accurate mass

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accurate mass

The mass of an ion of specified isotopic composition, which is calculated by summing the exact masses of the constituent atoms. The empirical formula of an ion can be deduced from the measured accurate mass of the ion if the ion mass is low enough to limit the number of formulaic possibilities and if the exact mass value is accurately known.
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References in periodicals archive ?
The group used data from ESO's Very Large Telescope (VLT) to measure the movement of stars or how fast the bodies were moving in the distant galaxy to underpin its exact mass.
The class of n-alkanes was identified by extracting chromatograms for the m/z 57.06983 (exact mass: 57.06988, error: -0.87 ppm), which corresponds to the common fragment C[H.sub.3]C[H.sub.2]C[H.sub.2]C[H.sub.2.sup.+].
Although situated nearly 13,000 light-years away, the celestial body has the exact mass as Earth and even orbits its star, in the same distance as our planet orbits the Sun.
In most cases, it is very difficult to discern the exact mass acting as a lead point.
Its ESIMS exhibited a pseudo molecular ion peak at m/z 691 [M+H] + and exact mass at m/z 691.3978 compatible with the molecular formula C38H59O11 (calcd.
This is where the limitation associated by the uncertainty principle of knowing simultaneously the exact mass and de cay time of a particle still remains.
The molecule's average mass was slightly higher than the exact mass due to the isotopic distribution, giving an M+1 ion one amu higher.
This new high-performance instrumentation, combined with exact mass libraries and screening tools from Agilent's MassHunter Workstation Software, provides scientists with a new level of confidence in library searching and a more efficient means to screen samples for both known and unknown compounds.
Note that the individual peaks in a mass spectrum are not some Gaussian curve shape as in most techniques, but exact mass value lines, and that the instrument resolution can be sufficient to differentiate even isotopic differences.
Compound 3D/2D, chemical properties/IUPAC name/part used/extracts/ pharmacology ent-labdane diterpenoids Andrographolide Neoandrographolide Chemical properties: Chemical properties: [C.sub.20][H.sub.30][O.sub.5] [C.sub.19][H.sun.28][O.sub.5] Exact mass: 350.21; Mof.
Engineers need to know the exact mass of fuel burned to calculate the specific impulse--a measure of propellant efficiency.