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| =Note: The ''m/q'' notation is a non-standard usage in mass spectrometry that has never been widely accepted. The arguments below are included for the purposes of discussion only.=
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| {{Sugdef|m/q|
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| m/Q is the symbol for a physical quantity [[Mass/charge Ratio|mass/charge]] which is measured by [[Mass Spectrometer|mass spectrometers]].
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| The former ''[[m/z]]'' is based on a [[Talk:Mass/Charge Ratio (Th, never use Da, no units?. An ion of m/z or an ion at m/z?)|missconception]] and should no longer be used.
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| The SI unit of the physical quantity ''m/Q'' is kilogram/coulomb ('''kg/C''').
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| In [[Mass Spectrometry | mass spectrometry]] it is more common to use the [[Atomic Mass Unit]] '''u''' and the [http://www.iupac.org/goldbook/A00504.pdf atomic unit] for charge '''e''' which is equal to the [http://www.iupac.org/goldbook/E02032.pdf elementary charge].
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| This means the unit for mass/charge is:
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| : [''m/Q''] = '''u'''/'''e'''
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| For simplicity, '''u''' is better called [[Dalton]] ('''Da''') and '''e''' is called [[Millikan]] ('''Mi''').
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| '''u'''/'''e''' is sometimes called [[Thomson]] ('''Th''').
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| Therefore
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| : [''m/Q''] = '''u'''/'''e''' = '''Da'''/'''Mi''' = '''Th'''
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| Hence, a [[Mass Spectrum | mass spectrum]] x-axis should be labeled as either of the below:
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| * ''m/Q'' ('''u'''/'''e''')
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| * ''m/Q'' ('''Da'''/'''Mi''')
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| * ''m/Q'' ('''Th''')
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| '''References'''
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| :[http://www.iupac.org/goldbook/Q04982.pdf gold book: quantity]
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| :[http://www.iupac.org/goldbook/P04666.pdf gold book: physical quantity]
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| :[http://www.iupac.org/goldbook/V06593.pdf gold book: value of a quantity]
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| }}
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