Topic
Mass spectrometry
Page 2 of 15 — Monoisotopic versus average mass, multiply-charged ions and the arithmetic, and why MS/MS is the only real identity test.
Messages — page 2 of 15
homa_ir_hugoms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-03-10peak_splitif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-03-10peak_splitif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-03-10cat_on_the_trayoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-03-10HPLC_Hankdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant, ask me again in a month#hplc-massspec · 2025-03-16HPLC_Hankmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-03-16ferritin_faywhile im here i have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-03-19font_forensicsmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-03-21font_forensicsdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-03-21void_volumeif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-03-21mg_per_mlthats a charge state#hplc-massspec · 2025-03-21forty_unitsms/ms sequencing is the only thing i would call identity. everything else is circumstantial, ask me again in a month#hplc-massspec · 2025-03-21ms_ms_mirams/ms or it isnt identity#hplc-massspec · 2025-03-25lower_frequencytirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2025-03-25monoisotopicmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-03-26apnoea_down_twoms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-03-29baseline_driftmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-03-29baseline_driftthats a charge state#hplc-massspec · 2025-03-29void_volumei have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-03-29blank_rundeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-03-30amsterdam_aliquotms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-03-30HPLC_Hankms/ms or it isnt identity#hplc-massspec · 2025-03-30step_one_siansorry to jump in if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-03-30void_volumeis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-04-01food_noise_offi have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-04-01food_noise_offslightly off topic but ms/ms sequencing is the only thing i would call identity. everything else is circumstantial#hplc-massspec · 2025-04-01plus_sixteendoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-04-01LC_MS_Lenadoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-04-08cat_on_the_traymonoisotopic and average diverge more the bigger the molecule. say which one you are quoting, i think#hplc-massspec · 2025-04-08cat_on_the_trayoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-04-08peak_splittirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, still working it out#hplc-massspec · 2025-04-12peak_spliti have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-04-12typosquat_tayoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-04-12typosquat_tayok so monoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-04-12vialkeeperthats a charge state#hplc-massspec · 2025-04-12cold_chain_cmdrdeamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant#hplc-massspec · 2025-04-14alt_ast_alitirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5#hplc-massspec · 2025-04-15alt_ast_alithats a charge state#hplc-massspec · 2025-04-15relabel_watchis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-04-15acetate_ashsemaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2#hplc-massspec · 2025-04-19void_volumeis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-04-19week_zerodoes ms/ms actually prove identity or just make it very likely#hplc-massspec · 2025-04-20salt_bridgedeamidation converts an asparagine to an aspartate and adds about 1 Da. one dalton on a 4000 Da peptide is invisible on a…#hplc-massspec · 2025-04-20week_zero1 Da does something to retention time?#hplc-massspec · 2025-04-20c18_columnms/ms sequencing is the only thing i would call identity. everything else is circumstantial, from memory#hplc-massspec · 2025-04-26batch_banditmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-04-26truncation_truif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-04-26truncation_truis monoisotopic or average mass the one on most certificates#hplc-massspec · 2025-04-26alcohol_hitstirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, from memory#hplc-massspec · 2025-04-26truncation_trums/ms or it isnt identity#hplc-massspec · 2025-04-26alcohol_hitsif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic#hplc-massspec · 2025-04-26LC_MS_Lenawhile im here i have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-04-28LC_MS_Lenathats a charge state#hplc-massspec · 2025-04-28karl_fischerif somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result#hplc-massspec · 2025-05-01karl_fischeri have a number at about a third of what i expected, is that a charge state#hplc-massspec · 2025-05-01fake_trackingms/ms sequencing is the only thing i would call identity. everything else is circumstantial, ask me again in a month#hplc-massspec · 2025-05-01apnoea_down_twoif the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic, n of 1…#hplc-massspec · 2025-05-03area_percentoxidation is about plus 15.99 Da and is usually methionine or tryptophan#hplc-massspec · 2025-05-03area_percenttirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5 the honest position is that hobby-level interpretation…#hplc-massspec · 2025-05-04area_percentmonoisotopic and average diverge more the bigger the molecule. say which one you are quoting#hplc-massspec · 2025-05-04