# Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Resolution (mass spectrometry)

In mass spectrometry, resolution measures of the ability to distinguish two peaks of slightly different mass-to-charge ratios ΔM, in a mass spectrum.

## Resolution and Resolving Power

There are two different definitions of resolution and resolving power in mass spectrometry.

### IUPAC definition

The IUPAC definition for resolution in mass spectrometry is
    $R={\cfrac {M}{\Delta M}}$ = resolution
    $\Delta M$ = resolving power
where a larger resolution indicates a better separation of peaks. This definition is used in a number of mass spectrometry texts. This use is also implied by the term "high-resolution mass spectrometry."
A high value for resolution corresponding to good separation of peaks is similar to the convention used with chromatography separations, although it is important to note that the definitions are not the same. High resolution indicating better peak separation is also used in ion mobility spectrometry
IUPAC defines Δm as the resolving power.

### Resolving power definition

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:
    $R={\cfrac {M}{\Delta M}}$ = resolving power.
The minimum peak separation ΔM which allows to distinguish two ion species is then called:
    $\Delta M$ = resolution.
Resolution and resolving power, when defined in this way, are consistent with IUPAC recommendations for microscopy, optical spectroscopy. and ion microscopy (SIMS) but not gas chromatography. This definition also appears in some mass spectrometry texts.

## Measuring peak separation

There are several ways to define the minimum peak separation ΔM in mass spectrometry, therefore it is important to report the method used to determine mass resolution when reporting its value. The two most widely used are the peak width definition and the valley definition.

### Peak width definition

In the peak width definition, the value of Δm is the width of the peak measured at a specified fraction of the peak height, for example 0.5%, 5%, 10% or 50%. The latter is called the full width at half maximum (FWHM).

### Valley definition

The valley definition defines ΔM as the closest spacing of two peaks of equal intensity with the valley (lowest value of signal) between them less than a specified fraction of the peak height. Typical values are 10% or 50%. The value obtained from a 5% peak width is roughly equivalent to a 10% valley.

## References

* 1 2 3 International Union of Pure and Applied Chemistry. "resolution in mass spectroscopy". Compendium of Chemical Terminology Internet edition.
* ↑ Biemann, Klaus (1962). Mass Spectrometry: Organic Chemical Applications. New York: McGraw-Hill. p. 13. ISBN 0070052352. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
* ↑ Tureček, František; McLafferty, Fred W. (1993). Interpretation of mass spectra. Sausalito, Calif: University Science Books. ISBN 0-935702-25-3.{{cite book}}: CS1 maint: multiple names: authors list (link)
* ↑ Watson, J. S. (1997). Introduction to mass spectrometry. Philadelphia: Lippincott-Raven. ISBN 0-397-51688-6.
* ↑ Ashcroft, Alison E. (1997). Ionization methods in organic mass spectrometry. Cambridge, Eng: Royal Society of Chemistry. ISBN 0-85404-570-8.
* ↑ JURGEN H. GROSS; Jnrgen H. Gross (2004). Mass Spectrometry: A Textbook. Berlin: Springer-Verlag. ISBN 3-540-40739-1.{{cite book}}: CS1 maint: multiple names: authors list (link)
* ↑ Todd, John F. J.; March, Raymond E. (2005). Quadrupole ion trap mass spectrometry. New York: Wiley-Interscience. ISBN 0-471-48888-7.{{cite book}}: CS1 maint: multiple names: authors list (link)
* ↑ Siuzdak, Gary (2006). The Expanding Role of Mass Spectrometry in Biotechnology, Second Edition. MCC Press. ISBN 0-9742451-2-7.
* ↑ Stroobant, Vincent; Hoffmann, Edmond de (2007). Mass spectrometry: principles and applications. London: J. Wiley. ISBN 0-470-03310-X.{{cite book}}: CS1 maint: multiple names: authors list (link)
* ↑ Ingvar Eidhammer (2007). Computational methods for mass spectrometry proteomics. Chichester: John Wiley & Sons. ISBN 0-470-51297-0.
* ↑ VanLear GE, McLafferty FW (1969). "Biochemical aspects of high-resolution mass spectrometry". Annu. Rev. Biochem. 38: 289–322. doi:10.1146/annurev.bi.38.070169.001445. PMID 4896241.
* ↑ International Union of Pure and Applied Chemistry. "resolution in gas chromatography]]". Compendium of Chemical Terminology Internet edition.
* ↑ Blumberg LM, Kle MS (2001). "Metrics of separation in chromatography". J Chromatogr A. 933 (1–2): 1–11. doi:10.1016/S0021-9673(01)01256-0. PMID 11758739. {{cite journal}}: Unknown parameter |month= ignored (help)
* ↑ Karpas, Zeev; Eiceman, Gary Alan (2005). Ion mobility spectrometry. Boca Raton: CRC Press. ISBN 0-8493-2247-2.{{cite book}}: CS1 maint: multiple names: authors list (link)
* ↑ International Union of Pure and Applied Chemistry. "resolving power in mass spectrometry". Compendium of Chemical Terminology Internet edition.
* ↑ International Union of Pure and Applied Chemistry. "resolution in optical spectroscopy". Compendium of Chemical Terminology Internet edition.
* ↑ International Union of Pure and Applied Chemistry. "resolving power in optical spectroscopy". Compendium of Chemical Terminology Internet edition.
* ↑ International Union of Pure and Applied Chemistry. "resolving power in ion microscopy". Compendium of Chemical Terminology Internet edition.
* ↑ International Union of Pure and Applied Chemistry. "resolution in gas chromatography". Compendium of Chemical Terminology Internet edition.
* ↑ David O. Sparkman (2006). Mass Spectrometry Desk Reference. Pittsburgh: Global View Pub. ISBN 0-9660813-9-0.
* ↑ Sparkman, O. David (2007). Introduction to mass spectrometry: instrumentation, applications and strategies for data interpretation. Chichester: John Wiley & Sons. ISBN 0-470-51634-8.
* ↑ Dass, Chhabil (2007). Fundamentals of contemporary mass spectrometry. Chichester: John Wiley & Sons. ISBN 0-471-68229-2.