Talk:Resolving power (in mass spectrometry)
Kermit Murray?????????????? 01-30-2004 04:17 PM ET (US)
ASMS Terms and Definitions Poster has "mass resolving power - m/Dmx, where Dmx is the mass resolution "
Glen Gregory??????????????
Glen Gregory?????????????? 02-28-2004 01:33 AM ET (US)
It should be noted that since Resolving Power is dimensionless, a specified mass/charge value should always be referenced for a given Resolving Power, i.e.- 5,000 Resolving Power for m/z 500. This allows for extrapolation across a broad mass range, such as the over all range of the MS instrument.
Alternatively, to simplify (and unify) resolution designation for non magnetic-sector instruments (those which exhibit constant peak width?????????????????????????s, such as ion trap's, ToF's, QToF's, and triple quad's), a common terminology used is "FWHM" (full width at half mass). This is the width of a mass peak (in amu, profile mode), half way up the height of the peak. This leads to the definition of a Gaussian peak with a 1 amu width at 10% base line, or "unit" resolution, as having 0.7 amu "FWHM" resolution. 0.7 FWHM now becomes the "standard" reference. With this definition, (again on constant peak width instruments only, such as the ones listed above), the lower the FWHM value, the better the resolution, regardless of m/z.
ASMS Terms and Definitions Poster Entry
Resolution of the Confusion on Peak Separation
Mass resolving power and mass resolution have been used interchangeably throughout the literature, so the confusion surrounding their exact meaning is understandable. In his forthcoming book, "Guide to Mass Spectrometry," Ken Busch advocates definitions that are consistent these proposed terminologies for mass resolution and mass resolving power. In most disciplines, resolution is understood to be the smallest observable change in a quantity, whereas resolving power, i.e. the ability to distinguish two closely spaced quantities, is inversely proportional to resolution. Proposed definitions: mass resolution
the mass (actually, m/z) difference, ?????????????????mx that exists between two adjacent peaks in a mass spectrum that are of equal size and shape (Gaussian, Lorentzian, triangular) with a specified amount of overlap, where the subscript "x" denotes the overlap criterion (10% valley, Full Width at Half Height [FWHH], etc.) See Usage Note for mass resolving power and theoretical mass resolving power mass resolving power
m/?????????????????mx, where ?????????????????mx is the mass resolution
See Usage Note for theoretical mass resolving power
Usage note: Although the definition of mass resolution is contingent upon two adjacent, mass spectral peaks of equal size and shape, which is almost never the case experimentally, it is acceptable to calculate the mass resolving power or mass resolution from a single peak. An assumption is made about the peak shape, whereby the peak width at 5% height for a single peak would be approximately equivalent to the distance between the apexes of two peaks with a 10% valley between them. This assumption is not unreasonable for most common peak shapes encountered in mass spectrometry. Therefore, the mass resolving power that is obtained by dividing the mass (m/z) value at the apex of a peak by the peak width at 5% of the peak height could be indicated as m/?????????????????m10%V
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- -- K. Murray 15:46, 14 Jan 2005 (CST)
