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692
c/coa·posted 1 months ago by u/tove_ogunleye

why does nobody talk about purity

COA Well Actually ×4

Right, the COA question again, but with numbers this time.

I have 8 data points over 20 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 43, not week 92. People give up long before the interesting part.

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

970 up / 278 down78% upvoted32 commentsid raial9 Jun 2026

32 comments

23 in this archive, depth 5

best — the order this archive was captured in

u/mikkel_correia69 points·1 months ago

Water content matters more than people think. If a vial is carrying residual moisture, your "10mg" is not 10mg of peptide.

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u/anecdata_annie34 points·1 months ago

Titration speed is a side-effect dial far more than an efficacy dial.

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u/nikhil_lindqvist31 points·1 months ago·edited

axis labels included, always

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u/andres_restrepo21 points·1 months ago

PDF metadata is checkable in fifteen seconds

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u/laila_wojcik5 points·1 months ago

No. This is the kind of confident post that gets copied into a screenshot and repeated for years. Where is the evidence.

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u/low_appetite_lisa-3 points·1 months ago

Yeah, 96.8% area is not the problem, the missing impurity breakdown is the problem.

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u/laila_wojcik12 points·1 months ago

Respectfully this is a sample of one presented as a finding.

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[deleted]4 points·1 months ago

[deleted]

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u/tove_ogunleyeOP2 points·1 months ago

area% is not mass%, and here is exactly why it matters

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u/sofia_danquah9 points·1 months ago

Dead space in the needle hub holds a small but non-trivial volume. On low-volume draws that can be several units.

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u/emeka_beaulieu6 points·1 months ago

area% is not mass%, and here is exactly why it matters

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u/tomas_lehtinen4 points·1 months ago

Yeah, 96.8% area is not the problem, the missing impurity breakdown is the problem.

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u/tove_ogunleyeOP3 points·1 months ago

the method line is doing real work, not just window dressing

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u/stablecoin_steve6 points·1 months ago

Slight fix: the number was 98.7, not 98.1. Decimal point, but a fairly consequential one.

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u/tove_ogunleyeOP7 points·1 months ago

What were the related substances listed individually?

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u/priya_palacios2 points·1 months ago

axis labels included, always

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u/tomas_lehtinen6 points·1 months ago

the method line is doing real work, not just window dressing

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u/neha_erdogan5 points·1 months ago·edited

the method line is doing real work, not just window dressing

Disagree on that part. 99.3% and 93.7% on the same vial is normal.

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u/emeka_beaulieu2 points·1 months ago

Strongly agree. Mass% and area% are answering different questions on the same document.

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u/bastian_aalto4 points·1 months ago

Mechanistically the bit that matters is related substances. It explains most of the early profile and a decent chunk of the outcome.

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u/valeria_girard1 point·1 months ago

Mechanistically the bit that matters is related substances.

Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.

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u/dead_space_doug6 points·1 months ago

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

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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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