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145
c/coa·posted 11 days ago by u/cesar_ivaturi

water content is on the COA and everyone skips it

COA

Right, the certificate of analysis question again, but with numbers this time.

I have 12 data points over 36 weeks. The pattern is consistent enough that I do not think it is chance, and boring enough that nobody is going to screenshot it, which is usually a good sign.

The thing I would flag for anyone new: the effect I am describing showed up at week 78, not week 32. People give up long before the interesting part.

Interested in whether this matches other people's logs or whether I am an outlier.

149 up / 4 down98% upvoted13 commentsid 1wqfs519 Jul 2026

13 comments

13 in this archive, depth 5

best — the order this archive was captured in

u/coa_collectorMOD30 points·9 days ago

Flair changed to match the content. Read the sidebar before posting next time and we are square.

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u/nadia_fonseca0 points·9 days ago

axis labels included, always

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u/liv_nkemelu29 points·10 days ago

Every time this gets posted it hits the front page and every time someone has to re-explain it.

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u/yara_antonsen9 points·10 days ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/elodie_yilmaz3 points·9 days ago

Disagree. What you are describing is consistent with water content, not with what you concluded.

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u/santiago_szabo20 points·10 days ago

Water content was 3.8%, acetate was 6.2%, purity was 99%, but net peptide was only 90% of the label weight. Perfectly honest, just chemistry.

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u/cesar_ivaturiOP13 points·9 days ago·edited

The COA I was holding said 96.8% area and I thought it was trash. Turns out the method was solid and the impurity profile was clean.

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u/milos_trevino4 points·9 days ago

chromatogram or it did not happen

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u/emil_agyeman-10 points·9 days ago

Disagree. What you are describing is consistent with related substances, not with what you concluded.

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[removed]22 points·10 days ago

[removed by moderator]

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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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