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

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