Table 5.

Precision studies of vitamin D₃ and MK-7 by HPLC and UHPLC.

Analyte	Repeatability (n = 5)		Reproducibility (n = 5)
	Concentration (μg mL−1)	Concentration found (μg mL−1) ± SEM; RSD	Concentration found (μg mL−1) ± SEM; RSD
			Day 1	Day 2	Day 3
Technique: HPLC
Vitamin D3	45.0	44.94 ± 0.23; 1.45	44.92 ± 0.81; 0.61	44.93 ± 0.52; 1.41	45.21 ± 0.42; 1.03
	50.0	50.41 ± 0.11; 0.42	49.95 ± 1.22; 0.84	50.65 ± 0.42; 1.00	50.42 ± 0.73; 1.19
	55.0	54.98 ± 0.36; 1.70	55.49 ± 0.73; 1.20	55.43 ± 0.32; 0.80	55.44 ± 0.43; 1.01
MK-7	45.0	44.92 ± 0.22; 1.92	44.98 ± 0.32; 2.30	45.24 ± 0.23; 2.23	45.24 ± 0.12; 1.98
	50.0	49.46 ± 0.31; 1.02	50.58 ± 0.12; 1.72	50.25 ± 0.12; 1.97	50.25 ± 0.11; 1.29
	55.0	54.91 ± 0.41; 0.72	54.92 ± 0.33; 2.11	55.36 ± 0.43; 1.88	55.31 ± 0.31; 0.98
Technique: UHPLC
Vitamin D3	45.0	45.15 ± 0.12; 1.46	45.45 ± 0.22; 1.02	45.01 ± 0.02; 1.19	44.63 ± 0.21; 0.54
	50.0	50.12 ± 0.22; 0.80	50.33 ± 0.62; 0.79	50.33 ± 0.11; 0.42	49.41 ± 0.31; 0.39
	55.0	55.34 ± 0.32; 0.84	55.41 ± 0.32; 0.78	54.98 ± 0.21; 0.42	55.19 ± 0.12; 0.74
MK-7	45.0	45.21 ± 0.41; 1.20	45.23 ± 0.92; 1.67	45.04 ± 0.11; 1.64	45.23 ± 0.13; 2.21
	50.0	50.52 ± 0.51; 0.93	50.29 ± 0.11; 1.08	50.51 ± 0.21; 1.08	50.53 ± 0.21; 1.23
	55.0	55.31 ± 0.71; 0.97	55.61 ± 0.31; 0.54	55.29 ± 0.21; 0.81	55.31 ± 0.22; 1.35

SEM: standard error mean; RSD: relative standard deviation.