Resolution (mass spectrometry)
Obsolete Template
Controversy
IUPAC and ASMS 1991 (Price 1991) define resolution as m/Δm.
ASMS 1997 (Voyksner 1997), Marshall (Marshall 2002), Sparkman (Sparkman 2006) define resolution as Δm and resolving power as m/Δm.
Gold Book
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). |
| Resolution (mass spectrometry) |
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resolution in mass spectroscopy [sic] (energy): By analogy with the peak width definition for mass resolution, a peak showing the number of ions as a function of their translational energy should be used to give a value for the energy resolution. (10 per cent valley definition): Let two peaks of equal height in a mass spectrum at masses m and m - Δm be separated by a valley which at its lowest point is just 10 per cent of the height of either peak. For similar peaks at a mass exceeding m, let the height of the valley at its lowest point be more (by any amount) than ten per cent of either peak height. Then the resolution (10 per cent valley definition) is m/Δm. It is usually a function of m. The ratio m/Δm should be given for a number of values of . (peak width definition): For a single peak made up of singly charged ions at mass in a mass spectrum, the resolution may be expressed as where is the width of the peak at a height which is a specified fraction of the maximum peak height. It is recommended that one of three values 50%, 5% or 0.5% should always be used. For an isolated symmetrical peak recorded with a system which is linear in the range between 5% and 10% levels of the peak, the 5% peak width definition is technically equivalent to the 10% valley definition. A common standard is the definition of resolution based upon being Full Width of the peak at Half its Maximum height, sometimes abbreviated 'FWHM'. This acronym should preferably be defined the first time it is used. Source: PAC, 1991, 63, 1541 (Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)) on page 1554 Orange Book, p. 203 |
| IUPAC Gold Book |
| Index of Gold Book Terms |
Orange Book
Resolution: 10 Per Cent Valley Definition
Let two peaks of equal height in a mass spectrum at masses m and m - Δm be separated by a valley which at its lowest point is just 10% of the height of either peak. For similar peaks at a mass exceeding m , let the height of the valley at its lowest point be more (by any amount) than 10% of either peak. Then the resolution (10% valley definition) is m / Δm. The ratio m /Δm should be given for a number of values of m.
Resolution: Peak Width Definition
For a single peak made up of singly charged ions at mass m in a mass spectrum, the resolution may be expressed as m / Δm, where Δm is the width of the peak at a height which is a specified fraction of the maximum peak height. It is recommended that one of three values 50%, 5% or 0.5% should always be used. (Note that for an isolated symmetrical peak recorded with a system which is linear in the range between 5% and 10% levels of the peak, the 5% peak width definition is equivalent to the 10% valley definition. A common standard is the definition of resolution based upon Δm being Full Width of the peak at Half its Maximum (FWHM) height.
Price 1991
Resolution: 10% valley definition, m/Δm. Let two peaks of equal height in a mass spectrum at masses m and m-Δm be???????????separated by a valley that at its lowest point is just 10% of the height of either peak. For similar peaks at a mass exceeding m, let the height of the valley at its lowest point be more (by any amount) than 10% of either peak height. Then the resolution (10% valley definition) is m/Δm. It is usually a func- tion of m, therefore m/Δm should be given for a number of values of m.
Resolution: peak width definition, m/Δm. For a single peak made up of singly charged ions at mass m in a mass spectrum, the resolution may be expressed as m/Δm, where Am is the width of the peak at a height that is a specified fraction of the maximum peak height. It is recommended that one of three values 50%, 5%, or 0.5% be used. For an isolated symmetrical peak, recorded with a system that is linear in the range between 5% and 10% levels of the peak, the 5% width defmition is technically equivalent to the Photo-ionization. 10% valley defmition. A common standard is the definition of resolution based upon Δm being full width of the Desk at half its maximum heieht, sometimes abbreviated ??????????FWHM.??????????
Resolving power (mass). The ability to distinguish between ions differing slightly in mass-to-charge ratio. 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, specihcally for 50% and for 5% of the maximum peak height.
1997 ASMS Poster
From the ASMS Terms and Definitions Poster:
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, Dmx 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/Dmx, where Dmx 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/Dm10%V theoretical mass resolving power -
Usage note: Theoretical mass resolving power is useful for determining the relative difficulty in separating two peaks in a mass spectrum. The "masses" are actually m/z values, and the subscript "d" indicates that the criterion used to determine Dm is simply the difference in mass between the two peaks. One should be careful to notice the subtle distinction between Dmd, a quantity that is independent of instrumental performance, and Dmx, a quantity that is determined by instrumental performance. It is important to realize that the theoretical mass resolving power makes no peak shape assumptions. Therefore, the choice of overlap criterion, i.e., 10% valley, full width half height, etc. is the link between the theoretical mass resolving power and the experimentally measured "mass resolving power." For an instrument to be capable of separating two particular ions, the instrument must possess a mass resolving power (over the range m + Dm) that is greater than the theoretical mass resolving power calculated for the ions in question. For example, if it is desired to determine whether or not a particular mass spectrometer is capable of resolving 41K+ from 40Ar1H+, determine the theoretical mass resolving power:
Next, the instrumental mass resolving power of the instrument at m/z = 41 is compared with the theoretical mass resolving power. For a quadrupole based instrument, a 10% valley overlap would correspond to a Dm of approximately 1 Da, assuming typical scan rates are used. For a peak at m/z = 41, this corresponds to a "mass resolving power" = 41. Therefore, this particular instrument does not possess mass resolving power capable of separating these two species. >From the preceding discussion, it is apparent that even greater mass resolving power would be required for a separation if two adjacent peaks if the peaks are not of equal size and shape. The lesser peak could be lost in the "wings" of the larger peak.
Another comment: Note that resolving power is dimensionless, but when defined as peakwidth, it usually has units of "parts-per-million" (of mass). Thus, a resolution of 10,000 corresponds to 100 ppm.
Definition of resolution in mass spectrometry books
Books defining resolution as m/Δm
- Mass Spectrometry and its Applications to Organic Chemistry
- J. H. Beynon
- Elsevier, 1960
- Mass Spectrometry ???????????? Organic Chemical Applications
- Klaus Biemann
- McGraw-Hill, 1962
- Lasers and Mass Spectrometry
- By David M. Lubman
- Oxford University Press US, 1990
- ISBN 0195059298
- Interpretation of Mass Spectra
- Fred W. McLafferty, Turecek
- University Science Books, 1993
- Language: English
- ISBN 0935702253
- Mass Spectrometry: Clinical and Biomedical Applications
- By Dominic M. Desiderio
- Springer, 1993
- ISBN 0306442612
- Practical Organic Mass Spectrometry: A Guide for Chemical and Biochemical Analysis
- J. R. Chapman
- Wiley_Default, 1995
- ISBN 047195831X
- Mass Spectrometry for Chemists and Biochemists
- Robert Alexander Walker Johnstone, M. E. Rose
- Cambridge University Press, 1996
- ISBN 0521424976
- Introduction to Mass Spectrometry
- By J. Throck Watson
- Lippincott-Raven, 1997
- ISBN 0397516886
- Ionization Methods in Organic Mass Spectrometry
- By Alison E. Ashcroft, Royal Society of Chemistry (Great Britain)
- Royal Society of Chemistry, 1997
- ISBN 0854045708
- Accelerator Mass Spectrometry: Ultrasensitive Analysis for Global Science
- Claudio Tuniz, John R. Bird, Gregory F. Herzog, David Fink
- CRC Press, 1998
- ISBN 0849345383
- Mass Spectrometry in Biology & Medicine
- By A. L. Burlingame, Steven A. Carr, Michael A. Baldwin
- Humana Press, 1999
- ISBN 0896037991
- Mass Spectrometry and Genomic Analysis
- J. Nicholas Housby
- Springer, 2001
- ISBN 0792371739
- Mass Spectrometry Basics
- Christopher G. Herbert, Robert Alexander Walker Johnstone
- CRC Press, 2002
- ISBN 0849313546
- Liquid Chromatography Mass Spectrometry: An Introduction Robert E. Ardrey
- Wiley, 2003
- ISBN 0471498017
- Mass Spectrometry: A Textbook
- J???????rgen H. Gross
- Springer, 2004
- ISBN 3540407391
- Quadrupole Ion Trap Mass Spectrometry
- By Raymond E. March, John F. Todd
- Wiley-IEEE, 2005
- ISBN 0471717975
- The Expanding Role of Mass Spectrometry in Biotechnology
- Gary Siuzdak
- McC Pr, 2006
- ISBN 0974245127
- Quantitative Applications of Mass Spectrometry
- Pietro Traldi, Franco Magno, Irma Lavagnini, Roberta Seraglia
- Wiley, 2006
- ISBN 0470025166
- Assigning Structures to Ions in Mass Spectrometry
- John L. Holmes, Christiane Aubry, Paul M. Mayer
- CRC, 2006
- ISBN 0849319501
- Mass Spectrometry: Principles and Applications
- Edmond de Hoffmann, Vincent Stroobant
- Wiley-Interscience, 2007
- ISBN 047003310X
- Quantitative Proteomics by Mass Spectrometry (Methods in Molecular Biology)
- Salvatore Sechi
- Humana Press, 2007
- ISBN 1588295710
- Computational Methods for Mass Spectrometry Proteomics
- Ingvar Eidhammer, Kristian Flikka, Lennart Martens, Svein-Ole Mikalsen
- Wiley-Interscience, 2008
- ISBN 0470512970
Books defining resolution as Δm
- Mass Spectrometry Desk Reference
- David Sparkman
- Global View, 2006
- ISBN 0966081390
- Introduction to Mass Spectrometry: Instrumentation, Applications, and Strategies for Data Interpretation
- J. Throck Watson, O. David Sparkman
- Wiley, 2007
- Language: English
- ISBN 0470516348
- Fundamentals of Contemporary Mass
- Chhabil Dass, 2007
- ISBN 0471682292
- Proteomics in Practice: A Guide to Successful Experimental Design
- Reiner Westermeier, Tom Naven, Hans-Rudolf H??????pker
- Wiley, 2008
- ISBN 3527319417
