Table 1.

Validation parameters. Low-, medium- and high-QCs were 3, 8 and 16 ng/mL, respectively.

Analyte	Linear Range (ng/mL)	r2	LOD (ng/mL)	LOQ (ng/mL)	Accuracy (%CV)			Inter-Day Precision (%CV)			Intra-Day Precision (%CV)			Recovery (%)			Matrix Effect (%)
					lQC	mQC	hQC	lQC	mQC	hQC	lQC	mQC	hQC	lQC	mQC	hQC	lQC	mQC	hQC
Etazene	1–20	0.995	0.25	0.5	8	21	11	12	18	4	15	7	13	99	89	84	88	108	97
Flunitazene	1–20	0.997	0.25	0.5	10	9	8	15	12	9	12	9	18	95	110	105	80	110	95
Isotonitazene	1–20	0.993	0.35	0.5	17	20	12	8	16	11	18	11	12	91	117	92	108	93	96
Protonitazene	1–20	0.992	0.35	0.5	18	15	16	3	5	2	11	12	16	93	92	99	112	108	101

Abbreviations: %CV, percent coefficient of variation; hQC, high-QC; LOD, limit of detection; LOQ, limit of quantification; lQC, low-QC; mQC, medium-QC; r², coefficient of determination.