the Janoshik question that gets asked weekly, answered properly
the Janoshik question that gets asked weekly, answered properly. It is the sort of thing everyone half-believes and nobody writes down. BCH BPC, batch matched the paperwork, Janoshik came back 99.6% against a claimed 99.0%. Paid for it myself, posting it because the log is only worth anything if people do. Chain 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 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.
Right, and a point or two between services is ordinary. It is agreement, and every month somebody posts it as a scandal.
This. The trend across separate lots is the number that tells you about a process rather than a vial.
Push back: three tests on one lot is one lot. It tells you about that lot and almost nothing about the next one.
Disagree that this is a discrepancy. 98.7% against a claimed 98.5% is inside ordinary inter-lab variance in either direction.