Topic
Mass spectrometry
Page 9 of 15 — Monoisotopic versus average mass, multiply-charged ions and the arithmetic, and why MS/MS is the only real identity test.
Messages — page 9 of 15
fake_trackingif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-01-25typosquat_tayms/ms or it isnt identity#hplc-massspec · 2026-01-25typosquat_tayi have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-01-25acetate_ashgenuine question is monoisotopic or average mass the one on most certificates update from 3 months ago: switched to asking for…#hplc-massspec · 2026-01-25no_appetite_niadoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-01-29stack_scepticif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-01-30factory_direct_fithats a charge state#hplc-massspec · 2026-01-30fridge_thermoif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-01-30HPLC_Hankif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-01-31HPLC_Hanksemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-01-31assay_not_purityms/ms or it isnt identity#hplc-massspec · 2026-01-31ten_of_tendeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-01-31amylin_amyquick one oxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-01-31tail_factorms/ms or it isnt identity#hplc-massspec · 2026-02-01tail_factordeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-02-01tail_factoroxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-02-01void_volumedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-02-02dublin_doseoxidation is about plus 15.99 Da and is usually methionine or tryptophan, i have it written down somewhere#hplc-massspec · 2026-02-02dublin_doseis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-02-02knees_firstoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-02-06deamidationquick one if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic…#hplc-massspec · 2026-02-06patent_2026ms/ms sequencing is the only thing i would call identity. everything else is circumstantial, n of 1 obviously#hplc-massspec · 2026-02-06HPLC_Hankupdate on the earlier thing is monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-02-08assay_not_purityoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-02-08triple_ag_tomms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-02-08assay_not_purityif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-02-08pioneer_piacoming back to this does ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-02-08first_and_last_fouroxidation is about plus 15.99 Da and is usually methionine or tryptophan, i could be wrong#hplc-massspec · 2026-02-09first_and_last_fourthats a charge state#hplc-massspec · 2026-02-09cold_chain_cmdrfollow up deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-02-10LC_MS_Lenaif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-02-10cold_chain_cmdrms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-02-10c18_columnthats a charge state#hplc-massspec · 2026-02-10bac_water_billsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-02-10c18_columnms/ms or it isnt identity#hplc-massspec · 2026-02-10surpass_twoms/ms or it isnt identity#hplc-massspec · 2026-02-12amber_vialms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-02-12amber_vialis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-02-12sharps_comedythats a charge state#hplc-massspec · 2026-02-12area_percentdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-02-12void_volumefollow up does ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-02-15ms_ms_miraif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-02-15brisbane_bacms/ms or it isnt identity#hplc-massspec · 2026-02-15void_volumemonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-02-15boots_supplyright so semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-02-15tallinn_taperif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-02-19wren_weighs_inms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-02-19wren_weighs_inis monoisotopic or average mass the one on most certificates nobody runs enough blanks, including me#hplc-massspec · 2026-02-19retention_timetirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, n of 1 obviously#hplc-massspec · 2026-02-19retention_timedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-02-19salt_bridgei have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-02-23deamidationupdate on the earlier thing is monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-02-23deamidationthats a charge state#hplc-massspec · 2026-02-23rotate_the_siteif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-02-25fasting_insulinis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-02-25salt_bridgei have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-02-25salt_bridgequick one oxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-02-25luerlokms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-02-25quiet.hoursright so semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2, for what its worth#hplc-massspec · 2026-02-25quiet.hoursthats a charge state#hplc-massspec · 2026-02-25