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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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