612 / 670
gas flow
᧶
11 L/min
᧷
carrier gas
᧶
N
2
᧷
collision gas
᧶
high-purity N
2
᧷
the MRM parameters are
shown in Table 3.
Table 3. MRM Parameters of PTAD derivatives
Compound
Parent ion, m/z
Daughter ion, m/z
Fragmentor, V Collision voltage, eV
VD2-PTAD
572.2
298
380
12
572.2
161
380
42
VD3-PTAD
560.2
298
380
12
560.2
161
380
38
ID3 -PTAD
563.2
301
380
12
Note
᧶
VD2-PTAD, VD3-PTAD, and ID3-PTAD are the PTAD derivatives of VD2, VD3, and ID3, respectively.
3 Single-laboratory validation
3.1 Linearity
The calibration curves determined in 3 independent days were shown in Table 4. The results
showed a good linearity within the analytical range of 0.5
̚
100 ng/mL, with the correlation
relationship greater than 0.9997. The slope RSD of the 3 calibration curves was lower than 2%,
indicating a good repeatability.
Table 4. Calibration curves determined in 3 independent days.
Day
VD2
VD3
Calibration curve
R
2
Slope RSD Calibration curve
R
2
Slope RSD
1 y=0.950657x-0.015080 0.9998
1.50%
y=0.961485x-0.024003 0.9999
1.63%
2 y=0.962971x-0.022250 0.9999
y=0.993221x-0.031660 0.9998
3 y=0.934650x-0.030390 0.9997
y=0.975156x+0.004472 0.9997
3.2 Accuracy and Precision
3.2.1The determination of NIST SRM1849a
The reference sample NIST SRM1849a was analyzed continuously in 6 independent days
with 6 replicates in each day, and the testing results were shown in Table 5. There was no VD2
being detected in NIST SRM 1849a, and the average value of the testing results of VD3 in this
reference sample was 105
μg/kg
, which was within the certificate of analysis (CoA) range of 111
± 17
μg/kg
. Both within- (6 replicates) and between-day (6 days) RSD values were lower than 3%.
The results indicated a good accuracy and precision of this method.
Table 5. The measurement precision of VD3 in NIST SRM 1849a
Replicates
VD3 test results,
μg/kg
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
1
106
110
102
106
106
105
2
104
103
101
109
105
105
3
112
105
98
104
105
106
4
110
104
99
106
103
105
VitD-17 (February 2016)
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