Hello,
I was wondering what the acceptable +/- ppm window is when identifying a compound? I am obtaining accurate mass data with an LC-ESI-TOF-MS and I know XCMS searches metlin within 0.15. Just wanted to get the general opinion before I start searching other databases-
Thank you!
Ashley
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Metabolite identification
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Metabolite identification
by AmSidebottomIU » Mon Aug 08, 2011 12:52 pm
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Re: Metabolite identification
by Ralf » Mon Aug 08, 2011 1:33 pm
The ppm window depends on your instrument accuray. For a TOF, 10-30 ppm would be normal.
However, the result of a database search by exact mass should only be considered a putative ID.
Even with 0 ppm mass deviation, the correct ID has to be verified by MS/MS and retention time of a standard.
e.g., a METLIN search for m/z 181.0707, [M+H]+ only, will result in 19 hits with 0 ppm.
However, the result of a database search by exact mass should only be considered a putative ID.
Even with 0 ppm mass deviation, the correct ID has to be verified by MS/MS and retention time of a standard.
e.g., a METLIN search for m/z 181.0707, [M+H]+ only, will result in 19 hits with 0 ppm.
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