you need more sample for identity than for purity. plan for that when you post it
#hplc-massspec 2025-11-30
Sunday13 messages4 participantstimes are UTC
Highlights from this day
- tarpit_tam — tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5 23:33
- melb_meniscus — quick one does ms/ms actually prove identity or just make it very likely deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant 23:53
- melb_meniscus — while im here if the lab reports area percent without stating the wavelength, the number is less useful than it looks, for what its worth 23:54
retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily, ask me again in a month
run a blank
a shoulder on a peak is information, and usually bad information
ms/ms or it isnt identity
tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
M = 4113.6
[M+2H]2+ = (4113.6 + 2.02) / 2 = 2057.8
[M+3H]3+ = (4113.6 + 3.02) / 3 = 1372.2
observed 1372.3 -> consistentask for the trace
show me the spectrum
do the arithmetic
i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
is uv at 214 or 280 better for peptides
quick one does ms/ms actually prove identity or just make it very likely
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
while im here if the lab reports area percent without stating the wavelength, the number is less useful than it looks, for what its worth