Table 1.

UHPLC retention times (RT), negative ion electrospray MS/MS selected reaction monitoring (SRM) transitions, collision energies (CE), and concentrations (ng/mL) of standards spiked into blank human serum for calibration curves^a

				Spiked concentrations (ng/mL)
Analyte	RT (min)	SRM transition m/z	CE (V)	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)	(11)
Silychristin	1.9	481 → 125 481 → 325	29 22	1.2	2	4	8	16	32	64	128	256	512	1024
Silydianin	2.4	481 → 179 481 → 125	26 31	1.2	2	4	8	16	32	64	128	256	512	1024
Silybin A	5.1	481 → 125 481 → 301	28 21	0.4	2	4	8	16	32	64	128	256	512	1024
Silybin B	5.5	481 → 125 481 → 301	29 21	0.4	2	4	8	16	32	64	128	256	512	1024
Isosilybin A	6.9	481 → 125 481 → 453	29 20	0.4	2	4	8	16	32	64	128	256	512	1024
Isosilybin B	7.2	481 → 125 481 → 453	27 19	0.4	2	4	8	16	32	64	128	256	512	1024
d4-Daidzein	3.6	257 → 212 257 → 136	31 39

^aThe first SRM transition of each milk thistle flavonolignan was used as the quantifier while the second SRM transition was used as a qualifier in the UHPLC-MS/MS assay.