[Discussion] we are measuring batch at the wrong time and calling it noise
we are measuring batch at the wrong time and calling it noise — a position I have arrived at slowly and would like tested.
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.
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.
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.
Happy to answer the boring questions. Those are usually the ones worth asking.
best — the order this archive was captured in
What a result posted here is actually worth, and how to make yours worth more.
A single figure with no batch identifier is about a vial nobody can locate. Add the batch and it becomes about a lot. Add the claimed figure from the certificate and it becomes a comparison. Add the service and the date and it becomes reproducible. Say that you paid for it yourself and it becomes independent.
Five extra fields, thirty seconds of typing, and the difference between a comment and a row in the log that will still be useful in three years.
Have now spent more on testing than on some of the orders. No regrets — the log is the reason I can buy without agonising.
Have now spent more on testing than on some of the orders.
Disagreeing with this line: that gap is ordinary variance, not a contradiction between the lab and the certificate.
Small fix — same supplier, different lot. The two rows in the log are not the same batch.
Do you have the trace, or only the summary?
vendor, compound, batch, service, result — that is the template
A series across separate lots estimates a process. Repeat tests on one lot estimate the measurement. Both are useful and they answer different questions.
area percent unless the report says otherwise
area percent unless the report says otherwise
piotr_nascimento is right that the band matters more than the peak. Consistency across lots is the finding.
That service reports area percent by default. Worth stating, since the thread has been comparing it to a mass figure.
the trend across lots is worth more than any single figure
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.
Date of analysis anchors the result to a manufacturing period. A two-year-old result is evidence about two years ago and should be read that way.
BCH came back 98.3% on a claimed 98.0%, which is agreement not a discrepancy
if you are going to test, test the thing you actually received
Agreed — the template exists because a result without the batch and the claim is unanchored.
Fourth lot from the same supplier in the log now and the band has been tight the whole way. That consistency is the actual finding.
Merged with the other thread on the same batch so the results sit together.
How many separate lots does your series cover?
date of analysis matters as much as the number
Area percent and net peptide content are different measurements and most reports give one. Quote which, or the comparison downstream is meaningless.
Area percent and net peptide content are different measurements and most reports give one.
Agreed — and two services on one batch is the strongest thing any of us can produce individually.
Correction: that is the claimed figure, and the measured one is the higher of the two in your own screenshot.
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.
say whether you paid for it yourself
Kept every report as a PDF with the batch in the filename. Two years in, it is the most useful folder I own.
Kept every report as a PDF with the batch in the filename.
This is why the template has a batch field. Without it the result is about a vial nobody can identify.
Split one vial between Medutest and PeptideMeter. The two numbers were within half a point of each other and I stopped worrying about which lab to trust.
- 1Area percent and net peptide content are different measurements and most…8 comments in this branch · started by u/anders_vermeulen
- 2Chain of custody is why member-funded testing is worth more than a supplied…6 comments in this branch · started by u/camila_mensa