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| {{Infobox unit
| | Hello and welcome. My title is Ling. Some time ago he chose to reside in Idaho. Camping is something that I've carried out for years. My job is a messenger.<br><br>My weblog: [http://Checkmates.co.za/index.php?do=/profile-1592/info/ aftermarket car warranty] |
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| | name = thomson
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| | standard =
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| | quantity = [[Mass-to-charge ratio]]
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| | symbol = Th
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| | namedafter = [[J. J. Thomson]]
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| The '''thomson''' (symbol: '''Th''') is a unit that has appeared infrequently in scientific literature relating to the field of [[mass spectrometry]] as a unit of [[mass-to-charge ratio]]. The unit was proposed by Cooks and Rockwood<ref> {{cite journal|title=The 'Thomson'. A suggested unit for mass spectroscopists|journal=[[Rapid Communications in Mass Spectrometry]]|date=1991|first=R. G.|last=Cooks|coauthors=A. L. Rockwood|volume=5|issue=2|page=93|id= |url=|format= }}</ref> naming it in honour of [[J. J. Thomson]] who measured the [[mass-to-charge ratio]] of electrons and ions.
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| ==Definition==
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| The thomson is defined as<ref name='Stroobant'>{{cite book |author=Stroobant, Vincent; Hoffmann, Edmond de; Charette, Jean Joseph |title=Mass spectrometry: principles and applications |publisher=Wiley |location=New York |year=1996 |pages= |isbn=0-471-96696-7 |oclc= |doi=}}</ref>
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| :<math> 1~\mathrm{Th} = 1~\frac{\mathrm{u}}{e} = 1~\frac{\mathrm{Da}}{e} = 1.036426 \times 10^{-8}\,kg\,C^{-1}</math>
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| where '''u''' represents the [[unified atomic mass unit]], Da represents the unit dalton, and ''e'' represents the [[elementary charge]] which is the [[electric charge]] [[Units of measurement|unit]] in the [[atomic unit]] system.
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| For example, for the ion C<sub>7</sub>H<sub>7</sub><sup>2+</sup> has an exact mass of 91.0 Da. Its charge number is +2, and hence its charge is 2''e''. The ion will be observed at 45.5 Th in a mass spectrum.
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| The thomson allows for negative values for negatively charged ions. For example, the [[benzoate]] anion would be observed at ''m/z'' 121, but at −121 Th since the charge is −e.
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| ==Use==
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| The thomson has been used by some mass spectrometrists, for example [[Alexander Alexeyevich Makarov|Alexander Makarov]]—the inventor of the [[Orbitrap]]—in a scientific poster,<ref>[http://www.asms.org/asms99pdf/095.pdf The Orbitrap: a novel high-performance electrostatic trap (ASMS)]</ref> papers,<ref>{{cite journal |author=Pakenham G, Lango J, Buonarati M, Morin D, Buckpitt A |title=Urinary naphthalene mercapturates as biomarkers of exposure and stereoselectivity of naphthalene epoxidation |journal=Drug Metab. Dispos. |volume=30 |issue=3 |pages=247–53 |year=2002 |pmid=11854141 |doi= 10.1124/dmd.30.3.247|url=http://dmd.aspetjournals.org/cgi/pmidlookup?view=long&pmid=11854141}}</ref><ref>{{cite journal |author=Mengel-Jørgensen J, Kirpekar F |title=Detection of pseudouridine and other modifications in tRNA by cyanoethylation and MALDI mass spectrometry |journal=Nucleic Acids Res. |volume=30 |issue=23 |pages=e135 |year=2002 |pmid=12466567 |doi= 10.1093/nar/gnf135|url=http://nar.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=12466567 |pmc=137990}}</ref>
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| and (notably) one book.<ref name='Stroobant' /> The journal [[Rapid Communications in Mass Spectrometry]] (in which the original article appeared) states that "the Thomson (Th) may be used for such purposes as a unit of mass-to-charge ratio although it is not currently approved by IUPAP or IUPAC."<ref>{{cite web|url=http://www3.interscience.wiley.com/journal/4849/home/ForAuthors.html |title=Rapid Communications in Mass Spectrometry Instructions to Authors |accessdate=2007-12-03 |publisher=Wiley Interscience }}</ref> Even so, the term has been called "controversial" by RCM's former Editor-in Chief<ref>{{cite journal|title=Book Review: Mass Spectrometry: Principles and Applications. E. de Hoffman, J. Charette and W. Stroobant. Wiley, Chichester 1996. ISBN 0-471-96697-5|journal=Rapid Communications in Mass Spectrometry|date=4 December 1998|first=Robert K.|last=Boyd|coauthors=|volume=11|issue=8|page=948|doi= 10.1002/(SICI)1097-0231(199705)11:8<948::AID-RCM2033>3.0.CO;2-I|url=|format= }}</ref> (in a review the Hoffman text cited above<ref name="Stroobant"/>). The book, ''Mass Spectrometry Desk Reference'', argues against the use of the thomson.<ref name="isbn0-9660813-2-3">{{cite book |author=Sparkman, O. David |title=Mass spectrometry desk reference |publisher=Global View Pub |location=Pittsburgh |year=2000 |pages= |isbn=0-9660813-2-3 |oclc= |doi=}}</ref> However, the editor-in-chief of the [[Journal of the Mass Spectrometry Society of Japan]] has written an editorial in support of the thomson unit.<ref>{{cite journal|title=Comments on Abscissa Labeling of Mass Spectra|journal=Journal of the Mass Spectrometry Society of Japan|year=2007|first=|last=|coauthors=|volume=55|issue=1|pages=51–61|id= |url=http://db.wdc-jp.com/mssj/search/abst/200701/ms550051.html|accessdate=2007-12-05|doi=10.5702/massspec.55.51|last1=Yoshino|first1=Ken-Ichi }}</ref>
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| The thomson is not an [[SI unit]], nor has it been defined by [[IUPAC]].
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| == References ==
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| {{Reflist}}
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| [[Category:Units of measurement]]
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| [[Category:Mass spectrometry]]
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Hello and welcome. My title is Ling. Some time ago he chose to reside in Idaho. Camping is something that I've carried out for years. My job is a messenger.
My weblog: aftermarket car warranty