Topic
Mass spectrometry
Page 13 of 15 — Monoisotopic versus average mass, multiply-charged ions and the arithmetic, and why MS/MS is the only real identity test.
Messages — page 13 of 15
ferrous_ashif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic, ill dig out…#hplc-massspec · 2026-05-06endotoxin_edif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-05-06endotoxin_edupdate on the earlier thing ms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-06kelp_keepsoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-05-06kelp_keepstirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-06nordic_price_nilsdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant two labs a point or two apart on the same lot…#hplc-massspec · 2026-05-07hydrate_hanatirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-07factory_direct_fiif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-05-07nordic_price_nilsdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-05-07LC_MS_Lenathats a charge state#hplc-massspec · 2026-05-07LC_MS_Lenaoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-05-07flint_fillssemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-05-07LC_MS_Lenatirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-08LC_MS_Lenasemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-05-08peak_splitmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-05-08bac_water_billthats a charge state#hplc-massspec · 2026-05-09pinch_not_stretchdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-05-09madrid_mgif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result, thats one data point#hplc-massspec · 2026-05-09pinch_not_stretchoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-05-09pinch_not_stretchms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-09rowan_readsdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-05-10juno_joinsis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-05-10brisbane_bacms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-10forty_five_kgok so tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-10forty_five_kgoxidation is about plus 15.99 Da and is usually methionine or tryptophan, i have it written down somewhere#hplc-massspec · 2026-05-10aliquot_adaif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-05-10aliquot_adai have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-05-10auckland_aliquotsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-05-10HPLC_Hanki have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-05-11HPLC_Hankms/ms or it isnt identity#hplc-massspec · 2026-05-12two_four_ceilingsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-05-12dark_for_ten_daysms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-12dark_for_ten_daysslightly off topic but i have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-05-12gip_glp_gilunrelated but if the number you are staring at is a third of what you expected, do the charge state arithmetic before you…#hplc-massspec · 2026-05-12gip_glp_gildeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-05-12gip_glp_gilif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result, from memory#hplc-massspec · 2026-05-12gip_glp_giloxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-05-12slow.taperwhile im here tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-13slow.tapermonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-05-13slow.taperok so i have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-05-13jute_journalsfollow up semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-05-13deamidationis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-05-13still_here_2024deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-05-13deamidationif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-05-13spreadsheet_stutirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-05-14deamidationquick one deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-05-14deamidationis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-05-14vat_on_importms/ms or it isnt identity#hplc-massspec · 2026-05-14vat_on_importthats a charge state#hplc-massspec · 2026-05-14marrow.modms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-14a1c_lagms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-05-15a1c_lagms/ms or it isnt identity#hplc-massspec · 2026-05-15void_volumeis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-05-15a1c_lagif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-05-15elder_eusorry to jump in deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-05-15see_a_clinicianslightly off topic but if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result…#hplc-massspec · 2026-05-15verify_or_dontdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-05-16area_percentmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-05-16verify_or_donti have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-05-16lyophile_livoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-05-17