thats the solvent peak
#hplc-massspec 2026-05-25
Monday22 messages6 participantstimes are UTC
Highlights from this day
- chlorhex — quick one how do you spot a deletion in a sequence from mass alone integration choices move the number by a few tenths easily. that is most of your inter-lab variance 18:59
- two_four_ceiling — right so if the lab reports area percent without stating the wavelength, the number is less useful than it looks 19:10
- sgp_subq — update from 16 months ago: switched to asking for the chromatogram rather than the number and it changed everything 19:18
- VialBot — Verification log updated: QST — evidence added, status unchanged. 19:28
semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
thats co-elution
quick one how do you spot a deletion in a sequence from mass alone
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
relative retention time against a standard is comparable between labs. absolute minutes are not
integration difference
right so if the lab reports area percent without stating the wavelength, the number is less useful than it looks
why do two labs integrate the same peak differently
update from 16 months ago: switched to asking for the chromatogram rather than the number and it changed everything
plus 0.98 is deamidation
⚠️17📉3
ask for the trace
ms/ms or it isnt identity
is there any point running a blank if the sample is the question
19:27chlorhex pinned a message
Verification log updated: QST — evidence added, status unchanged.
👍10📈7
nobody runs enough blanks, including me
run a blank
❤️5🧊7🤝1
need more sample
baseline is drifting badly, is that the column or the mobile phase
retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily
is uv at 214 or 280 better for peptides
a shoulder on a peak is information, and usually bad information