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Fonterra Co-operative Group
Page 5
Table 1: Samples used during method validation
Sample
Code
Fortified
Child Formula Powder
00847RF00
No
Infant Elemental Powder
00796RF
No
Adult Nutritional RTF
(1)
High Protein
00821RF00
No
Adult Nutritional RTF High Fat
00820RF00
No
Infant Formula RTF, Milk-Based
EV4H2Q
No
NIST SRM
(2)
1849a
CLC10-b
D
3
Infant Formula Powder Partially Hydrolysed Milk-Based
410057652Z
D
3
Infant Formula Powder Partially Hydrolysed Soy-Based
410457651Z
D
3
Toddler Formula Powder Milk-Based
4052755861
D
3
Infant Formula Powder Milk-Based
4044755861
D
3
Adult Nutritional Powder Low Fat
00859RF00
D
3
Child Formula Powder
00866RF00
D
3
Infant Elemental Powder
00795RF
D
3
Infant Formula Powder FOS/GOS-Based
50350017W1
D
3
Infant Formula Powder Milk-Based
K16NTAV
D
3
Infant Formula Powder Soy-Based
E10NWZC
D
3
Infant Formula RTF Milk-Based
EV4H2R
D
3
Adult Nutritional RTF High Protein
00730RF00
D
3
Adult Nutritional RTF High Fat
00729RF00
D
3
In-house Reference
–
D
3
(1)
RTF = Ready-To-Feed
(2)
SRM = Standard Reference Material
Linearity
Within the working range, signal response will have a linear relationship to analyte concentration and the
extent of this range may be demonstrated. Regression calculations on their own are insufficient to establish
linearity and other tests are required to demonstrate linear detector response over the working range. They
can include a visual inspection of the linear regression line and residuals, as well as back calculation of
standard concentrations.
Linearity was evaluated by analysis of 6-level calibration standards on three different days. Regression and
residuals plots of the ratios of the concentrations of analyte vitamin D with stable isotope labelled vitamin D
against the ratios of peak areas of analyte vitamin D with stable isotope labelled vitamin D were prepared.
Linearity for vitamin D
2
and vitamin D
3
was demonstrated by the calculation of correlation coefficients, back-
calculation of standard concentrations (Tables 2
–
3), and visual evaluation of regression and residuals plots
(Figures 1
–
6).
The average range for vitamin D
2
in linearity standards was 0.3
–
59.1 ng mL
-1
, which is equivalent to a
sample powder concentration of 0.3
–
65 μg hg
-1
(0.04
–
7.3 μg hg
-1
RTF) which extends beyond both the
VitD-18 (February 2016)
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