is a tailing factor of anything specific a problem
#hplc-massspec 2025-04-01
Tuesday27 messages6 participantstimes are UTC
Highlights from this day
- madrid_mg — i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer 22:41
- food_noise_off — i was wrong about tailing factor. it is usually the injection or the pH, not the column 22:48
- food_noise_off — slightly off topic but ms/ms sequencing is the only thing i would call identity. everything else is circumstantial 22:56
- plus_sixteen — whats the void volume peak, is that always solvent 22:57
- plus_sixteen — how do you spot a deletion in a sequence from mass alone 23:18
nobody runs enough blanks, including me, ill dig out the number
plus 0.98 is deamidation
is monoisotopic or average mass the one on most certificates
is there any point running a blank if the sample is the question
i have a number at about a third of what i expected, is that a charge state
shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly
while im here is uv at 214 or 280 better for peptides
retention time is a hint
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
you need more sample for identity than for purity. plan for that when you post it
*that should say weekly
214nm sees the amide backbone so it sees everything. 280 only sees aromatics
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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unrelated but whats a normal gradient for a peptide this size
i was wrong about tailing factor. it is usually the injection or the pH, not the column
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why do two labs integrate the same peak differently
[edited]slightly off topic but ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
fridge-temps.csv
570 rows · not retained in the public archive
whats the void volume peak, is that always solvent
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co-elution is the failure mode that a beautiful single peak is most likely to be hiding
does ms/ms actually prove identity or just make it very likely
thats co-elution
if the lab reports area percent without stating the wavelength, the number is less useful than it looks, ask me again in a month
how do you spot a deletion in a sequence from mass alone
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show me the spectrum
thats the solvent peak
a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you