Happy new year, everyone!
I have been synthesizing a compound, its mass unit is 440 da and in LCMS(ESI+) I got 441 and (458 major peak).
Could it be possible the 18 da added to the compound mass unit 440 came from H2O or NH4 as ESI+ Common Adducts or something else?
Thank you for your help
Mansour
The ion at m/z 458 was most likely the NH4+ adduct, which is not an uncommon thing in ESI.
If you really want to confirm that, you may analyze the sample (assume your sample was free of ammonium salt) in the following ways:
1. Analyze the sample on a system free of ammonia or ammonium salt, and check if the m/z 458 signal disappears or diminishes
2. Analyze the sample with a mobile phase containing some ammonium salt (assuming your current mobile phase contains no ammonium salt), and check if the m/z 458 signal becomes even more pronounced
If you look hard (review EICs for the relevant ions), you probably will also see Na+ (m/z 463) , K+ (m/z 479) adducts . And this may further support the NH4+ adduct annotation.
I will double check on that!
Thank you for your detailed and helpful answer.
Regards,
Mansour
Hi Mansour,
for a quick overview of ESI adducts I recommend the following links:
https://www.waters.com/webassets/cms/support/docs/bkgrnd_ion_mstr_list.pdf
http://www.rci.rutgers.edu/~layla/AnalMedChem511/LCMS_files/Adducts%20and%20Clusters_LCMS.pdf
https://onlinelibrary.wiley.com/doi/abs/10.1002/1615-9314%2820020801%2925%3A12%3C759%3A%3AAID-JSSC760%3E3.0.CO%3B2-M
https://beta-static.fishersci.ca/content/dam/fishersci/en_US/documents/programs/scientific/brochures-and-catalogs/posters/fisher-chemical-poster.pdf
http://www.proteomicsresource.washington.edu/protocols05/esi_background_ions_repeat_units.php
http://fiehnlab.ucdavis.edu/staff/kind/Metabolomics/MS-Adduct-Calculator
http://www.sc.mahidol.ac.th/scre/cif/PDF/Interferences_and_ContaminantsEncounteredModern.pdf
They are quite useful.
Regards
Markus
You were right, Hanghui Liu, the ion adduct 458 came from NH4+.
Thank you all for your help!
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