Topic
Mass spectrometry
Page 7 of 15 — Monoisotopic versus average mass, multiply-charged ions and the arithmetic, and why MS/MS is the only real identity test.
Messages — page 7 of 15
blank_runms/ms or it isnt identity#hplc-massspec · 2025-11-12salt_bridgeright so if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-11-12blank_runthats a charge state#hplc-massspec · 2025-11-12endotoxin_edoxidation is about plus 15.99 Da and is usually methionine or tryptophan, for what its worth#hplc-massspec · 2025-11-12coa_or_copems/ms sequencing is the only thing i would call identity. everything else is circumstantial, not advice obviously#hplc-massspec · 2025-11-12salt_bridgeis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-11-12salt_bridgesemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2025-11-12area_percentoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-11-13travel_coolersemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2025-11-13vik_verifiesmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-11-15area_percenttirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2025-11-15area_percentoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-11-15vik_verifiesis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-11-15area_percentsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2, happy to be corrected#hplc-massspec · 2025-11-15batch_banditdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-11-15declared_valueif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic, ymmv#hplc-massspec · 2025-11-16verify_or_dontms/ms sequencing is the only thing i would call identity. everything else is circumstantial, n of 1 obviously#hplc-massspec · 2025-11-16eat_more_pleasedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-11-16vialkeeperif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-11-16provincial_patthats a charge state#hplc-massspec · 2025-11-16relabel_watchms/ms or it isnt identity#hplc-massspec · 2025-11-19salt_bridgethats a charge state#hplc-massspec · 2025-11-19area_percentdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-11-19thirty_min_waitdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant, happy to be corrected#hplc-massspec · 2025-11-19point_two_fiveif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-11-19gradient_gregif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-11-21lisbon_lotif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-11-21area_percentif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-11-24charge_statems/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-11-24monoisotopicdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-11-24deamidationtirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, thats just me#hplc-massspec · 2025-11-29void_volumems/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-11-29HPLC_Hankms/ms or it isnt identity#hplc-massspec · 2025-11-29HPLC_Hankmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-11-29tarpit_tamtirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2025-11-30melb_meniscusquick one does ms/ms actually prove identity or just make it very likely deamidation is about plus 0.98 Da. it is not a…#hplc-massspec · 2025-11-30coa_or_copedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant, ask me again in a month#hplc-massspec · 2025-12-01still_here_2024is monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-12-01no_chargebackif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-12-01turnaround_tamgenuine question monoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-12-01cold_chain_cmdryour day job probably does not involve posting mass spectra at midnight#vendor-verification · 2025-12-02pinch_not_stretchgenuine question is monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-12-03monoisotopici have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-12-03monoisotopicif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-12-03bengaluru_bacmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-12-04area_percentif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-12-04stable_not_volatilefor the archive ms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-12-04bengaluru_bacdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-12-04electrolyte_eliis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-12-04pbs_pipif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-12-08pbs_piptirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2025-12-08two_eight_cms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-12-08mg_per_mloxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-12-11mg_per_mli have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-12-11surpass_twothats a charge state#hplc-massspec · 2025-12-11unsolicited_dmthats a charge state#hplc-massspec · 2025-12-12power_through_noms/ms or it isnt identity#hplc-massspec · 2025-12-12monoisotopicif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-12-13monoisotopicmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-12-13snac_and_waterupdate on the earlier thing deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-12-13