Table 3.

Limits of quantitation (LOQ), linear dynamic range, and intra- and inter-day precision in the determination of vitamin D metabolites from plasma

Component	LOQ pg/mL (plasma)	Linearity (pg/μL)	r 2	Intra-day (%CV)	Inter-day (%CV)
24,25-(OH)2 D3	n/aa	0.1–300	0.9995	4.1	6.8
1,25-(OH)2 D3	20	0.2–50	0.9990	3.9	6.1
1,25-(OH)2 D2	10	0.1–50	0.9992	2.2	6.2
25-OH D3	10	2.5–300	0.9999	3.8	5.8
25-OH D2	10	2.5–300	0.9996	1.6	3.7

No LOD was given because of the lack of a commercial deuterated standard. 24,25(OH) D3 and 1,25(OH) D3 were similar, and the LOQ is estimated to be similar to that of 1,25(OH) D3

^a24,25-(OH)₂ D₃ was quantified using D6-25-OH D₂ as internal standard