214nm sees the amide backbone so it sees everything. 280 only sees aromatics
#hplc-massspec 2025-05-07
Wednesday19 messages4 participantstimes are UTC
Highlights from this day
- combo_cai — plus sixteen, is that always oxidation 20:54
- combo_cai — oxidation is about plus 15.99 Da and is usually methionine or tryptophan 21:08
- combo_cai — coming back to this how do you spot a deletion in a sequence from mass alone 21:32
- group_buy_gwen — semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2 21:51
- combo_cai — i asked VendorInvestigate for the raw trace and they sent it. that is the right answer to that question 21:57
is uv at 214 or 280 better for peptides
is monoisotopic or average mass the one on most certificates
plus sixteen, is that always oxidation
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integration choices move the number by a few tenths easily. that is most of your inter-lab variance
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
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relative retention time against a standard is comparable between labs. absolute minutes are not
shallow gradient
vial-a-2601-front.png
900 × 1200 · 463 KB · not retained in the public archive
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
i was wrong about tailing factor. it is usually the injection or the pH, not the column, we shall see
coming back to this how do you spot a deletion in a sequence from mass alone
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right so is a tailing factor of anything specific a problem
semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
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a certificate with a number and no chromatogram is asking you to trust the integration you cannot see, take that with a pinch of salt
if the lab reports area percent without stating the wavelength, the number is less useful than it looks
i asked VendorInvestigate for the raw trace and they sent it. that is the right answer to that question
fridge-temps.csv
175 rows · not retained in the public archive
how would a truncation sequence show up
retention time is a hint
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