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c/coa·posted 1 year ago by u/meera_sandvik

what would you tell week-1 you about related substances

Explainer Clean Column ×8 Cold Box ×1 Sourced ×1

Trying to settle this properly because the thread from last year went in circles.

The claim: certificate of analysis matters. The counter-claim: it is measurement error. Both sides have been asserting it confidently for about 24 months without either producing anything.

What would actually settle it is 21 people measuring the same thing the same way. I have started; my numbers are below. They lean one way but not strongly enough for me to declare victory.

If you have data, post the data. If you have an opinion, flair it as an opinion.

15,665 up / 5,955 down72% upvoted25 commentsid 1u8d1w8 Jul 2025

25 comments

10 in this archive, depth 4

best — the order this archive was captured in

u/anders_kuusela1.7k points·1 year 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/aurel_boateng-7 points·1 year ago

axis labels included, always

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u/nadia_fonseca1 point·1 year ago

the counterion is part of the mass you paid for

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[removed]1 point·1 year ago

[removed by moderator]

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u/step_therapy_s1 point·1 year ago

post the whole document, not the headline number

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u/alcohol_aversion1.5k points·1 year ago

Sceptical. If this were true we would see it reflected in the data and we do not.

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u/yara_antonsen652 points·1 year ago
more of this energy please
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u/anya_correia263 points·1 year ago

the related substances line is where the story is

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u/joaquin_ivaturi169 points·1 year 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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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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Independent HPLC and mass spec. The number you get is the number they found.

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