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GC-MS; Working Principle, Instrumentations, And Applications

Similar to so many other different techniques and instruments used in scientific analysis, GC-MS is one of the best instruments that we are using in our advanced scientific laboratories for different types of analysis.

Gas chromatography (GC) and Mass spectrometry (MS) are two techniques used in scientific analysis. GC-MS instrument can identify each component of a combination so you may determine…


What makes up a material?

How much of each component is present?


For smaller volatile and semi-volatile organic molecules like hydrocarbons, alcohols, and aromatics as well as for pesticides, steroids, fatty acids, and hormones, gas chromatography (GC) is the ideal separation technique.

As a result, this analytical method has many application areas and industry segments, particularly for food safety and environmental testing.

GC-MS separates complicated mixtures, measure analytes, find unknown peaks, and determine trace amounts of contamination when combined with the mass spectrometry (MS) detection capability.

To learn about the working of single beam spectrophotometer click here.


WORKING OF GC-MS

The GC-MS instrument uses the following two separate techniques:


Gas chromatography (GC)


GC-MS-Working-Principle-Instrumentations-And-Applications

The GC works on the chromatographic technique to separate volatile compounds that are both organic and inorganic.

Gas chromatography has two types on the basis of their stationary phase and liquid phase.


Gas-Liquid Chromatography (GLC)

Gas- Liquid chromatography works when Mobile Phase is a gas and Stationary Phase is a liquid, while Gas Solid Chromatography works when Solid Phase is a solid (GSC).

A high-resolution fused silica capillary column coated with Stationary Phase as a solid or nonvolatile liquid and enclosed in a temperature-controlled oven are the typical components of the GC.

The oven’s temperature is managed to enhance combination vaporization without decomposing and causing separation. The oven’s temperature is managed to facilitate mixture vaporization without decomposing and causing separation.

A sample solution is injected into the injection port, where the high temperature (up to 300 0 C) and low pressure (10 -4 -10 -7 torr) cause it to evaporate immediately. The sample (mixture) is then continuously added MP, which moves it through the column.

Elution is the name of this procedure. Depending on the affinity of the mixture components, the components physically interact to varied degrees with the SP and MP material as the sample passes through the column.

As a consequence, various chemicals will move through the capillary column at varying rates and leave the column after a certain retention period.

Depending on the concentration and sensitivity of a certain component, a signal is generated as the components in the mobile phase pass through the column and reach the detector.

Depending on how many components are present in the sample, a plot of signal vs. time produces many peaks in a chromatogram.

You can also find these topics in the following analytical chemistry books


GC-MS-Working-Principle-Instrumentations-And-Applications

Fig. 2 illustrates the mixture’s five distinct components.


So from the height of the peak and the area under the peak of GC- Chromatogram, we can conclude the information about sample composition, retention time, and the quantity of the substance.

In general, the components will leave the column one by one by their retention times (the shorter the retention time faster will be the elution).

Yet, sometimes peak overlapping or peak broadening occurs as a result of less interaction with the gas phase (Mobile phase) and more interaction with the solid phase (Stationary Phase).


Instrumentation

The GC column, which is made up of nonpolar stationary phases such as dimethyl siloxanes, is often followed by a headspace or injector, which is in charge of injecting the material. The thickness of the stationary phases varies as well; the thin stationary phases are appropriate for analytes that volatilize at higher temperatures whereas the thick stationary phases are appropriate for compounds that volatilize at lower temperatures.

The detectors are used to find the analytes once they have been separated. There are several detectors, including electron capture detectors (ECD), thermal conductivity detectors, flame ionization detectors, and thermionic-specific detectors. Depending on the sort of material being studied, these detectors are employed in various ways.

In GC-MS, a distinctive device is attached that is in charge of moving the samples from the GC to the MS. Before ionization at the MS, this device maintains the phase of the sample and protects its integrity. The samples are again moved from one instrument to the next using an inert carrier gas.


Mass Spectrometry (MS)

In the GC-MS technique, GC separates a mixture and then creates “pure” fractions. Each component is then sent to the mass spectrometry, where mass separation in the ion analyzer, detection, and ionization and fragmentation in the ion source section occurs, respectively.

GCMS provides a wider sight of the identification of substances.

It separates different components of a substance by using mass spectra.


Principle of Mass Spectrometry (MS)

MS is a technique that studies how ionizing radiation affects molecules. It depends on the chemical processes that consume sample molecules during the formation of ionic and neutral species in the gaseous and ionic phases.

The process involves converting the material into gaseous ions, either with or without fragmentation, and then by identify them by their relative abundances and mass to charge ratios (m/z) (peak).


Instrumentation


GC-MS-Working-Principle-Instrumentations-And-Applications

Here are the four major components of mass spectrometry:

Ionizer:

Electrons bombard the sample. Between the cathode and the anode, these electrons travel. High-energy electrons knock electrons out of the sample as it travels through the electron stream between the cathode and anode, forming ions.

Accelerator:

Ions are positioned between a pair of charged parallel plates, and they are drawn to one plate and repelled by the other. By altering the charge on the plates, the acceleration speed may be controlled.

Deflector:

The magnetic field deflects ions according to their mass and charge. The least deflected ions are those that are heavy or have two or more positive charges. Ions deflect when they are light or have a single positive charge.

Detector:

The ions that have the right charge and mass go to the detector. The ion that strikes the detector helps to determine the mass-to-charge ratio.


GC-MS-Working-Principle-Instrumentations-And-Applications


Applications of GC-MS


GC-MS Applications in Water Monitoring and Analysis

  • GCMS separates and quantify Organic molecules up to the ppb level. As a result, this may help to check the total organic carbons (TOCs) in drinking water, which include pesticides, endocrine disruptors, chlorofluorocarbon compounds, protein, and radioactive materials. GC-MS analysis can analyze ultra-pure water in which very low levels of total organic carbon are present, with a typical resistivity of 18.2 M. cm, a very low TOC value of less than 2 ppb, and bacteria levels below 0.1 CFU/ml.


GC-MS Applications in Environmental Monitoring and Clean-up

  • For locating organic contaminants in the environment, GC-MS is the go-to technique. For some substances, such as some pesticides and herbicides, GC-MS is not sensitive enough; still, it is for the majority of organic assessments of environmental materials, including many important classes of pesticides, and it is extremely sensitive and effective.


GC-MS applications in Criminal Forensics

  • With the use of GC-MS, it is possible to link a criminal to a crime by analyzing the particles from a human body. GC-MS can analyze fire debris. Because samples typically contain immensely complicated matrices and findings used in court need to be very exact, GCMS/MS is particularly helpful in this situation.


GC-MS Applications in Law Enforcement

  • GC-MS replaces Drug-sniffing dogs to illegal drug detection. In forensic toxicology, GC-MS can identify drugs and/or poisons in biological samples from suspects, victims, or the deceased.


GCMS Applications in Sports Anti-Doping Analysis

  • In sports anti-doping labs, the primary instrument used to examine urine samples from athletes for the presence of illegal performance-enhancing substances, such as anabolic steroids, is GC-MS.


GC-MS Applications in Food and Fragrance Analysis

  • GC-MS is a simple technique for analyzing aromatic chemicals found in food and drink, including fatty acids, esters, aldehydes, alcohols, and terpenes. It can also detects Food contamination or rotting in food contents.


GC-MS Applications in Astrochemistry

  • Many GC-MS have already fled the planet. The Viking programme sent two people to Mars. Venus’ atmosphere was examined by Venera 11 and 12, as well as Pioneer Venus, using GC-MS. One GC-MS was successfully landed on Titan, Saturn’s biggest moon, by the Cassini-Huygens expedition. In 2014, the Rosetta mission examined the comet 67P/Churyumov-material Gerasimenko’s using a chiral GC-MS.


GC-MS Applications in Medicine

  • Drugs including anticonvulsants, anesthetics, antihistamines, sedative hypnotics, and anti-epileptic medications can all be found in bodily fluids that have undergone bioanalysis using GC-MS. Additionally, it aids in fatty acid profiling of microbes and the detection of contaminants and metabolites in serum.

  • Gas chromatography-mass spectrometry may now be used to identify dozens of congenital metabolic illnesses, known as “In born” abnormalities in metabolism. Even in urine with low concentrations, chemicals may be identified by GC-MS. By doing a urine test at birth based on GCMS and comparing the results to healthy conditions, it is now feasible to screen a baby for over 100 hereditary metabolic diseases.

  • The GC-MS measures metabolic activity together with the isotopic tagging of metabolic compounds. The majority of applications rely on the detection of 13C-12C ratios using an isotope ratio mass spectrometer (IRMS), an MS with a detector intended to measure a small number of specific ions and return data as ratios.


FAQ’s

Q#1 what is the basic principle of mass spectrometry?Q#1 what is the basic principle of mass spectrometry?

Multiple ions are produced from the material being studied by a mass spectrometer, which then separates them based on their unique mass-to-charge ratios (m/z) and reports the relative abundance of each ion type.

Q#2 what equipment does mass spectrometry use?

A device called a spectrometer is made to test the wavelengths of light over a wide range of the electromagnetic spectrum. This is often used for studying sample materials using spectroscopy. Through the sample, the incident light from the light source may be emitted, absorbed, or reflected.

Q#3 what is the basic principle of GC-MS?

The GC operates under the principle that heating a mixture will cause it to split into separate compounds. An inert gas is used to transport hot gases through a column (such as helium). The separated materials flow into the MS when they leave the column opening

Q#4 what are the major applications of GC-MS in Environmental monitoring?

For locating organic contaminants in the environment, GC-MS is used. For some substances, such as some pesticides and herbicides, GC-MS is not sensitive enough; nevertheless, for the majority of organic assessments of environmental materials, including many important classes of pesticides, it is extremely sensitive and effective. It is used to check the contaminants (heavy metals, pesticides, herbicides, etc.) present in different media of environment e.g. soil, water, etc.


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