What is Chromatography? Types of chromatography

Published on 29-Jun-2022

What is Chromatography?

According to UPAC, "Chromatography is a physical method of separation in which the components to be separated are distributed between two phases one if which stationary, while the other moves in a definite direction."
Chromatographic techniques have been more valuable in the separation and analysis of highly complex natures than any other and revolutionized the capabilities of analytical chemistry.
Russian scientist Tsweet reported the first time separating a mixture of the color compounds. The stationary phase may be either liquid or solid. On the other hand, the mobile step is either gas or liquid.


Different Types of Chromatography

1. Gas Chromatography(GC)
2. Liquid Chromatography(LC)

3. Column chromatography.

4. Ion-exchange chromatography.

5. Gel-permeation (molecular sieve) chromatography.

6. Affinity chromatography.

7. Paper chromatography.

8. Thin-layer chromatography.

9. Dye-ligand chromatography.

What is chromatography?


Gas Chromatography
Gas chromatography separates gaseous substances based on adsorption or partitioning in a stationary phase from a gas phase.
Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. The gaseous compounds being analyzed interact with the walls of the column, which is coated with a stationary phase

Liquid chromatography

Liquid chromatography includes techniques such as Size exclusion (separation based on molecular size). Ion exclusion (separation based on charge) & High-performance liquid chromatography(HPLC separation based on adsorption or partitioning liquid-liquid phase)
Thin-layer chromatography (TLC) is a planar form of LC.

Column chromatography

The column chromatography method is used to separate the components of a mixture. It is based on the varied speeds at which the various compounds in the mixture pass through the column. The compounds are put into a tube and then poured with a solvent.

The solvent moves down the column, separating the various components depending on their respective motion speeds. Column chromatography can purify a compound or isolate specific components from a mixture. It's frequently employed in drug research and forensic science.

The stationary phase used in column chromatography is usually silica gel or alumina. Depending on the nature of the combination, the mobile phase might be any number of solvents; methanol and acetone are popular solvents. Column chromatography begins with the stationary phase being packed into a column or tube, followed by the sample being suspended in a solvent that serves as the mobile phase.

The solvent is slowly poured into the column's top. Because various compounds have varying affinities for the stationary phase material, different compounds migrate at different speeds down the column as it percolates through the mixture. As a result, smaller, more polar molecules will move more quickly than bigger, less polar ones.

The type of column you employ is determined by what you're trying to separate from your mixture. Normal-phase or reversed-phase column chromatography can be used; the two procedures are quite similar.

Ion Exchange Chromatography


Ion-exchange chromatography is a form of chromatography in which analytes are separated according to their ion charge. Ion exchange is employed in this procedure to separate molecules by causing them to interact with oppositely charged ions in the column's distinct reservoirs, causing them to flow down at different rates. 

If the molecule of concern is positively charged, and the stationary phase is negatively charged then it refers to cation exchange chromatography. If the stationary phase is positively charged and the molecule negatively charged then it refers to anion exchange chromatography.
Normal Phase Chromatography
Molecules are separated in normal phase chromatography by interacting with positively charged ions, whereas molecules are separated in the reverse phase by interacting with negatively charged ions. The neutral charges of particles that do not have charges are unaffected.


Paper Chromatography


Paper chromatography is a method of separating and identifying the constituents of a mixture. It's based on the idea that different compounds in a mixture move through a stationary phase at different speeds. The stationary phase in paper chromatography is a piece of paper, and the mobile phase is a solvent.

The analyzed compound is dissolved in the solvent before being applied to the paper. The paper is then stacked vertically with one end immersed in the solvent. The compounds are carried up the paper by the solvent as it goes up the paper.

The solvent separates the compounds into individual bands as it reaches the top of the paper, which can be identified by their color and Rf values. Plant extracts, proteins, and amino acids are frequently analyzed using paper chromatography.

The simplicity, low cost, and portability of paper chromatography are all advantages. Paper chromatography can be carried out in a lab or on the go. It's also pretty quick, with results appearing in minutes.

The poor resolution of paper chromatography, as well as the fact that it can only test a small number of substances at a time, are also limitations. Other analytical methods, such as gas chromatography or high-performance liquid chromatography, are more sensitive than paper chromatography.

Thin-layer chromatography

TLC stands for thin-layer chromatography, and it is a scientific method for separating distinct chemicals in a mixture. It works by enabling chemicals to travel through a thin sheet of paper coated with a specific material (known as the stationary phase).

The various chemicals in the combination will then travel at various rates, finally separating into bands on the paper. Thin-layer chromatography may be used to determine the relative quantities of various chemicals in a mixture.

It's a simple and quick procedure that can yield reasonably precise results. Thin-layer chromatography is frequently employed in forensic research, but it may also be used to examine plant extracts and foods.

 

More About Gas Chromatography

During World War II, James Bryant Conant and his colleagues at Harvard University invented gas chromatography. Because it separated a large number of molecules at once, gas chromatography boosted the quantity of information that could be gathered about a sample.

Gas chromatography also enables scientists to investigate samples that were previously too complex for conventional methods to handle, such as combinations comprising hundreds of different substances.

Gas chromatography was first used commercially in 1950 to evaluate some petroleum products, but it has since grown in popularity due to its ability to quickly separate a wide range of compounds.

Mass spectrometry, another technique for identifying the compounds in a sample, is frequently used with gas chromatography. For studying samples, gas chromatography/mass spectrometry (GC/MS) is an even more powerful tool. The analytes in a gas chromatograph are transported through the column using helium gas rather than air.

During World War II, while working on the Manhattan Project at Harvard University, James Bryant Conant invented gas chromatography.

He was able to separate thousands of substances at once using gas chromatography, which boosted the quantity of information he could collect about a sample.

One of the most difficult challenges in the creation of Gas chromatography was devising an efficient method for vaporizing samples so that they could pass through the stationary phase without being examined.

Gas chromatography was originally used commercially in 1950 to evaluate petroleum products, but it has since grown in popularity due to its ability to quickly separate a wide range of compounds.

Gas chromatography gained popularity after it was included in Gas chromatography/mass spectrometry (GC/MS), a technique that combines gas chromatography and mass spectrometry.

GC/MS is a more powerful instrument for evaluating samples than gas chromatography since it can detect individual chemical compounds rather than just the overall number of chemicals present.

The analytes in a gas chromatograph are transported through the column using helium gas rather than air. This is due to the fact that helium has a low viscosity and does not react with other substances.

 

What is Chromatography

The following topics will be added later.

  • affinity chromatography
  • immobilized metal affinity chromatography
  • gel permeation chromatography
  • chromatographic technique
  • stationary and mobile phases
  • separation technique
  • hydrophobic interaction chromatography
  • nucleic acids
  • partition chromatography
  • gas-liquid chromatography
  • ion chromatography
  • size exclusion chromatography
  • basic principle
  • organic solvent
  • chemical analysis
  • polar solvent
  • plant pigments
  • quantitative analysis

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