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Scan Mode and SIM ModeA quadrupole mass filter can be operated in a scan mode or select ion monitoring (SIM) mode.
In SIM, the mass filter is set to pass one selected m/z. This provides the greatest sensitivity and is used for quantitative applications. It is used when the analyst has prior knowledge of what ions to expect.
In scan mode, the mass filter is set to sequentially pass a range of masses. It has lower sensitivity because most of the ions strike the rods during the scan. For general unknowns, the selected mass may be at 100, then 101, then 102 and so on. This mode is used to collect spectra for interpretation or a library search.
IdentificationWhen a sample contains several components, they may be separated (in time) using chromatographic techniques.
After each component enters the mass spectrometer, its molecules are ionized, filtered, and detected to produce a unique mass spectrum.
The individual spectra are used to identify the components.
Quantitation Quantitative information also can be obtained from the mass spectral information. Typically, the quantitation is based on peak areas (or heights) from chromatographic data.
First, a known quantity of material(s)--a standard--is(are) analyzed. Next, an unknown quantity of sample is analyzed. The results are compared to calculate the amount of each component in the unknown.
ApplicationThe mass spectral data can be exported to any of the following:
Spreadsheets
Databases
Other types of reports
Other data systems
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