Topic
Mass spectrometry
Page 15 of 15 — Monoisotopic versus average mass, multiply-charged ions and the arithmetic, and why MS/MS is the only real identity test.
Messages — page 15 of 15
food_noise_offms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-06-08per_mg_peteoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-06-12ferritin_fayif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-06-12void_volumetirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-06-12ms_ms_mirams/ms or it isnt identity#hplc-massspec · 2026-06-13site_itchoxidation is about plus 15.99 Da and is usually methionine or tryptophan, ill dig out the number#hplc-massspec · 2026-06-13panel_before_afterthats a charge state#hplc-massspec · 2026-06-13peak_splitmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-06-14retention_timefor the archive tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-06-14peak_splitis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-06-14bp_down_bexoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-06-14deamidationms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-06-14area_percentms/ms or it isnt identity#hplc-massspec · 2026-06-14mira_pinsoxidation is about plus 15.99 Da and is usually methionine or tryptophan you need more sample for identity than for purity.…#hplc-massspec · 2026-06-16LC_MS_Lenams/ms sequencing is the only thing i would call identity. everything else is circumstantial co-elution is the failure mode…#hplc-massspec · 2026-06-16LC_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 · 2026-06-17orfor_watchi have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-06-17yyz_vialdoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-06-17olive_ordersms/ms or it isnt identity#hplc-massspec · 2026-06-17factory_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 · 2026-06-17orfor_watchdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-06-17nordic_price_nilsis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-06-17monoisotopicslightly off topic but ms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-06-18group_buy_gwenmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting, still working it out#hplc-massspec · 2026-06-18karl_fischerif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-06-18karl_fischerright so oxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-06-18chlorhexi have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2026-06-18coa_or_cope[redacted at member request]#hplc-massspec · 2026-06-18coa_or_copetirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-06-18drawup_deems/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2026-06-19drawup_deedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-06-19drawup_deeis monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-06-19related_substhats a charge state#hplc-massspec · 2026-06-20snac_and_waterif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result, thats just me#hplc-massspec · 2026-06-20a1c_lagif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-06-20auckland_aliquotsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-06-20cat_on_the_traysemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-06-23cat_on_the_trayif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result, ask me again in a month#hplc-massspec · 2026-06-23plateau_penif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-06-23area_percentthats a charge state#hplc-massspec · 2026-06-26area_percentif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2026-06-26blank_rundoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2026-06-26dose_down_darams/ms or it isnt identity#hplc-massspec · 2026-06-26dose_down_daratirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2026-06-26pinch_not_stretchmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-06-26acetate_ashgenuine question deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant, happy to be corrected#hplc-massspec · 2026-06-26half_life_halsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-06-26assay_not_purityms/ms sequencing is the only thing i would call identity. everything else is circumstantial, thats one data point#hplc-massspec · 2026-06-26void_volumedeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2026-06-27no_chargebackms/ms or it isnt identity#hplc-massspec · 2026-06-27no_chargebackmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-06-27no_chargebackunrelated but semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2, thats one data point#hplc-massspec · 2026-06-27fasting_insulinms/ms or it isnt identity#hplc-massspec · 2026-06-28lot_number_louthats a charge state#hplc-massspec · 2026-06-28karl_fischeris monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-06-28LC_MS_Lenasemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2026-06-28lot_number_loumonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2026-06-28lot_number_louif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2026-06-28logrotatefor the archive is monoisotopic or average mass the one on most certificates#hplc-massspec · 2026-06-30logrotateoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2026-06-30