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)
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Orange Book
| ORANGE BOOK DEFINITION
IUPAC. Analytical Division. Compendium of Analytical Nomenclature (the Orange Book). Definitive Rules, 1979 (see also Orange Book 2023) |
| Resolving power (in mass spectrometry) |
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The ability to distinguish between ions differing in the quotient mass/charge by a small increment. It may be characterized by giving the peak width, measured in mass units, expressed as a function of mass, for at least two points on the peak, specifically for 50% and for 5% of the maximum peak height. |
| IUPAC 1997 Orange Book Chapter 12 |
| Index of Orange Book Terms |
Gold Book
| GOLD BOOK DEFINITION
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the Gold Book). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). |
| Resolving power (in mass spectrometry) |
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Resolving power (mass spectrometry) http://goldbook.iupac.org/R05321.html The ability to distinguish between ions differing in the quotient mass/charge by a small increment. It may be characterized by giving the peak width, measured in mass units, expressed as a function of mass, for at least two points on the peak, specifically at fifty percent and at five percent of the maximum peak height. mass resolving power http://goldbook.iupac.org/M03730.html Commonly and also acceptably defined in terms of the overlap (or 'valley') between two peaks. Thus for two peaks of equal height, masses and , when there is overlap between the two peaks to a stated percentage of either peak height (10% is recommended), then the resolving power is defined as . The percentage overlap (or 'valley') concerned must always be stated. Source: PAC, 1978, 50, 65 (Recommendations for symbolism and nomenclature for mass spectroscopy) on page 72 |
| IUPAC Gold Book |
| Index of Gold Book Terms |
See also
External links
- Reference:Marshall 2002 gives the following definitions:
- Mass peak width (Δm50%)
- Full width of mass spectral peak at half-maximum peak height
- Mass resolving power (m/Δm50%)
- A well-isolated single mass spectral peak
- Mass resolution (m2 m1 in Da, or (m2 m1)/m1 in ppm)
- The smallest mass difference between equal magnitude peaks such that the valley between them is a specified fraction of either peak height
- Mass precision
- Root-mean-square deviation in a large number of repeated measurements
- Mass accuracy
- Difference between measured and actual mass
- Mass defect
- Difference between exact and nominal mass
