Search results
Results from the WOW.Com Content Network
The accurate mass (more appropriately, the measured accurate mass [9]) is an experimentally determined mass that allows the elemental composition to be determined. [10] For molecules with mass below 200 Da, 5 ppm accuracy is often sufficient to uniquely determine the elemental composition. [11]
For example, the conversion factor between a mass fraction of 1 ppb and a mole fraction of 1 ppb is about 4.7 for the greenhouse gas CFC-11 in air (Molar mass of CFC-11 / Mean molar mass of air = 137.368 / 28.97 = 4.74). For volume fraction, the suffix "V" or "v" is sometimes appended to the parts-per notation (e.g. ppmV, ppbv, pptv).
Mass accuracy is usually measured in ppm or milli mass units. The mass range is the range of m/z amenable to analysis by a given analyzer. The linear dynamic range is the range over which ion signal is linear with analyte concentration.
Some mass spectrometrists use the definition that is similar to definitions used in some other fields of physics and chemistry. In this case, resolving power is defined as: R = M Δ M = r e s o l v i n g p o w e r {\displaystyle R={\cfrac {M}{\Delta M}}=\mathrm {resolving\ power} }
Universal Mass Calculator Freeware: UMC is programmed as a mass spectrometry tool to assist interpreting measurement results, mainly derived from molecular or quasi-molecular ions. It can be used for the calculation of: Mass deviation (mmu or ppm) of measured mass from given empirical formula; Mass differences of two empirical formulas
Suppose there are known concentrations of nickel in a set of calibration solutions: 0 ppm, 1.6 ppm, 3.2 ppm, 4.8 ppm, 6.4 ppm, and 8 ppm. Each solution also has 5 ppm yttrium to act as an internal standard. If these solutions are measured using ICP-OES, the intensity of the yttrium signal should be consistent across all solutions.
All of these instruments provide a high mass accuracy (<2–3 ppm with external calibrant and <1–2 ppm with internal), a high resolving power (up to 240,000 at m/z 400), a high dynamic range and high sensitivity.
In mass spectrometry the mass accuracy of a mass analyzer is often indicated in mu, even though a more correct unit would be mTh (millithomson) since mass spectrometers measure the mass-to-charge ratio, not the mass. [3] The relative mass accuracy is often indicated in ppm, even though this is no longer supported by the IUPAC green book which ...