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c/coa·submitted 2 years ago by u/tomas_lehtinen

[Discussion] can we stop arguing about related substances until somebody posts a number

Discussionbranch of 8 comments

I have had 17 orders now and I keep a table, so here is the honest summary rather than a vibe. Material has been consistent. Communication has not. Shipping has varied by about 4 days on nominally the same lane, which matters more in summer than in February. The independent number came back 96.8% against a claimed…

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8 comments, started 2 years ago
u/sig_figs_sammod · analytical73 points·2 years ago

Every time this gets posted it hits the front page and every time someone has to re-explain it.

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u/tomas_lehtinenOP39 points·2 years 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/katrin_girard18 points·2 years ago

axis labels included, always

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u/noor_cardoso14 points·2 years ago

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

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u/tomas_lehtinenOP6 points·2 years ago

Sent one vial to PeptideMeter and VendorInvestigate. 96.8% and 99.1%. Cost me more than the vial did and I would do it again.

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u/cesar_ivaturi24 points·2 years 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/soren_nkemelu22 points·2 years ago

axis labels included, always

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u/janek_ferrari16 points·2 years ago

PDF metadata is checkable in fifteen seconds

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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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