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848

help me understand below spec, I have read the wiki twice

Discussion Sourced ×8

Question in the title, detail here: help me understand below spec, I have read the wiki twice.

The template is vendor, compound, batch, service, claim, result, and who paid. Every one of those fields exists because a result missing it has been argued about here before.

Area percent and net peptide content are different measurements and most reports give one. Quote which, or the comparison downstream is meaningless.

A series across separate lots estimates a process. Repeat tests on one lot estimate the measurement. Both are useful and they answer different questions.

Ask me anything specific. Anything general I will probably get wrong.

1,134 up / 286 down80% upvoted40 commentsid 1pmiof19 Feb 2024

40 comments

24 in this archive, depth 4

best — the order this archive was captured in

u/crp_curious171 points·2 years ago

On inter-lab disagreement, which generates more heat here than anything else.

Two services running different gradients, integrating differently, at possibly different wavelengths, will not produce identical numbers on the same material. A point either way is ordinary. Half a point is close agreement.

The productive response to a gap that size is to post both results with both methods and let the log accumulate. The unproductive response is to pick the lower number, call it the truth, and open a dispute. Members have done the first for long enough now that the bands in the vendor tables are genuinely informative.

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u/yara_bakken58 points·2 years ago

area percent unless the report says otherwise

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u/camila_mensa16 points·2 years ago

What was the claim on the certificate you are comparing against?

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u/ravi_sandvik77 points·2 years ago

Disagree that this is a discrepancy. 98.3% against a claimed 97.5% is inside ordinary inter-lab variance in either direction.

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u/clara_weiss21 points·2 years ago·edited

Yes. Two services on the same batch is the strongest thing an individual member can produce, and it is not expensive.

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u/kavya_radich47 points·2 years ago

a result with no batch number is about a vial nobody can identify

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u/rina_sobczak114 points·2 years ago

If the report gives a mass spectrum as well as UV purity, say so. Identity and relative quantity are separate claims and the log tracks both.

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u/meera_sandvik49 points·2 years ago

MKM BPC, batch matched the paperwork, VendorInvestigate came back 97.9% against a claimed 97.0%. Paid for it myself, posting it because the log is only worth anything if people do.

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u/georgi_chowdhury58 points·2 years ago·edited

net peptide content if the report gives it, and say which you are quoting

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u/hedda_aguirre16 points·2 years ago

That reading assumes area percent and net peptide content are the same number. They are not, and the report says which it is.

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u/ewan_marchand11 points·2 years ago

Yes — date of analysis, because a result from two years ago describes a different manufacturing month.

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u/cold_chromatogram_onlyOP55 points·2 years ago

results without method are gossip with decimals

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u/peptidemeter_patMOD91 points·2 years ago

Merged with the other thread on the same batch so the results sit together.

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u/bianca_demir69 points·2 years ago

First result I ever posted here got asked for the batch number and the claim. Fair, and my posts have been better ever since.

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u/stubborn_batchlist_only22 points·2 years ago·edited

Push back: three tests on one lot is one lot. It tells you about that lot and almost nothing about the next one.

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u/boots_or_bust18 points·2 years ago

say whether you paid for it yourself

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u/jarno_cabrera42 points·2 years ago

Cosigning on saying who paid. It is the whole basis on which this log is worth anything.

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u/ismael_nwosu-19 points·2 years ago

three lots beats three tests on one lot

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u/enzo_fonseca1 point·2 years ago

Agreed — the template exists because a result without the batch and the claim is unanchored.

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u/britta_boateng1 point·2 years ago

Agreed — the template exists because a result without the batch and the claim is unanchored.

Disagreeing with this line: that gap is ordinary variance, not a contradiction between the lab and the certificate.

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u/mateusz_mensah-24 points·2 years ago

post the claim next to the result or the number floats

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u/clara_weiss1 point·2 years ago

split a vial across two services once and you will never argue about ground truth again

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u/endotoxin_elliemicro1 point·2 years ago

Same. The BCH results have been sitting in a tight band across lots, which is the useful shape.

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u/usp_appendixcompendial1 point·2 years ago

Chain of custody is why member-funded testing is worth more than a supplied certificate: the vial tested is the vial that arrived at a member’s door.

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