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4.
Quality Control
a)
Blanks of 50 mM ammonium formate need to bracket each calibration curve to enable
check for laboratory background and instrumental carryover. Background should be no
more than 5% of the signal for the lowest working standard.
b)
Calibration Curve – Calibration curves are set up to bracket the sample injections.
Calibration residuals (relative error from known concentration) are expected to be ≤ 20%
for pyridoxal and ≤ 8% for the other vitamins. A standard injection outside of this range
can be excluded with evidence of a standard preparation error in a single calibration level
leading to a high or low response for all vitamins or evidence of a one-off instrumental
error, such as a missed injection.
c)
Laboratory Control - NIST SRM 1849a, or current lot, serves as a control sample and should
be prepared and analyzed with each sample set. The control result for each analyte must
be within limits established by a control chart. By and large, the levels reported by this
method are within the NIST certified range because of the minute concentration of
phosphorylated vitamin forms in SRM 1849a.
F.
Calculations
1.
Vitamin Stock Solutions concentration calculation
[ ]
Vol
PSMW Vit
s
Stk
000 ,1
××× ×
=
Where,
[Vit]
Stk
:
Vitamin standard stock solution concentration, in μg/mL.
W
S
:
Weight of standard in mg.
M:
Moisture content correction factor for the standard, if applicable.
S:
Stoichiometric correction factor, if applicable.
P:
Purity of standard as defined by the manufacturer.
1,000:
Units conversion factor, from mg to µg.
Vol:
Dissolution volume in mL.
2.
Calculation of vitamin concentrations in the Mixed Working Standard (MWS)
mL
Vol
Vit
Vit
Stk
MWS
10
] [
] [
×
=
Where,
[Vit]
MWS
:
Vitamin concentration in the Mixed Working Standard in ng/mL.
[Vit]
Stk
:
Concentration of Vitamin Stock Standard in μg/mL
Vol:
Volume of stock solution added to MWS in μL.
3.
Calculation of Working Standard concentration
Candidates for 2016 Method of the Year
195