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Mass spectrometry software is used for data acquisition, analysis, ... It contains an isotope calculator and other features and on-line help. This program is a ...
Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample. [1] [2] This technique has two different applications in the earth and environmental sciences.
The monoisotopic mass is the sum of the masses of the atoms in a molecule using the unbound, ground-state, rest mass of the principal (most abundant) isotope for each element. [12] [5] The monoisotopic mass of a molecule or ion is the exact mass obtained using the principal isotopes. Monoisotopic mass is typically expressed in daltons.
Nominal mass is a term used in high level mass spectrometric discussions, it can be calculated using the mass number of the most abundant isotope of each atom, without regard for the mass defect. For example, when calculating the nominal mass of a molecule of nitrogen (N 2) and ethylene (C 2 H 4) it comes out as. N 2 (2*14)= 28 Da C 2 H 4
The name is an akronym resulting from this original purpose: Sum formula Identification by Ranking Isotope patterns Using mass Spectrometry. In 2008 the group introduced the concept of fragmentation trees [2] for identification of the molecular formula based on fragmentation mass spectrometry data, also called tandem MS or MS2 data.
Ion mobility spectrometry-mass spectrometry (IMS/MS or IMMS) is a technique where ions are first separated by drift time through some neutral gas under an applied electrical potential gradient before being introduced into a mass spectrometer. [43] Drift time is a measure of the collisional cross section relative to the charge of the ion.
Isotope peaks within a spectrum can help in structure elucidation. Compounds containing halogens (especially chlorine and bromine ) can produce very distinct isotope peaks. The mass spectrum of methylbromide has two prominent peaks of equal intensity at m/z 94 (M) and 96 (M+2) and then two more at 79 and 81 belonging to the bromine fragment.
Isotope dilution is almost exclusively employed with mass spectrometry in applications where high-accuracy is demanded. For example, all National Metrology Institutes rely significantly on isotope dilution when producing certified reference materials.
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