Fortnightly digest · 2024-10-21 → 2024-11-03
charge states, and the panic that a third of a number causes
The instrument channel got properly technical for the first time. A member posted a spectrum, announced that their peptide had the wrong mass, and was walked through multiply-charged ions until the number made sense. The explanation that followed is one of the clearest things in the archive, and it exists because somebody was confidently wrong in public.
2.4Kmessages
99day logs
3channels noted
5notes
What happened
- A peak at roughly a third of the expected mass is usually a triply-charged ion rather than a degraded peptide, and the arithmetic takes ten seconds.
- Retention time alone is not identity, because two different peptides can co-elute and a single number cannot distinguish them.
- Deamidation at plus one dalton and oxidation at plus sixteen were introduced as the two shifts worth learning to recognise on sight.
- HPLC_Hank posted an annotated spectrum and asked people to find the impurity themselves before he labelled it, which worked better than a lecture.
- Somebody claimed a supplier had run mass spec without ever producing a spectrum, and the channel called that a claim rather than a result.
Channels this fortnight
#hplc-massspecReversed phase, area %, charge states, +1 and +16. Bring a spectrum.0 logs · 0 msgs#coa-readingPurity is not assay. A COA without a lot number is a picture.2 logs · 65 msgs#test-resultsPost the report, the lot number, and where you bought it. One data point is one data point.2 logs · 36 msgs
Most-reacted messages in this fortnight
Pulled from the logs, not hand-picked. Each links to the exact message.
logrotatei keep three suppliers on rotation so a stock gap never becomes a problem, take that with a pinch of salt47 reactions · #vendor-talk · 2024-10-22cagri_curiousdid anybody find a difference between QYB and pharmacy at the same 1542 reactions · #semaglutide · 2024-10-22oasis_olanot a peptide42 reactions · #oral-glp1 · 2024-10-26no_appetite_niawhats a sensible maintenance dose after a year at treatment dose40 reactions · #dosing-titration · 2024-10-28nine_nine_oneabdomen two inches out from the navel, avoiding anything that has been injected in the last month39 reactions · #injection-technique · 2024-10-28marrow.moda seizure letter is usually the end of it. you have lost the parcel and that is almost always the whole consequence37 reactions · #shipping-customs · 2024-10-24swab_dry_firstfor the archive the plateau hit me at 30 weeks and moved again about a month later without a dose change37 reactions · #semaglutide · 2024-10-30underfill_umaunrelated but 20mg in 2ml is 10mg/ml. 1mg is 10 units, 2mg is 20 units, easy35 reactions · #reconstitution · 2024-11-03
Busiest logs in this fortnight
#tirzepatide · 2024-10-26€185 for a 2 vial is roughly what ive paid for the last year49 msgs#tirzepatide · 2024-10-2710 was enough48 msgs#vendor-talk · 2024-10-30they improved47 msgs#vendor-verification · 2024-10-27what does not count: the supplier certificate alone, a screenshot, a referral link, or a friend who says…46 msgs#side-effects · 2024-11-01it does stop44 msgs#dosing-titration · 2024-10-26is there any actual reason to escalate every 4 weeks other than the trial did it43 msgs#semaglutide · 2024-10-30my Medutest report on the SGN vial came back 97.4 against a certificate saying 98.643 msgs#retatrutide · 2024-11-03stopped for 25 months and restarted at half my old dose, the ramp was easier second time43 msgs#vendor-talk · 2024-10-29if three people give you three different suppliers, that is because all three work. pick one and test it42 msgs#dosing-titration · 2024-11-03is there any actual reason to escalate every 4 weeks other than the trial did it40 msgs#coa-reading · 2024-10-26no lot number on this certificate, does that make it worthless38 msgs#injection-technique · 2024-10-27fresh pin38 msgs