does ms/ms actually prove identity or just make it very likely
#hplc-massspec 2025-10-12
Sunday16 messages4 participantstimes are UTC
Highlights from this day
- non_scale_win — sorry to jump in i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer 17:58
- bac_water_bill — if the lab reports area percent without stating the wavelength, the number is less useful than it looks, someone check my working 18:39
- tenpence — i was wrong about tailing factor. it is usually the injection or the pH, not the column, take that with a pinch of salt 19:32
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
plus 0.98 is deamidation
the first peak is the solvent. it is always the solvent, ill dig out the number
✅1
quick one a certificate with a number and no chromatogram is asking you to trust the integration you cannot see
tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
sorry to jump in i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
do the arithmetic
if the lab reports area percent without stating the wavelength, the number is less useful than it looks, someone check my working
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
ok so truncations show as a mass deficit matching one or more residues. you need the sequence to say which
a shoulder on a peak is information, and usually bad information
i was wrong about tailing factor. it is usually the injection or the pH, not the column, take that with a pinch of salt
19:35tenpence pinned a message to this channel
plus sixteen, is that always oxidation
ok so do you trust an area percent from a shallow gradient