Saturday, May 2, 2020

What are the uses of chromatography?

Chromatography is the method used to isolate compounds or a sample mixture according to the relative affinity of each compound distributed amongst a stationary phase and a mobile phase. The compounds can be separated based on the different processes and the presence of characteristics, for example, hydrophobic groups present on the surface, size and shape, binding capacity with the stationary phase, and total charge. There are four main types of chromatography techniques are available such as partition chromatography, ion-exchange chromatography, adsorption chromatography, and size exclusion chromatography. Other chromatography methods are also available based on the stationary bed, such as high-performance liquid chromatography (HPLC), column chromatography, thin-layer chromatography (TLC), gas chromatography (GC), and paper chromatography, etc.
The chromatography has many applications in various fields which are mentioned below.
  • The chromatography is used in food processing for quality control.
  • Chromatography is used to check air quality and also the analysis of water samples.
  • It can use to determine the number of organic acids in foods that give significant information about food quality.
  • Chromatography is also used to determine the amount of drug present in blood samples, or urine.
  • It is used for the detection of contaminants (pesticides) or heavy metal in foods and food water.
  • It is mainly used in pharmaceuticals to verify the quality of the product or drug substance.
  • Chromatography is used in qualitative and quantitative analysis of molecules.
  • It is used to isolate solutions of dyes and pigments.
  • It is widely used in the forensic department to determine the alcohol or drug abuse.
  • Chromatography is also used in environmental applications, clinical diagnosis of diseases, petroleum industries, cosmetics, and herbal products, etc.
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Classification of chromatography based on the mechanism of separation

Chromatography is one of the widely used methods of separation in which the analytes to be separated are distributed between the stationary phase and mobile phase which travel on the stationary phase in a certain direction. The analytes of a sample mixture redistribute themselves between two phases by a process that may be partition, adsorption, ion exchange, or size exclusion. The stationary phase is either a solid or liquid and the mobile phase is either a liquid, gas, or a supercritical solution. The molecules are separated at different retention times as per affinity towards the stationary phase.
Below is the classification of chromatography based on the mechanism of separation.

Adsorption Chromatography:

Adsorption chromatography is the widely used chromatography technique for separation of components, it is working on the principle of adsorption in which the separation relies on the interaction of adsorbate with the adsorbent. The separation generally depends on the difference amongst the adsorption affinities of the molecules to the surface of an active solid. The three major types of adsorption chromatography are column chromatography, thin-layer chromatography (TLC), and gas-solid chromatography.

Partition Chromatography:

In this type of chromatographic technique, the compounds of the sample mixture distribute more probability in the two liquid phases caused by the difference in the partition coefficient. This relies on the molecules' distribution coefficient (Kd) and retention factor (K) using the mobile phase or liquid for stationary phases. The types of partition chromatography are the bonded-phase liquid chromatography and liquid-liquid chromatography.

Ion-Exchange Chromatography:

Ion-exchange chromatography is a kind of chromatography that separates components on the basis of charge. A column is used in the separation process that filled with a charged stationary phase on solid support, called an ion-exchange resin. The two types of ion chromatography are anion-exchange and cation-exchange

Exclusion chromatography:

Exclusion chromatography is also known as gel filtration or gel permeation chromatography, in this type of chromatography the separation of the analytes mainly depends on exclusion effects, that is the differences in molecular shape or size or charge. The mobile phase moves through a porous gel that separates the molecules according to their size.

Affinity Chromatography:

Affinity chromatography is a process in which the absorption separation based on the particular relationship between the compounds and the desired component in the ligand. It utilizes a particular interaction between a type of solute and another molecule, which is stable in the stationary phase.

Commonly asked questions on chromatography are as follows.

What is chromatography and its types?
Chromatography is a widely used separation technique to obtain pure compounds from sample mixtures. The 5 major types of chromatography include high-performance liquid chromatography, thin-layer chromatography, size exclusion chromatography, gas chromatography, and affinity chromatography.

What are the factors affecting separation in chromatography?
The flow rate of the mobile phase, the composition of the mobile phase, solvents used in the mobile phase, length of the column, nature, and composition of the stationary phase, the temperature of the column and working condition, pressure on the system, and structure, polarity, and size of the component is the factors that affecting the separation in chromatography

What is the factor responsible for the separation in column chromatography?
The differences of polarity between the solutes are responsible for the separation in column chromatography.


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What is the principle of chromatography technique?

Chromatography is a technique applicable to a wide variety of separation methods based on a solute distribution or partitioning between a mobile phase system (liquid or gas) and stationary phase (solid or liquid). The relative interaction of a molecule with the stationary phase and mobile phase is illustrated by the partition coefficient (k) which is the ratio of the molecule concentration in the stationary phase, to the concentration of the molecule in the mobile phase. The field of chromatography may be subdivided as per the specific methods used or the physicochemical principles used in the process of separation. The chromatographic processes developed using various combinations of the mobile phases and stationary phases. As different as the nature of interactions amongst the analytes and stationary or mobile phases, these processes can separate different types of solutes. The sample of different compounds is separated through the techniques at dissimilar rates. Such a difference in migration rates provides a separation as the mixture passes on the adsorptive materials. When there is more adsorption in the stationary phase, the component will gradually move and when there is less adsorption in the stationary phase, the component will move rapidly. Consequently, the disparity between the described factors determines the differential rates at which different components can travel through a stationary phase. The adsorption and solubility of an analyte can be changes by choosing the appropriate mobile phase and stationary phase.
All the techniques of chromatographic separations work according to the same basic principle. Each analyte of sample mixture interacts with other stationary phases in an attribute manner; hence they separate at different retention times. Since each analyte has a different affinity to the stationary phase and mobile phase, the analytes that have more interaction they will stay longer in contact with the stationary phase and thus will slowly elute. The high-performance liquid chromatography (HPLC), column chromatography, thin-layer chromatography (TLC), paper chromatography, and gas chromatography (GC) are the widely used techniques in chemistry.

Commonly asked questions on chromatography are as follows.

What is the definition of chromatography?
It is known as the technique of separating the individual mixture components based on their relative affinity to stationary and mobile phases. There are several types of chromatography; each has some kinds of mobile phase and stationary phase although the basic principle is always identical.

What are the 4 types of chromatography?
The partition chromatography, ion-exchange chromatography, molecular exclusion chromatography, and affinity chromatography are the major types of chromatography based on the mechanism of separation.

What are the 4 applications of chromatography?
Pharmaceutical applications, environmental applications, forensic applications, clinical diagnosis of diseases and disorder, petrochemical, analytical chemistry, biochemistry, quantitative & qualitative analysis are the major applications of chromatography.


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Thursday, April 23, 2020

What is the difference between LC and HPLC?

High-performance liquid chromatography (HPLC) is a widely used separation technique for the qualitative and quantitative analysis of compounds. HPLC, also known as high-pressure liquid chromatography, it is an advanced version of LC. In HPLC, we inject the sample solution through the syringe into the injector, the mobile phase carries it through a stationary phase (column) that isolates the molecule based on its affinity.HPLC has a wide range of applications, such as pharmaceuticals, forensics, clinical, and food analysis.
The major difference between traditional LC and HPLC is that the mobile phase of liquid chromatography moves by the gravity force while the mobile phase of HPLC flows through the high pressure that is created by the pump, which decreases the analysis time.

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