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What is Liquid Chromatography-Mass Spectrometry?

Remember an experiment that your high school science teacher asked you to do? It involved a marker, a piece of blotting paper and a glass of water. This is how it goes: if you draw a line with a marker on a blotting paper and dip it in a glass of water, the water runs into the paper, dissolves the ink, and prints the shades of the rainbow on the paper. What you would achieve from this experiment is a simplified model of Liquid Chromatography (LC).

This process is used in laboratories to separate the different components of a mixture, using a liquid medium. Taking the above mentioned experiment as an example, the mixture (here, ink from the marker), dissolves in a fluid (water in the glass), known as the mobile phase and as a result is spread over a second medium (the blotting paper), the stationary phase, which was originally holding the mixture. The purpose of this procedure is to separate the components of a mixture, sometimes as a process of extraction or purification, but in most cases, to study the different components. Although principally simple, this actually forms a fundamental technique in chemical analysis has important and yielding applications in various fields, like medicine, forensics, and geology, especially when it is used in combination with another chemical analysis tool, Mass Spectrometry (MS).

MS is used in laboratories to measure the mass-to-charge ratio of ions. The precursor under observation is bombarded with electrons, which break up the molecules or atoms of the sample into charged ions. These ions are then directed into an electric or a magnetic field, which deflects them. The final result is a spectrum with varying intensity of ions as a function of their mass-to-charge ratio. This spectrum can then be studied to identify the components of the sample atom or molecule, based on the amount of deflection of the ions on the plot.

Difference Between LC-MS and LC-MS/MS

Nowadays, LC-MS is being fast replaced with LC-MS/MS analysis, in which two mass analyzers are used in the same MS system. In LC-MS, often after fragmentation, some components of the sample might turn out to have the same molecular weight, in which case, they will produce the same ions. This confusion can be negated using LC-MS/MS tests because one MS filters the precursor ions and subsequently, bombards it with more electrons. The next MS detects these product ions, thus making the process foolproof.

Uses of LC-MS/MS

LC-MS/MS assay is used widely in pharmaceuticals. It is predominantly used to identify chemical or biochemical entities and is often used to detect chemicals in case of intoxication. It is also used to purify or extract components of a crude biochemical mixture, like lipids, alkaloids, and fatty acids. This method also helps monitor antibiotics, anti malarial, and other drugs.

All-in-all,  experienced scientists can conduct the tests to deliver accuracy and precision.

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