1. Explain the principles behind Gas Chromatography-Mass Spectrometry (GC-MS).
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Explanation:
Gas Chromatography Mass Spectrometry (GC/MS) Information
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Gas Chromatography Mass Spectrometry (GC-MS) Information
GC/MS targets small and volatile molecules
GC/MS is the analysis method of choice for smaller and volatile molecules such as benzenes, alcohols and aromatics, and simple molecules such as steroids, fatty acids, and hormones. It can also be applied towards the study of liquid, gaseous and solid samples.
There are many advantages to using GC/MS for compound analysis, including its ability to separate complex mixtures, to quantify analytes, and to determine trace levels of organic contamination.
GC/MS begins with the gas chromatograph, where the sample is volatized. This effectively vaporizes the sample (the gas phase) and separates its various components using a capillary column packed with a stationary (solid) phase. The compounds are propelled by an inert carrier gas such as argon, helium or nitrogen. As the components become separated, they elute from the column at different times, which is generally referred to as their retention times.
Once the components leave the GC column, they are ionized by the mass spectrometer using electron or chemical ionization sources. Ionized molecules are then accelerated through the instrument’s mass analyzer, which quite often is a quadrupole or ion trap. It is here that ions are separated based on their different mass-to-charge (m/z) ratios.
The final steps of the process involve ion detection and analysis, with compound peaks appearing as a function of their m/z ratios. Peak heights, meanwhile, are proportional to the quantity of the corresponding compound. A complex sample will produce several different peaks, and the final readout will be a mass spectrum. Using computer libraries of mass spectra for different compounds, researchers can identify and quantitate unknown compounds and analytes.
GC is the separation technique of choice for smaller and volatile molecules such as benzenes, alcohols and aromatics, and simple molecules such as steroids, fatty acids and hormones. It is widely used for chemical analysis, and especially for drug and environmental contamination testing. When combined with MS, GC/MS can be used in both full scan MS or select ion monitoring (SIM) mode to cover either a wide range of m/z ratios or to gather data for specific masses of interest, respectively.
Answer:
The GC works on the principle that a mixture will separate into individual substances when heated. The heated gases are carried through a column with an inert gas (such as helium). As the separated substances emerge from the column opening, they flow into the MS.
Explanation:
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