Cross-section

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

48 recordsmedian 98.88 %spec 97.0 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	23	30min	High	98.80	+0.00	98.80	ADEQUATE
Nordanalyt	9	35min	High	98.84	+0.02	98.82	ADEQUATE
PeptideMeter	6 n=6	28min	High	98.81	-0.05	98.86	ADEQUATE
Medutest	5 n=5	25min	Unit	98.89	+0.08	98.81	ADEQUATE
VendorInvestigate	4 n=4	32min	High	99.03	-0.11	99.14	ADEQUATE
Kestrel	1 n=1	15min	Unit	98.37	+0.24	—	ADEQUATE

Figure. NAD+ 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.