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

genuine question about purity that I am slightly embarrassed to ask

Lab Well Actually ×4 Clean Column ×2 Cold Box ×2

Quick one. Canada here.

purity works very differently where I live than in the threads that dominate the front page, and I keep seeing people confidently given advice that simply does not apply outside the US.

Specifics: the route I used took 24 weeks and cost roughly what I expected. The admin was worse than the cost. The thing that would have saved me the most time was knowing which document to ask for at the start.

Happy to answer questions from anyone in the same jurisdiction.

3,793 up / 816 down82% upvoted50 commentsid 1keq9z7 Jan 2025

50 comments

30 in this archive, depth 4

best — the order this archive was captured in

u/laila_yilmaz-9 points·1 year ago
four days. it took four days for me.
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u/priya_palacios1 point·1 year ago

chromatogram or it did not happen

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u/amylin_amyOPamylin1 point·1 year ago

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

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u/stablecoin_steve1 point·1 year ago

chromatogram or it did not happen

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u/tidy_vialdrawer_pls260 points·1 year ago

Three years on this site and the questions have not changed at all. Which is depressing or reassuring depending on the day.

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u/cato_achebe84 points·1 year ago

This is the "correlation is mechanism" thing again. You changed three variables at once.

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u/ignacio_silva139 points·1 year ago

PDF metadata is checkable in fifteen seconds

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u/amylin_amyamylin171 points·1 year ago

chromatogram or it did not happen

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u/spreadsheet_gremlindata199 points·1 year ago

Rodent data is rodent data. Dose scaling is not linear and the models tell you what to investigate, not what to expect.

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u/vito_chowdhury63 points·1 year ago

the batch number or it did not happen

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u/dario_vermeulen47 points·1 year ago

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

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u/certified_referenceQC134 points·1 year 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/yannick_haddad63 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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u/sofia_ferreira28 points·1 year ago

Cosigning. The batch number is load-bearing information.

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u/stablecoin_steve9 points·1 year ago·edited

axis labels included, always

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u/amylin_amyOPamylin157 points·1 year ago

the batch number or it did not happen

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u/dario_boateng112 points·1 year ago

Slight fix: the number was 99.2, not 99.1. Decimal point, but a fairly consequential one.

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u/amylin_amyOPamylin60 points·1 year ago

I am going to push back on this slightly.

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[removed]99 points·1 year ago

[removed by moderator]

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u/bastian_aalto78 points·1 year 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/reflux_report18 points·1 year ago

chromatogram or it did not happen

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u/vito_chowdhury21 points·1 year ago

post the whole document, not the headline number

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u/anya_correia7 points·1 year ago

Not convinced. The evidence does not support that reading.

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u/sofia_ferreira48 points·1 year 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/bastian_moreau37 points·1 year ago

Not to be pedantic but batch and batch are being used interchangeably and they are not interchangeable in real life.

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u/purity_pedantMOD33 points·1 year ago

Removed a chain here. The rule is one line long and it is not negotiable.

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u/chidi_demir17 points·1 year ago

PDF metadata is checkable in fifteen seconds

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u/alcohol_aversion19 points·1 year ago

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

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u/nikhil_lindqvist12 points·1 year ago

Strongly agree.

Yes, exactly this, and it is the bit that took me 84 weeks to accept.

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u/joaquin_ivaturi9 points·1 year 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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