Table 3.

Lowest quantitation limit of tryptophan metabolites by LC-MS method.

Quantitation limit (µM)	Tryptophan	Kynurenic acid	Kynurenine	Xanthurenic acid	Anthranilic acid	Indoxyl sulfate	Indoxyl acetate
	0.010	0.001	0.016	0.005	0.013	0.100	0.005