#hplc-massspec 2025-08-17

Sunday19 messages4 participantstimes are UTC

Highlights from this day

two_ml_two — i was wrong about tailing factor. it is usually the injection or the pH, not the column 18:05
VialBot — New independent result logged — SWB, lot F-1330, purity 97.4% (PeptideMeter). 18:53
VialBot — Reminder for two_ml_two: dose day is today. Set 3 days ago. 19:43
monoisotopic — baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column, take that with a pinch of salt 20:20

i was wrong about tailing factor. it is usually the injection or the pH, not the column

😂1✅1

tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5

ask for the trace

plus 16 is oxidation

🤝12

New independent result logged — SWB, lot F-1330, purity 97.4% (PeptideMeter).

deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant

how do you spot a deletion in a sequence from mass alone

Reminder for two_ml_two: dose day is today. Set 3 days ago.

show me the spectrum

*VendorInvestigate not the other one

i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer, ymmv

has anyone ever had a result where the mass was right and the purity was wrong

thats the solvent peak

if the lab reports area percent without stating the wavelength, the number is less useful than it looks

baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column, take that with a pinch of salt

update from 17 months ago: switched to asking for the chromatogram rather than the number and it changed everything

214nm sees the amide backbone so it sees everything. 280 only sees aromatics

retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily

22:53tenpence pinned a message