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c/coa·posted 4 months ago by u/andres_restrepo

help me understand purity, I have read the wiki twice

Question Sourced ×6 Slow Clap ×2

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 10 months without either producing anything.

What would actually settle it is 31 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.

1,522 up / 267 down85% upvoted58 commentsid yvci0k10 Mar 2026

58 comments

27 in this archive, depth 5

best — the order this archive was captured in

u/halima_boateng108 points·4 months ago·edited

The evidence standard in c/vendorvetting gets called too strict about once a month, and every time, the thread ends with the complainant agreeing.

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[removed]81 points·4 months ago

[removed by moderator]

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u/milos_trevino19 points·4 months ago

the batch number or it did not happen

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u/milos_vanhecke6 points·4 months ago

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

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u/india_generic_g12 points·4 months ago

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

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u/andres_restrepoOP5 points·4 months ago

Slight fix: the number was 99.0, not 98.9. Decimal point, but a fairly consequential one.

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u/yara_antonsen85 points·4 months ago·edited

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

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u/karma_irrelevant-26 points·4 months ago

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

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u/elodie_yilmaz29 points·4 months ago

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

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u/wanjiru_varga76 points·4 months ago

Tested the GLB raw material and a reseller vial side-by-side. Same purity claim, different impurity profiles. Handling matters.

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u/andres_restrepoOP45 points·4 months ago

the counterion is part of the mass you paid for

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u/valeria_girard34 points·4 months ago

Cosigning. The batch number is load-bearing information.

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u/india_generic_g0 points·4 months ago

the related substances line is where the story is

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u/coa_collectorarchivist1 point·4 months ago

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

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u/tove_ogunleye1 point·4 months ago

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

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u/wrong_network_w1 point·4 months ago

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

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u/anecdata_annie59 points·4 months ago

Disagree. What you are describing is consistent with certificate of analysis, not with what you concluded.

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u/joaquin_ivaturi24 points·4 months ago

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

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u/certified_referenceQC13 points·4 months ago

the counterion is part of the mass you paid for

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u/yannick_haddad4 points·4 months ago

post the whole document, not the headline number

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u/rohan_steiner6 points·4 months ago

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

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u/spreadsheet_gremlindata5 points·4 months ago

purity and net content are two different numbers, same vial

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u/milos_trevino47 points·4 months ago·edited

What were the related substances listed individually?

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u/andres_restrepoOP19 points·4 months ago

Asked HJ for the batch-specific COA and they sent it within six hours, full document, batch number, date, everything. That is the baseline.

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u/isabela_nilsen49 points·4 months ago

Batch number and date of analysis? Both are load-bearing.

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u/janek_ferrari34 points·4 months ago·edited

The practical rule people converge on is 28 days at fridge temperature after first puncture, and that comes from the preservative, not the peptide.

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u/valeria_karlsen17 points·4 months ago

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

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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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c/coa rules
  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.
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  5. Not medical advice. Describe what you did; never prescribe to a stranger.
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