manual of methods for determining micronutrients in fortified foods

Where
PARAMETER EXPLANATION VALUE
mg std=
mg of USP standard weighed in reagents (6.e.1) ?
mL std
= mL of standard used in procedure step 7.b.3 ?
C std
=
concentration of USP vitamin A (as retinol) per USP certification
(mg/g)
PH std
= peak height or area of standard from chromatogram ?
10,000 = combined dilution factors for vitamin A standard 10,000
b. Using retinylpalmitate
Response factor for vitamin A (RF A
):
?
Where
Parameter Explanation Value
mg std=
mg retinyl palmitate weighed in reagent step (6.e.2) ?
mL std
= mL of standard used in procedure step 7.b.3 ?
P std
=
Percent purity certified by supplier (or determined), divided by
100
?
PH std
= peak height or area of standard from chromatogram ?
0.5458 = ratio of retinol to retinyl palmitate molecular weights 0.5458
500 = combined dilution factors and conversion from mg to µg 500
2. RF A
values of low, medium and high standards should agree with each other within 3% relative
since detector response should be linear across the concentration range used here. Average
of RF A
values calculated from high, medium, and low standards should be used for sample
quantitation.
3. Measure peak heights or areas corresponding to retinol in sample extracts. The 13-cis isomer
of retinol (eluting immediately before the all-trans isomer) might be present in some samples.
4. Calculate vitamin A content using the following formula:
Vitamin A, µg/g (as retinol) = RF A
x PH sam
x 100
w
Where:
PH sam
= total sample peak height or area of all-trans
100 = € dilution volume of sample
w = weight of sample in g
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