Skip to content

1.9k

c/coa·posted 21 days ago by u/emeka_beaulieu

[Question] vendor COA says 99.2%, my Janoshik came back 97.4%. who is wrong

Question Receipts ×4 Cold Box ×2

vendor COA says 99.2%, my Janoshik came back 97.4%. who is wrong, and before anyone asks: same batch throughout, single submission, no cherry-picking between services.

The relevant figures are 99.2% and 97.4%, and they come from the same log I have kept the whole time.

Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.

Sent one vial to Medutest and PeptideMeter. 99.4% and a claimed 98.5%. Cost me more than the vial and I would do it again.

I will update this if the picture changes rather than quietly leaving it up.

3,083 up / 1,188 down72% upvoted14 commentsid 1vchro8 Jul 2026

14 comments

5 in this archive, depth 2sorted by:

best — the order this archive was captured in

u/priya_palacios0 points·20 days ago

The PDF creation date being later than the analysis date is usually a re-issue or a re-export. It is worth one question and it is not evidence of anything on its own.

replysharereportpermalink

u/emeka_beaulieuOP1 point·19 days ago

the related substances line is where the story is

replysharereportpermalink

u/yusuf_nakamura1 point·19 days ago

Same view. GL Biochem prints the column and the gradient, which means somebody could actually reproduce the run.

replysharereportpermalink

u/nadia_fonseca-36 points·20 days ago

water content is on there and everyone skips it

replysharereportpermalink

u/coa_collectorMOD1 point·20 days ago·edited

Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.

replysharereportpermalink

About c/coa

How to read a certificate of analysis and what it does and does not tell you. Area% versus mass%, identity versus quantity, water content, related substances, acetate counterions, and the difference between a vendor-supplied COA and an independent test on the vial you actually received.

71kmembers

130submissions

Aug 2023created

submissions / month, last year

Janoshik Analytical

Independent HPLC and mass spec. The number you get is the number they found.

janoshik.com Sponsored

GL Biochem (Shanghai)

Custom peptides and amino acids direct from the manufacturer since 1998. ISO 9001 / cGMP. Batch COA every order.

More in c/coa

1[Vendor] WXT vs JEEP on the same compound, same month — both cleared 97.0%15k points · 38 comments
2[Vendor] GL Biochem vs GGPeps on the same compound, same month — both cleared 97.5%14k points · 51 comments
3purity is the most under-discussed thing on this board13k points · 66 comments
4why does nobody talk about water content13k points · 63 comments
5[Meta] the area percent rule is doing its job and people should stop complaining11k points · 58 comments
6[Lab] FGP BPC — PeptideMeter came back 99.6% against a claimed 99.0%11k points · 28 comments

c/coa rules

Post the full document. Cropped COAs that hide the batch number or date get removed.
Redact your own name and order id, not the vendor's batch details.
No "is this good?" without saying what the compound and claimed purity are.
Independent community. Nobody here sells anything, and anyone who tries is banned.
Not medical advice. Describe what you did; never prescribe to a stranger.
Claims need evidence. Batch numbers, dated screenshots, independent test reports, or a citation.
No referral links, discount codes or affiliate URLs. Permanent ban, no appeal.
No contact handles, wallet addresses or tracking numbers — they identify people.
Be recognisably decent. Disagree hard, insult nobody.

Full rules and how they are enforced →

Moderators

u/coa_janitor u/purity_pedant u/coa_collector u/certified_reference u/first_hundred

Volunteers. Unpaid, unaffiliated, and reachable through modmail only.

Before you read on

Several compounds discussed on GLP Research Hub are sold for research use only and are not approved for human use anywhere. Nothing here is medical advice and none of it is written by your clinician. If a post reads like an instruction, treat it as a description of what one stranger did.

Full disclaimer →