Development of isotope dilution-liquid chromatography tandem mass spectrometry for the accurate determination of vitamin K1 in spinach and kimchi cabbage

Journal of Analytical Science and Technology

Table 2 Repeatability and reproducibility of the developed ID-LC/MS/MS method. (A) Spinach and (B) kimchi cabbage

(A)
	Subsample No	ID-LC/MS/MS Results (mg/kg)
	Subsample No	trans-vitamin K₁	cis-vitamin K₁
Period 1	#1	24.26 ± 0.65^d	0.217 ± 0.014
	#2	23.80 ± 0.64	0.237 ± 0.012
	#3	24.59 ± 0.61	0.241 ± 0.018
	#4	24.14 ± 0.59	0.220 ± 0.009
	Average	24.2 ± 1.0	0.229 ± 0.004
	Standard deviation^a	0.33 (1.4%)	0.012 (5.3%)
	Average of total vitamin K₁^b	24.43
	Standard deviation combined	0.33 (1.4%)
	Expanded uncertainty combined	1.1 (4.3%)
Period 2	#1	24.12 ± 0.94	0.218 ± 0.023
	#2	24.57 ± 0.97	0.235 ± 0.043
	#3	24.51 ± 0.97	0.233 ± 0.024
	#4	24.56 ± 0.96	0.234 ± 0.056
	Average	24.4 ± 1.3	0.230 ± 0.008
	Standard deviation	0.22 (0.88%)	0.008 (3.6%)
	Average of total vitamin K₁	24.67
	Standard deviation combined 1.69%	0.22 (0.90%)
	Expanded uncertainty combined	1.29 (5.3%)
Period 3	#1	24.22 ± 0.91	0.250 ± 0.020
	#2	24.13 ± 0.89	0.242 ± 0.019
	#3	23.91 ± 0.86	0.247 ± 0.020
	#4	23.97 ± 0.88	0.247 ± 0.020
	Average	24.1 ± 1.0	0.243 ± 0.024
	Standard deviation	0.14 (0.60%)	0.008 (3.09%)
	Average of total vitamin K₁	24.30
	Standard deviation combined	0.15 (0.61%)
	Expanded uncertainty combined	1.0 (4.1%)
Average		24.23	0.23
Standard deviation among period^c		0.19 (0.80%)	0.008 (3.3%)

(B)
	Subsample No	ID-LC/MS/MS Results (mg/kg)
	Subsample No	trans-vitamin K₁	cis-vitamin K₁
Period 1	#1	13.39 ± 0.32	0.148 ± 0.013
	#2	13.630 ± 0.34	0.149 ± 0.006
	#3	13.81 ± 0.34	0.161 ± 0.014
	#4	13.31 ± 0.33	0.139 ± 0.008
	Average	13.53 ± 0.47	0.149 ± 0.008
	Standard deviation	0.23 (1.7%)	0.009 (6.0%)
	Average of total vitamin K₁	13.68
	Standard deviation combined	0.23 (1.7%)
	Expanded uncertainty combined	0.68 (5.0%)
Period 2	#1	13.68 ± 0.54	0.173 ± 0.009
	#2	13.58 ± 0.54	0.162 ± 0.013
	#3	13.61 ± 0.54	0.153 ± 0.011
	#4	13.56 ± 0.54	0.151 ± 0.011
	Average	13.61 ± 0.75	0.160 ± 0.010
	Standard deviation	0.005 (0.40%)	0.010 (6.2%)
	Average of total vitamin K₁	13.77
	Standard deviation combined	0.06 (0.46%)
	Expanded uncertainty combined	0.75 (5.5%)
Period 3	#1	13.29 ± 0.47	0.151 ± 0.024
	#2	13.35 ± 0.49	0.131 ± 0.014
	#3	13.43 ± 0.50	0.137 ± 0.011
	#4	13.28 ± 0.58	0.138 ± 0.014
	Average	13.34 ± 0.54	0.138 ± 0.014
	Standard deviation	0.067 (0.51%)	0.009 (6.59%)
	Average of total vitamin K₁	13.48
	Standard deviation combined	0.07 (0.49%)
	Expanded uncertainty combined	0.62 (4.6%)
Average		13.49	0.149
Standard deviation among period		0.16 (1.2%)	0.011 (7.4%)

^aThe value provided in parentheses indicates the relative standard deviation compared to the mean value
^bTotal vitamin K₁ is the sum of trans- and cis-vitamin K₁
^cStandard deviation of the results among three time periods, indicating the method’s reproducibility
^dThe number after “ ± ” is the expanded uncertainty of the proceeding value with the 95% confidence level