Resolution (mass spectrometry)

{{Short description|Measure of resolving power}} {{About|the quantity used in mass spectrometry|other uses|Resolution (disambiguation)}}

In mass spectrometry, '''resolution''' is a measure 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 :<math>R = \cfrac{M}{\Delta M} = \mathrm{resolution}</math> :<math>\Delta M = \mathrm{resolving\ power}</math> :<math>M = \mathrm{mass\ of\ the\ (second)\ peak}</math>

Where a larger resolution indicates a better separation of peaks.<ref name='R05318' >{{GoldBookRef|title=resolution in mass spectroscopy|file=R05318}}</ref><ref>{{GoldBookRef|title=resolving power in mass spectrometry|file=R05321}}</ref> This definition is used in a number of mass spectrometry texts.<ref>{{cite book |title=Mass Spectrometry: Organic Chemical Applications |last=Biemann |first= Klaus |year=1962 |publisher=McGraw-Hill |location=New York |isbn=0-07-005235-2 |page=13 }}</ref><ref name="isbn0-935702-25-3">{{cite book |author1=Tureček, František |author2=McLafferty, Fred W. |title=Interpretation of mass spectra |publisher=University Science Books |location=Sausalito, Calif |year=1993 |isbn=0-935702-25-3 }}</ref><ref name="isbn0-397-51688-6">{{cite book |author=Watson, J. S. |title=Introduction to mass spectrometry |publisher=Lippincott-Raven |location=Philadelphia |year=1997 |isbn=0-397-51688-6 }}</ref><ref name="isbn0-85404-570-8">{{cite book |author=Ashcroft, Alison E. |title=Ionization methods in organic mass spectrometry |publisher=Royal Society of Chemistry |location=Cambridge, Eng |year=1997 |isbn=0-85404-570-8 }}</ref><ref name="isbn3-540-40739-1">{{cite book |author1=JURGEN H. GROSS |author2=Jnrgen H. Gross |title=Mass Spectrometry: A Textbook |publisher=Springer-Verlag |location=Berlin |year=2004 |isbn=3-540-40739-1 }}</ref><ref name="isbn0-471-48888-7">{{cite book |author1=Todd, John F. J. |author2=March, Raymond E. |title=Quadrupole ion trap mass spectrometry |publisher=Wiley-Interscience |location=New York |year=2005 |isbn=0-471-48888-7 }}</ref><ref name="isbn0-9742451-2-7">{{cite book |author=Siuzdak, Gary |author-link=Gary Siuzdak |title=The Expanding Role of Mass Spectrometry in Biotechnology, Second Edition |publisher=MCC Press |year=2006 |isbn=0-9742451-2-7 }}</ref><ref name="isbn0-470-03310-X">{{cite book|author1=Stroobant, Vincent |author2=Hoffmann, Edmond de |title=Mass spectrometry: principles and applications |publisher=J. Wiley |location=London |year=2007 |isbn=978-0-470-03310-4 }}</ref><ref name="isbn0-470-51297-0">{{cite book |author=Ingvar Eidhammer |title=Computational methods for mass spectrometry proteomics |publisher=John Wiley & Sons |location=Chichester |year=2007 |isbn=978-0-470-51297-5 }}</ref> This use is also implied by the term "high-resolution mass spectrometry."<ref name="pmid4896241">{{cite journal |vauthors=VanLear GE, McLafferty FW |title=Biochemical aspects of high-resolution mass spectrometry |journal=Annu. Rev. Biochem. |volume=38 |pages=289–322 |year=1969 |pmid=4896241 |doi=10.1146/annurev.bi.38.070169.001445 }}</ref>

A high value for resolution corresponding to good separation of peaks is similar to the convention used with chromatography separations,<ref name="goldbookR05317">{{GoldBookRef|title=resolution in gas chromatography|file=R05317}}</ref> although the definitions are not the same.<ref name="pmid11758739">{{cite journal |vauthors=Blumberg LM, Kle MS |title=Metrics of separation in chromatography |journal=J Chromatogr A |volume=933 |issue=1–2 |pages=1–11 |date=November 2001 |pmid=11758739 |doi= 10.1016/S0021-9673(01)01256-0}}</ref> High resolution indicating better peak separation is also used in ion mobility spectrometry.<ref name="isbn0-8493-2247-2">{{cite book |author1=Karpas, Zeev |author2=Eiceman, Gary Alan |title=Ion mobility spectrometry |publisher=CRC Press |location=Boca Raton |year=2005 |isbn=0-8493-2247-2 }}</ref>

===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: :<math>R = \cfrac{M}{\Delta M} = \mathrm{resolving\ power}</math>

The minimum peak separation ΔM which allows to distinguish two ion species is then called: :<math>\Delta M = \mathrm{resolution} </math>

Resolution and resolving power, when defined in this way, are consistent with IUPAC recommendations for microscopy, optical spectroscopy.<ref>{{GoldBookRef|title=resolution in optical spectroscopy|file=R05319}}</ref><ref>{{GoldBookRef|title=resolving power in optical spectroscopy|file=R05322}}</ref> and ion microscopy (SIMS) <ref>{{GoldBookRef|title=resolving power in ion microscopy|file=I03221}}</ref> but not gas chromatography.<ref name="goldbookR05317"/> This definition also appears in some mass spectrometry texts.<ref name="isbn0-9660813-9-0">{{cite book |author=David O. Sparkman |title=Mass Spectrometry Desk Reference |publisher=Global View Pub |location=Pittsburgh |year=2006 |isbn=0-9660813-9-0 }}</ref><ref name="isbn0-470-51634-8">{{cite book |author=Sparkman, O. David |title=Introduction to mass spectrometry: instrumentation, applications and strategies for data interpretation |publisher=John Wiley & Sons |location=Chichester |year=2007 |isbn=978-0-470-51634-8 }}</ref><ref name="isbn0-471-68229-2">{{cite book |author=Dass, Chhabil |title=Fundamentals of contemporary mass spectrometry |publisher=John Wiley & Sons |location=Chichester |year=2007 |isbn=978-0-471-68229-5 }}</ref>

==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.<ref name='R05318' />

===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.<ref name='R05318' />

==References== {{Reflist}}

Category:Mass spectrometry