ISO/WD
© ISO 2013 – All rights reserved
11
i A’ Om’
O A’ im’
= iRf
(2)
where
im’
: is the mass fraction of FAME i in the calibration standard solution (5.19 or 5.20)
OA’
: is the peak area of C11:0 in the calibration standard solution chromatogram
Om’
: in the mass of C11:0 in the calibration standard solution (5.19 or 5.20)
iA’
: is peak area of FAME i in the calibration standard solution chromatogram
The variation between 3 injections is optimal when coefficients of variation are less than 2.
NOTE
The response factors calculated for C18:2 n-6 could be applied for C-18:2 CLA and that calculated for C18:3 n-3
cis could be applied for C18:3
trans
isomers.
10.1.2 Fatty acids on the product
Calculate the mass fraction of the individual components expressed in gFA
i
/100g product in the test sample by
using the following equation:
product
/100g i
gFA
=
m OA
100
(FA) iS iRF i A Om
(3)
where
Om
mass of C11:0 internal standard, in milligrams, added to the sample solution;
iA
: peak area of FAME i in the sample chromatogram;
iRF
: response factor, calculated according to 10.1.1;
) (iS
FA
: stoichiometric factor to convert FAME i to FA i (Annex B Table B.1);
OA
: peak area of C11:0 internal standard in the sample chromatogram;
m
: mass of test portion, in milligrams.
NOTE 1
The response factors RF
i
for C18:2 n-6
cis
can be used for C18:2 CLA and the response factor RF
i
for C18:3 n-3
cis
can be used for C18:3
trans
isomers.
NOTE 2
In case of fatty acids analysis carried out on fat extracted from foods, the mass of test portion
“m”
corresponds to
fat and not to the product. Consequently fatty acids results are expressed in gFA/100g fat and not in gFA/100g product with
this equation. Results obtained in gFA/100g fat could be then converted into gFA/100g product with the fat extraction value
determined with an appropriate validated extraction method. The declared fat value should not be used for the expression of
fatty acids on finished products..
10.1.3 Fatty acids on the total fat
Calculate the mass fraction of the individual components expressed in gFA
i
/100g fat in test sample by using the
following equation:
fat
/100g i
gFA
=
Fat %
100
product
/100g i
gFA
(4)
