plus 0.98 is deamidation
#hplc-massspec 2025-12-18
Thursday18 messages5 participantstimes are UTC
Highlights from this day
- igf_one_ivy — i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer 18:09
- igf_one_ivy — if the lab reports area percent without stating the wavelength, the number is less useful than it looks 18:24
- blank_run — how much sample does a lab actually need for identity as well as purity 18:40
- assay_not_purity — baseline is drifting badly, is that the column or the mobile phase 19:17
- assay_not_purity — deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant 20:33
nobody runs enough blanks, including me
i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
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within inter-lab range
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if the lab reports area percent without stating the wavelength, the number is less useful than it looks
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retention time is a hint
follow up do you trust an area percent from a shallow gradient
a certificate with a number and no chromatogram is asking you to trust the integration you cannot see
how much sample does a lab actually need for identity as well as purity
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whats the void volume peak, is that always solvent
baseline is drifting badly, is that the column or the mobile phase
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my peak has a shoulder on it, what does that usually mean
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column
run a blank
ms/ms or it isnt identity
janoshik-c-4402.pdf
2 pages · 388 KB · not retained in the public archive
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
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tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
plus sixteen, is that always oxidation
update from 2 months ago: switched to asking for the chromatogram rather than the number and it changed everything, thats just me