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5

110

110

102

107

105

102

6

105

106

105

102

108

102

Mean value

, μg/kg

108

107

101

106

105

104

RSD

ˈ

%

3.01% 2.80% 2.35% 2.33% 1.51% 1.48%

Total average

, μg/kg

105

Within-day RSD

2.25%

Between-day RSD

2.36%

Total RSD

2.97%

3.2.2 VD2 recovery study in spiked NIST SRM 1849a

NIST SRM 1849a was used as the base matrix to conduct the VD2 recovery study. The spike

levels were 12, 50, and 250 ng of VD2

corresponding to 0.12, 0.5, and 2.5

μg

VD2/100 g

reconstituted or RTF samples, respectively. Each spike level was tested 6 times continuously in 6

independent days, and 2 replicates were done within each day. The testing results in Table 6

showed that the recoveries of VD2 at all spike levels were all within 101-103%, and the

within-day and between-day RSD values were all lower than 6%.

Table 6. Recovery of VD2 in spiked NIST SRM 1849a samples

Spike

level, ng

Day

Replicates

Average RSD

Total

average

Within-day

RSD

Between-day

RSD

Total

RSD

1

2

0.12

1

101% 101% 101% 0.36%

101% 1.78%

3.01% 3.47%

2

101% 101% 101% 0.30%

3

104% 105% 105% 1.14%

4

101% 101% 101% 0.22%

5

106% 98% 102% 5.52%

6

93% 97% 95% 3.12%

0.50

1

103% 92% 97% 8.52%

103% 4.04%

4.27% 5.23%

2

99% 103% 101% 2.88%

3

101% 95% 98% 4.02%

4

105% 111% 108% 4.10%

5

108% 104% 106% 2.56%

6

103% 106% 105% 2.17%

2.50

1

107% 99% 103% 5.60%

103% 3.64%

2.25% 4.05%

2

99% 100% 100% 0.77%

3

102% 102% 102% 0.48%

4

112% 99% 106% 8.40%

5

104% 107% 106% 2.27%

6

107% 101% 104% 4.32%

3.2.3 Recovery study of VD2 and VD3 in spiked samples with different matrices

Four powder (liquid) samples with different matrices were selected to conduct the recovery

study of VD2 and VD3. The background value of VD3 in each sample was determined as the

VitD-17 (February 2016)

FOR ERP USE ONLY

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