[Below Spec] 88% is not "basically fine" and i am tired of that reply
Short version of the title, which is already short: 88% is not "basically fine" and i am tired of that reply. Longer version underneath.
Figures up front so nobody has to dig: 88%.
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.
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.
If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.
best — the order this archive was captured in
Nudging rather than removing: the standard template is in the sidebar and this post is missing the batch field.
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.
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.
Correction: that is the claimed figure, and the measured one is the higher of the two in your own screenshot.
Inter-lab variance on this assay runs roughly a point either way, driven mostly by gradient and integration.
Adding the boring but useful bit: say whether you paid for it. It is the basis of the whole log.
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.
if you are going to test, test the thing you actually received
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.
Small fix — same supplier, different lot. The two rows in the log are not the same batch.
Yes. Two services on the same batch is the strongest thing an individual member can produce, and it is not expensive.
[removed by moderator]
What was the claim on the certificate you are comparing against?
That service reports area percent by default. Worth stating, since the thread has been comparing it to a mass figure.
results without method are gossip with decimals
net peptide content if the report gives it, and say which you are quoting
Agreed — the template exists because a result without the batch and the claim is unanchored.
Which service, and did you pay for it yourself?
Correcting myself: I quoted net peptide content against somebody else’s area percent. Not a comparison.
the trend across lots is worth more than any single figure
the trend across lots is worth more than any single figure
Agreed — and two services on one batch is the strongest thing any of us can produce individually.
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.
area percent unless the report says otherwise
split a vial across two services once and you will never argue about ground truth again
WXT came back 98.7% on a claimed 98.5%, which is agreement not a discrepancy
Have now spent more on testing than on some of the orders. No regrets — the log is the reason I can buy without agonising.
Agreed on quoting the claim alongside the result. Half the arguments here are two people comparing to different reference numbers.
- 1Yes. Two services on the same batch is the strongest thing an individual…13 comments in this branch · started by u/mei_cardoso