Cross-section

L-Glutathione (reduced) 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-Glutathione (reduced), with a class minimum gradient of 15 min, the method is a live explanation.

129 recordsmedian 99.33 %spec 98.5 %

Laboratory	Reports	Gradient	MS resolution	Median purity %	Published bias (pp)	Bias-adjusted	Method suitability
Janoshik	64	30min	High	99.22	+0.00	99.22	ADEQUATE
Medutest	20	25min	Unit	99.35	+0.08	99.27	ADEQUATE
PeptideMeter	19	28min	High	99.39	-0.05	99.44	ADEQUATE
Nordanalyt	16	35min	High	99.41	+0.02	99.39	ADEQUATE
Kestrel	6 n=6	15min	Unit	99.39	+0.24	99.15	ADEQUATE
VendorInvestigate	4 n=4	32min	High	98.62	-0.11	98.73	ADEQUATE

Figure. L-Glutathione (reduced) 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.