Cross-section

Epitalon by laboratory

The same compound measured by different laboratories on different gradients. Where the medians differ, the question is whether the material differed or the method did — and for Epitalon, with a class minimum gradient of 15 min, the method is a live explanation.

90 recordsmedian 99.56 %spec 99.0 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	42	30min	High	99.65	+0.00	99.65	ADEQUATE
Medutest	19	25min	Unit	99.71	+0.08	99.63	ADEQUATE
PeptideMeter	11	28min	High	98.93	-0.05	98.98	ADEQUATE
VendorInvestigate	9	32min	High	99.48	-0.11	99.59	ADEQUATE
Kestrel	6 n=6	15min	Unit	99.54	+0.24	99.30	ADEQUATE
Nordanalyt	3 n=3	35min	High	99.54	+0.02	99.52	ADEQUATE

Figure. Epitalon purity by contributing laboratory. Any offset between rows has two possible sources — a real difference in the material each laboratory happened to receive, and the laboratory's own bias — and this figure cannot separate them. The paired analysis that can is on inter-lab agreement.