Cross-section

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

14 recordsmedian 99.57 %spec 98.5 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	10	30min	High	99.54	+0.00	99.54	ADEQUATE
Nordanalyt	2 n=2	35min	High	99.93, 98.81	+0.02	—	ADEQUATE
Medutest	1 n=1	25min	Unit	99.93	+0.08	—	ADEQUATE
VendorInvestigate	1 n=1	32min	High	99.93	-0.11	—	ADEQUATE
PeptideMeter	0	28min	High	—	-0.05	—	ADEQUATE
Kestrel	0	15min	Unit	—	+0.24	—	ADEQUATE

Figure. Oxytocin 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.