whats the void volume peak, is that always solvent
#hplc-massspec 2026-02-28
Saturday38 messages8 participantstimes are UTC
Highlights from this day
- VialBot — Digest for the week of 2026-01-26 has been published. 13:12
- freeze_thaw — you need more sample for identity than for purity. plan for that when you post it 14:00
- nine_nine_one — is uv at 214 or 280 better for peptides 14:19
- peak_split — monoisotopic and average diverge more the bigger the molecule. say which one you are quoting 16:58
- alcohol_hits — right so my peak has a shoulder on it, what does that usually mean 17:03
ms/ms or it isnt identity
plus 16 is oxidation
thats a charge state
Testing queue: 5 submissions open, 86 awaiting dispatch.
i asked VendorInvestigate for the raw trace and they sent it. that is the right answer to that question
Digest for the week of 2026-01-26 has been published.
😂6🤝17
coming back to this baseline is drifting badly, is that the column or the mobile phase
ok so whats a plus one dalton shift usually
do the arithmetic
you need more sample for identity than for purity. plan for that when you post it
peptidemeter-summary-b-0114.pdf
2 pages · 827 KB · not retained in the public archive
🤝11💀8
plus 0.98 is deamidation
has anyone ever had a result where the mass was right and the purity was wrong
is uv at 214 or 280 better for peptides
🙏13⚠️1
a warm transit can put a visible degradant peak on a chromatogram. that is what 8 days at ambient does
ask for the trace
214nm sees the amide backbone so it sees everything. 280 only sees aromatics
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column
plus sixteen, is that always oxidation
if the lab reports area percent without stating the wavelength, the number is less useful than it looks
🧪2❤️1
thats the solvent peak
coming back to this is there any point running a blank if the sample is the question
integration difference
if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result
retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily
within inter-lab range
show me the spectrum
why do two labs integrate the same peak differently
monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
🔥13🙏6
retention time is a hint
right so my peak has a shoulder on it, what does that usually mean
vial-sg-1177-front.png
900 × 1200 · 551 KB · not retained in the public archive
🔥5📈6👀6
how do you spot a deletion in a sequence from mass alone
slightly off topic but truncations show as a mass deficit matching one or more residues. you need the sequence to say which
why does integration change the number so much
need more sample
while im here relative retention time against a standard is comparable between labs. absolute minutes are not
i was wrong about tailing factor. it is usually the injection or the pH, not the column