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c/coa·posted 11 months ago by u/purity_pedant

[Lab] 7th independent test on WXT — 99.2% on a claimed 98.5%, and the trend is the interesting part

Lab Long Haul ×2 Cold Box ×1 Well Actually ×1

7th independent test on WXT — 99.2% on a claimed 98.5%, and the trend is the interesting part. That is the headline. The document, the batch and the service are below so you can argue with the method rather than with me.

Numbers, in the order they matter: 99.2% and 98.5%.

Asked ERP for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody.

Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for. A 99% pure acetate salt can still be about 85% peptide by mass.

Research-use-only material is not approved for human use and nothing here should be read as a recommendation to use it.

4,484 up / 722 down86% upvoted15 commentsid 1tydg75 Aug 2025
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15 comments

11 in this archive, depth 3

best — the order this archive was captured in

u/coa_collectorMOD568 points·11 months ago

Left up and flaired Explainer. This is the answer we keep linking, written properly.

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u/vito_chowdhury126 points·11 months ago

Ask what the stability statement was written against — temperature, light, and whether it was the lyophilised powder or the reconstituted solution. Those are three different claims.

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u/purity_pedantOPanalytical68 points·11 months ago

Does the lot on the vial match the lot on the page?

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u/chidi_demir341 points·11 months ago

I would not read a rounded figure as evasive. Plenty of documents round to one decimal as house style.

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[deleted]150 points·11 months ago

[deleted]

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u/tidy_vialdrawer_pls49 points·11 months ago

Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.

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u/purity_pedantOPanalytical106 points·11 months ago

Are the related substances itemised or is it a single total?

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u/amara_halonen277 points·11 months ago

My first certificate had a compound name, a percentage and a logo. I thought that was normal. It is not, and now I know what to ask for.

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u/wanjiru_varga-13 points·11 months ago

The PDF creation date being later than the analysis date is usually a re-issue or a re-export. It is worth one question and it is not evidence of anything on its own.

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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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