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G
olay
&
M
oulin
:
J
ournal of
AOAC I
nternational
V
ol
.
99, N
o
.
1, 2016
to four areas: (
1
) remarks regarding the collaborative study’s
organization (i.e., information, sample, schedule); (
2
) comments
about the procedure used for sample analysis; (
3
) statements
about insufficient information provided in the method (or
inconsistency); and (
4
) remarks about the method not being
well implemented in laboratory. In general, all comments were
positive with respect to the use of this complex chromatographic
method in routine analysis, which necessitates an experienced and
trained analyst. All comments were summarized and sent to the
ERP for review in July 2014 prior to receiving Final Action status.
The method has demonstrated its compliance with the
applicability statement of AOAC SMPR 2012.011 and has
been shown, in this collaborative study, to be suitable for the
analysis of fatty acids in selected food matrixes. The majority
of results provided for individual and groups of fatty acids
were in agreement with expectations (i.e., results gained with
proficiency tests and SLV).
Nevertheless, this kind of analytical method requires
particular attention for the chromatography part, which is the
source of principal differences observed in the results (i.e.,
response factors of the instrument, coelution, and wrong peak
identification and integration, but also errors in the reporting).
The accurate identification and quantification of each peak
corresponding to
trans
isomers is very important because
they can significantly impact the TFA sums. The C18:3
trans
isomers (having possibly two, three, or four different peaks
corresponding to
trans
isomers) are the most difficult category
of isomers to quantify in food matrixes due to possible coelution
with other fatty acids.
The global performance of the method is satisfactory because
RSD
r
and RSD
R
values for labeled fatty acids were below 85%
of limits fixed in the SMPR for all concentrations. RSD
R
values
were summarized separately for labeled fatty acids in SPIFAN
materials and ISO-IDF materials due to different expression
of results (Table 4). Results compared to the SMPR values are
shown in Table 5.
Conclusions
A multilaboratory collaborative study of AOAC First Action
Method
2012.13
“Determination of Labeled FattyAcids Content
in Milk Products and Infant Formula (and Adult/Pediatric
Nutritional Formula) by Capillary Gas Chromatography”
and ISO 16958:2015 | IDF 231:2015 was done. This method
was applied to representative dairy, infant formula, and adult/
pediatric nutritional formula products and demonstrated
acceptable reproducibility precision for all fatty acids (i.e.,
46 individuals and/or groups) analyzed for these categories of
products.
Recommendations
A detailed report summarizing the outcomes of this
collaborative study was submitted with the recommendation
that AOAC First Action Method
2012.13
be accepted as a
SPIFAN-endorsed AOAC Final Action Method. The AOAC
ERP evaluated the collaborative study data in September 2014
and endorsed the recommendation, which was subsequently
approved by the Official Methods Board in October 2014.
Table 3. Proposed limits for repeatability and
reproducibility values
Concentration, g/100 g Repeatability (RSD
r
) Reproducibility (RSD
R
)
<0.05 and ≥0.005
10
25
<0.005 and ≤0.001
15
40
Table 4. Results of the collaborative study
Fatty acid
SPIFAN materials
a
ISO-IDF materials
b
Range
RSD
R
, %
Range
RSD
R
, %
Min.
Max.
Min.
Max.
TFA (total)
0.006–0.027
21.31
42.47
0.008–5.056
8.69
32.92
SFAs
0.195–1.945
1.92
6.50
0.812–57.777
2.38
5.72
PUFAs
0.324–1.129
4.58
8.86
0.107–2.795
2.73
11.17
MUFAs
c
0.803–4.552
4.14
8.64
0.717–18.894
4.25
8.80
Omega-3 (ω-3)
0.055–0.121
5.32
8.40
0.022–0.637
4.47
11.68
Omega-6 (ω-6)
0.268–1.019
4.61
8.96
0.051–1.262
2.86
7.80
Omega-9 (ω-9)
0.799–4.543
4.14
8.64
0.631–16.538
4.40
9.04
C18:2
n
-6 (LA)
d
0.267–1.017
4.28
8.48
0.044–1.036
2.83
11.81
C18:3
n
-3 (ALA)
e
0.048–0.121
4.86
7.68
0.02–0.574
4.90
9.53
C20:4
n
-6 (ARA)
f
0.016–0.023
3.61
7.34
0.003–0.089
10.65
33.71
C22:6
n
-3 (DHA)
g
0.008–0.011
5.47
14.64
0.006
8.47
a
Results expressed in grams per 100 g reconstituted product for powder (25 g + 200 g water) and in grams per 100 g for liquid.
b
Results expressed in grams per 100 g product (powder and liquid).
c
MUFAs = Monounsaturated fatty acids.
d
LA = Linoleic acid.
e
ALA = α-Linolenic acid.
f
ARA = Arachidonic acid.
g
DHA = Docosahexaenoic acid.
204