Cross-section

L-Carnosine 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 L-Carnosine, with a class minimum gradient of 15 min, the method is a live explanation.

29 recordsmedian 99.07 %spec 99.0 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	12	30min	High	99.07	+0.00	99.07	ADEQUATE
Nordanalyt	5 n=5	35min	High	99.32	+0.02	99.30	ADEQUATE
PeptideMeter	4 n=4	28min	High	99.16	-0.05	99.21	ADEQUATE
Medutest	4 n=4	25min	Unit	99.93	+0.08	99.85	ADEQUATE
VendorInvestigate	3 n=3	32min	High	98.19	-0.11	98.30	ADEQUATE
Kestrel	1 n=1	15min	Unit	99.43	+0.24	—	ADEQUATE

Figure. L-Carnosine 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.