Cross-section

Selank 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 Selank, with a class minimum gradient of 15 min, the method is a live explanation.

102 recordsmedian 99.59 %spec 99.0 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	47	30min	High	99.63	+0.00	99.63	ADEQUATE
PeptideMeter	21	28min	High	99.53	-0.05	99.58	ADEQUATE
Medutest	11	25min	Unit	99.66	+0.08	99.58	ADEQUATE
Nordanalyt	9	35min	High	99.42	+0.02	99.40	ADEQUATE
VendorInvestigate	8	32min	High	99.72	-0.11	99.83	ADEQUATE
Kestrel	6 n=6	15min	Unit	99.37	+0.24	99.13	ADEQUATE

Figure. Selank 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.