Table 3.

Extraction recovery (R%) of the investigated metabolites at three concentration levels in serum

Metabolite	Concentration (ng/ml)	R%	r2	LOD (ng/ml)	LLOQ (ng/ml)
24,25(OH)2D3	6	92	0.9992	0.1	0.5
	25	85
	45	97
1,25(OH)2D3	0.8	95	0.9992	0.2	0.4
	5	81
	9	99
3β-25(OH)D3	8	93	0.9992	0.05	2
	50	90
	90	93
3α-25(OH)D3	5	94	0.9990	0.02	0.1
	12	88
	18	93
D3	8	89	0.9977	—	0.7
	50	82
	90	85

Linearity was expressed as coefficient of determination (r2), LOD, and LLOQ.