[Lab] four vendors, same compound, same week, one test each
Right: four vendors, same compound, same week, one test each. I paid for this one myself, nobody sent me anything, and the receipts are in the comments.
QSC BPC, batch matched the paperwork, PeptideMeter came back 98.6% against a claimed 98.0%. Paid for it myself, posting it because the log is only worth anything if people do.
Split one vial between PeptideMeter and VendorInvestigate. The two numbers were within half a point of each other and I stopped worrying about which lab to trust.
How to build a series that means something, if you are going to spend money on testing anyway.
Three tests on one lot tells you about your measurement. Three tests on three lots, spread over a year, tells you about a process. The second is the one worth paying for and it costs the same.
Buy small, keep the batch numbers, send one vial per lot, and post each one with the claim next to it. After four or five you have something no individual review can give you: a band, a direction and a date range. That is what the source pages are made of.
Ask me anything specific. Anything general I will probably get wrong.
best — the order this archive was captured in
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.
Sent a vial in specifically to check a supplier’s claim after a good experience. It matched. Boring result, worth logging.
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.
Did the vial lot match the paperwork lot?
Right, and a point or two between services is ordinary. It is agreement, and every month somebody posts it as a scandal.
Correction: that is the claimed figure, and the measured one is the higher of the two in your own screenshot.
How many separate lots does your series cover?
FGP came back 98.6% on a claimed 98.0%, which is agreement not a discrepancy
a result with no batch number is about a vial nobody can identify
I would not post that as a finding. It is a single result and the template asks you to say so.
Merged with the other thread on the same batch so the results sit together.
Agreed — the template exists because a result without the batch and the claim is unanchored.
one result is a data point, agreement between two services is evidence
Small fix — same supplier, different lot. The two rows in the log are not the same batch.
Tested three lots over a year rather than three vials from one lot. Cost the same and told me something completely different.
Inter-lab variance on this assay runs roughly a point either way, driven mostly by gradient and integration. Two results inside that band agree; they do not disagree quietly.
This. The trend across separate lots is the number that tells you about a process rather than a vial.
Kept every report as a PDF with the batch in the filename. Two years in, it is the most useful folder I own.
Area percent and net peptide content are different measurements and most reports give one. Quote which, or the comparison downstream is meaningless.
post the claim next to the result or the number floats
First result I ever posted here got asked for the batch number and the claim. Fair, and my posts have been better ever since.
That service reports area percent by default. Worth stating, since the thread has been comparing it to a mass figure.
Disagree that this is a discrepancy. 97.9% against a claimed 97.5% is inside ordinary inter-lab variance in either direction.
Disagree that this is a discrepancy.
Disagreeing with this line: that gap is ordinary variance, not a contradiction between the lab and the certificate.
inter-lab variance runs a point or two, plan your outrage accordingly
- 1Inter-lab variance on this assay runs roughly a point either way, driven…10 comments in this branch · started by u/camila_kowalski
- 2Right, and a point or two between services is ordinary. It is agreement, and…6 comments in this branch · started by u/crp_curious