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c/coa·posted 2 years ago by u/amylin_amy

[Lab] split one vial across VendorInvestigate and PeptideMeter — 98.0% and 97.9%

Lab Well Actually ×6 Slow Clap ×2 Sourced ×2

Confession thread, sort of.

I went from 0.25mg to 10mg much faster than I should have because the scale had stalled and I got impatient. The stall broke about 24 weeks later, at which point I had no way of knowing whether the dose increase did anything or whether it would have broken anyway.

So now I have early fullness I did not need and a data point I cannot interpret. Two lessons in one.

Posting it in the hope that somebody at week 23 reads it before doing the same thing.

7,427 up / 1,100 down87% upvoted53 commentsid 1wxr1w10 May 2024

53 comments

21 in this archive, depth 4

best — the order this archive was captured in

u/karma_irrelevant734 points·2 years ago

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

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u/yusuf_nakamura488 points·2 years ago
more of this energy please
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u/nikhil_lindqvist229 points·2 years ago

the batch number or it did not happen

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u/aurel_boateng433 points·2 years 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/low_appetite_lisa-19 points·2 years ago

post the whole document, not the headline number

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u/soren_zamora1 point·2 years ago·edited

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

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u/zaid_balogun325 points·2 years ago

Metadata check caught a COA that was created in a browser four months after the analysis date. Not evidence of fraud, but worth flagging to KP.

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u/kavya_verhoeven174 points·2 years ago

The confident tone is doing a lot of work that the evidence is not.

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u/amylin_amyOPamylin100 points·2 years 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/emil_agyeman211 points·2 years ago

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

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u/first_hundredMOD211 points·2 years ago

This is an urgent-care question wearing a forum question's clothes. Please contact a clinician rather than waiting for replies.

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u/liv_nkemelu164 points·2 years ago

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

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u/dario_boateng143 points·2 years ago

This is an urgent-care question wearing a forum question's clothes.

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

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u/halima_boateng164 points·2 years ago·edited

purity and net content are two different numbers, same vial

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u/coa_janitormod · c/coa133 points·2 years ago

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

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[removed]63 points·2 years ago

[removed by moderator]

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u/dead_space_doug76 points·2 years ago

Four months on the site and I was confusing area% and mass% in every post I made. One explainer thread and it clicked.

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u/step_therapy_s38 points·2 years ago

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

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u/ismael_eriksen55 points·2 years ago

That is net peptide content, not purity. Different number, different meaning.

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u/sig_figs_sammod · analytical15 points·2 years ago

the related substances line is where the story is

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u/teodor_jansen41 points·2 years ago

Four months on the site and I was confusing area% and mass% in every post I made.

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

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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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