can be separated by the application of this technique.
This is considered as a micro technique even a little quantity of sample can be tested with the help of gas chromatography.
Multifaceted and rapid:
As compared to other chromatographic technique gas chromatography is multifaceted and rapid action technique. Gas chromatography is also used for the separation of vitamins also.
Thin layer chromatography was discovered by lazmailov and Shraiber in era of 1938 by the use of plant extract. They used an adsorbent layer on a microscopic slide by the process of spotting the slides and further passed them from drying process.
Principle of Thin layer Chromatography:
Thin layer chromatography works in the process of adsorption. In this technique two phases are used on the base of different solubility. Components which have stronger interaction with the stationary phase moves at a slower speed.
The components having less affinity with the stationary phase move at a faster rate.
Applications of Thin layer chromatography:
Thin layer chromatography is used for the identification of substances.
This dramatic technique is also used for the test that either a compound is pure or not.
This method of chromatography is also a quick & fast method.
Amount of material:
The required amount of material in this technique is very small amount .placement of separated components:
Separated compounds are seen on the stationary phase in this process.
Discovery of paper chromatography:
Paper chromatography was discovered by two British biochemists Archer John Porter Martin (1910) and Richard Laurence Millington Synge (1914). In era of 1941 Martin and Synge Start working together on proteins, which are made up of many amino acids.
In paper chromatography cellulose is use as a support as a stationary phase.
Mobile phase consists of a soluble solvent or fluid.
Applications of paper chromatography:
Paper chromatography has following interesting applications:
For DNA & RNA:
It is used for the sequencing of DNA & RNA .
Main tool of analytical chemistry:
Paper chromatography is used on a larger scale for qualitative tool in analytical chemistry .
Paper chromatography is also used for the separation of impurities in drugs.
Use in different fields:
This interesting branch of chromatography can also be applied in the field of both organic and in-organic compounds.