Resolving power (in mass spectrometry)

DRAFT DEFINITION
Resolving power (in mass spectrometry)
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Orange Book Entry

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.

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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[Reference:Marshall 2002] gives the following definitions:

Mass peak width (Δm_50%)

Full width of mass spectral peak at half-maximum peak height

Mass resolving power (Δm/m_50%)

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