no lot no certificate
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#coa-reading 2026-01-18
Sunday44 messages9 participantstimes are UTC
Highlights from this day
- tarpit_tam — **area%** is a ratio. the main peak divided by the sum of all peaks the detector saw, times 100. it has no units of mass in it anywhere. an empty vial with 0.2mg of… 22:03
- tarpit_tam — **assay** or content is a quantity. mg of peptide per vial, measured against a reference standard of known concentration. that is the number that tells you your dose 22:10
- tarpit_tam — it is the most common failure mode we see. by a distance 22:21
- tarpit_tam — worked example, two made-up vials off the same label 22:22
is area percent the same thing as how many mg are in the vial
a lab that reports "greater than 98%" rather than a number is telling you they did not integrate carefully
i keep every certificate in a dated folder and compare them. two suppliers had not changed their template since 2019
i asked WWB for the method and they sent it. that alone put them ahead of most
good certificate actually
does anyone keep a folder of certificates to compare over time
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coming back after 10 months, has the pinned reading guide changed
same chromatogram
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why do some certificates report to one decimal and some to two
is sterility tested as part of a normal purity certificate
update on the earlier thing my 15mg vial weighed more than 10mg of powder, is the certificate lying
is there a standard layout or does every lab do their own
whats the related substances table actually telling me
gross mass on a jewellery scale plus the water content is enough to catch most underfills
does purity by hplc at one wavelength miss things
right. area% vs assay. i am going to say this once properly and then link people here forever
area% is a ratio. the main peak divided by the sum of all peaks the detector saw, times 100.
it has no units of mass in it anywhere.
an empty vial with 0.2mg of pure peptide in it can report 99.5% area%.
so can a 10mg vial. the number does not distinguish them
wait what
assay or content is a quantity. mg of peptide per vial, measured against a reference standard of known concentration. that is the number that tells you your dose
this is why the community started paying for quantity tests and not just purity tests
and why the going joke is that a 99% pure 6mg vial labelled 10mg is a very clean rip-off
so purity high, quantity low is possible
it is the most common failure mode we see. by a distance
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worked example, two made-up vials off the same label
Two hypothetical vials, both labelled 10 mg
vial A vial B
HPLC area% 99.4 % 98.1 %
assay 9.8 mg 6.9 mg
KF water 4.1 % 5.0 %
net peptide ~9.4 mg ~6.6 mg
vial A: boring, correct, slightly wet
vial B: 'purer than 98%!' and 30 % short on dose
the area% column cannot see the differenceok that actually landed
my Sangon-sourced semaglutide came back 8.4mg on a 10mg label, purity 98.9
janoshik-J24-11407-sgn-sema.pdf
2 pages · 188 KB · not retained in the public archive
8.4 is a real result and not a scandal. 16% under is bad but it is in underfill territory not fake-product territory
*8.42 to be exact
for what it is worth 8.4 could be underfill, could be moisture, could be counterion, could be all three stacking
how would you tell them apart
you cannot, from that report alone. quantity tests give you a number not a cause
the JEEP Peptides lots i tested last spring were consistently 9.6 to 10.1 which is the tightest fill i have personally paid to see
n of 4 though. i am not claiming anything
noted and appreciated
22:58pinned the area% vs assay explanation to the top of this channel
so if a vendor only ever posts purity and never quantity
then they are advertising the cheaper test. purity tests cost less than quantity tests, that is most of the story
TFC used to post purity only, now some of their sheets carry content. that is movement in the right direction whatever else you think of them
is there any reason a vendor would post purity only that isnt shady
yes. quantity needs a reference standard of the same peptide and for newer compounds those are expensive or awkward to source. it is a real constraint
hm, i had assumed it was always cost-cutting
sometimes it is. both things are true and you cannot tell which from outside
thank you, genuinely. i have read about ten pages that never said any of this
most of what is written about this is written by people selling something