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c/coa·posted 3 months ago by u/sofia_ferreira

[Question] New Zealand — has anyone got a straight answer on certificate of analysis

Question Receipts ×6

Long-ish post, sorry. tl;dr at the bottom.

I have been tracking COA against eGFR for 33 weeks because I could not find anyone who had. The correlation is weaker than I expected, which is itself mildly interesting given how confidently people link the two in here.

Caveats up front: one person, one lab, one assay, no control, and I changed my training in the middle of it, which was stupid.

tl;dr: probably real, definitely smaller than the threads imply, and not worth reorganising your week around.

284 up / 7 down98% upvoted26 commentsid xre38o1 Apr 2026

26 comments

18 in this archive, depth 6

best — the order this archive was captured in

u/teodor_lokken26 points·3 months ago

Inter-lab variance on this kind of assay is routinely 1–2 points. Different column, different gradient, different integration.

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u/katrin_girard16 points·3 months ago

PDF metadata is checkable in fifteen seconds

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u/yusuf_nakamura5 points·3 months ago

This is the correct framing. The COA structure matters as much as the number.

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u/clara_danquah-9 points·3 months ago

Water content on the document? That affects your concentration math.

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u/emeka_chowdhury16 points·3 months ago

You have restated the marketing copy. What is the actual substance here.

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u/tuva_aalto10 points·3 months ago

PDF metadata is checkable in fifteen seconds

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u/clara_danquah3 points·3 months ago

PDF metadata is checkable in fifteen seconds

Adding to this: COA is doing more work than the comment implies.

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u/soren_nkemelu1 point·3 months ago

no "is this good?" without saying what the compound and claimed purity are

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u/priya_palacios1 point·3 months ago

What is the method line say? Not the technique, the actual method.

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u/clara_restrepo2 points·3 months ago

PDF metadata is checkable in fifteen seconds

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u/amira_dumitru1 point·3 months ago·edited

Not to be pedantic but area percent and related substances are being used interchangeably and they are not interchangeable in real life.

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u/yusuf_nakamura1 point·3 months ago

Not to be pedantic but area percent and related substances are being used interchangeably and they are not interchangeable in real life.

Disagree on that part. 98.7% and 98.3% on the same vial is normal.

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u/ismael_eriksen1 point·3 months ago

Edit to your parent would help — the concentration you quoted assumes one scenario and you have written another above it.

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u/cato_achebe4 points·3 months ago

redact your own name, not the vendor's batch details

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[removed]3 points·3 months ago

[removed by moderator]

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u/sofia_danquah2 points·3 months ago

post the whole document, not the headline number

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u/first_hundred8 points·3 months ago

the counterion is part of the mass you paid for

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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.

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