c/coa wiki

What this community is for

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.

c/coa was created on 18 Aug 2023 and currently has 71,200 members and 130 captured submissions. It sits in the busiest tier of the site, which mostly affects how fast a question gets answered rather than how well.

Rules, and why each exists

Community rules come first, then the six site-wide rules that apply everywhere on GLP Research Hub. Community rules are enforced by the moderators listed at the bottom of this page; site rules are enforced by everyone.

1. Post the full document. Cropped COAs that hide the batch number or date get removed.
2. Redact your own name and order id, not the vendor's batch details.
3. No "is this good?" without saying what the compound and claimed purity are.

And the site rules, which are short on purpose:

1. Independent community. Nobody here sells anything, and anyone who tries is banned.
2. Not medical advice. Describe what you did; never prescribe to a stranger.
3. Claims need evidence. Batch numbers, dated screenshots, independent test reports, or a citation.
4. No referral links, discount codes or affiliate URLs. Permanent ban, no appeal.
5. No contact handles, wallet addresses or tracking numbers — they identify people.
6. Be recognisably decent. Disagree hard, insult nobody.

Terms you will see

Vocabulary that turns up constantly in c/coa. Each links to the topic page, which collects every submission that touches it.

• COA — certificate of analysis — a lab report on a specific batch.
• certificate of analysis — a lab report on a specific production batch, of variable completeness.
• purity — usually area% from a UV chromatogram: how much of what the detector saw was product.
• area percent — the main peak as a fraction of total UV absorbance. Not a mass measurement.
• batch — a single production run; the unit a COA actually describes.
• related substances — impurities close enough to the product to show up near its peak.
• water content — residual moisture, by Karl Fischer or loss on drying; eats into net content.

Start here

The twelve highest-scoring submissions in this community. Not necessarily the most correct — the most agreed-with, which is a different thing, and worth remembering when you read them.

1. [Vendor] WXT vs JEEP on the same compound, same month — both cleared 97.0% — 15k points, 38 comments, 2 years ago
2. [Vendor] GL Biochem vs GGPeps on the same compound, same month — both cleared 97.5% — 14k points, 51 comments, 2 years ago
3. purity is the most under-discussed thing on this board — 13k points, 66 comments, 2 years ago
4. why does nobody talk about water content — 13k points, 63 comments, 1 year ago
5. [Meta] the area percent rule is doing its job and people should stop complaining — 11k points, 58 comments, 1 year ago
6. [Lab] FGP BPC — PeptideMeter came back 99.6% against a claimed 99.0% — 11k points, 28 comments, 1 year ago
7. how much of what we believe about batch actually comes from purity threads — 10k points, 52 comments, 1 year ago
8. [Question] COA — what am I missing here — 9.8k points, 25 comments, 2 years ago
9. reading area percent threads from 2024 and half of it aged badly — 9.2k points, 33 comments, 2 years ago
10. help me understand batch, I have read the wiki twice — 9.2k points, 43 comments, 1 year ago
11. purity — 9 things I got wrong before I got it right — 8.3k points, 43 comments, 1 year ago
12. [Discussion] the area percent advice in here is 2 years out of date — 8.2k points, 34 comments, 2 years ago

Asked constantly

• is 96.8% area% actually fine or am i being sold a rounding error
• PDF metadata says the file was created in a browser. is that normal?
• which fields turn a COA from a specification into a result
• is 96.8% area% actually fine or am i being sold a rounding error
• which fields turn a COA from a specification into a result
• [Question] vendor COA says 99.2%, my Janoshik came back 97.4%. who is wrong
• the area percent question that gets asked weekly, answered properly
• help me understand water content, I have read the wiki twice
• [Question] certificate of analysis — what am I missing here
• [Meta] proposal — a flair for water content posts

If your question is on that list, read the answers there first. If it is not, ask it — that is what the community is for, and "this has been asked" is only a helpful reply when it comes with a link.

Who runs this

Moderation here is done by volunteers who also post as normal members. They are not clinicians, not vendors, and not paid.

• u/coa_janitor — c/coa mod. If your COA screenshot is cropped above the batch number I will ask you to repost it.
• u/purity_pedant — Pedantry is a public service when milligrams are involved.
• u/coa_collector — I have 1,100 COAs in a folder structure that would frighten you. Ask before you order.
• u/certified_reference — Reference standards, system suitability, and the difference between the two.
• u/first_hundred — Member #63. The c/coa rules were my idea and I regret nothing.