Table A1.

HPLC-MS/MS validation data: Regression equation, limit of detection (LOD), and limit of quantification (LOQ).

Compound	Regression Equation 1				LOD 2 [ng/mL]	LOQ 2 [ng/mL]
	${\mathit{y}}_{\mathit{i}}=\mathit{a}\times {\mathit{c}}_{\mathit{i}}+\mathit{b}$
	Slope (a)	Offset (b)	R2	Lin. Test
α-KBA	164.7	1130.8	0.9996	linear	6.0	21.1
β-KBA	170.9	366.8	0.9999	linear	4.8	17.0
α-AKBA	408.6	1000.1	0.9997	linear	2.3	8.5
β-AKBA	420.2	1002.5	0.9997	linear	3.7	13.4

¹ Regression equations of 10-point calibration (1–1000 ng/mL); y_i: peak area of the corresponding compound [cps]; c_i: concentration of the corresponding compound [ng/mL]; linearity (lin.) test with 1% level of significance. ² LOD and LOQ according to DIN 32645 on the basis of a 7-point calibration (1–100 ng/mL).