AOACSPIFANMethods-2017Awards

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G olay & M oulin : J ournal of AOAC I nternational V ol . 99, N o . 1, 2016  219

( 5 ) Performance of the transesterification. —Record the areas of the two internal standard peaks (methyl undecanoate and tritridecanoin) in the analyzed samples. The performance of transesterification (Pt) expressed as a percentage, is calculated on the recovery of the tritridecanoin as a second internal standard as follows:

evaluation, and a list of fatty acids was selected according to the composition (dairy versus nondairy) of analyzed samples and their abundance. Outlier values were removed based on Cochran and/or Grubbs tests following the ISO 5725 guideline. All statistical decisions regarding the evaluation of data were carefully recorded and provided to the ERP to assist in their decision to accord Final Action status in July 2014. Results corresponding to Samples 1–6 were expressed in grams per 100 g finished product, except for Sample 5 (cheese), which are expressed in grams per 100 g extracted fat from cheese. Results corresponding to SPIFAN Samples 7–9 in powder form were expressed in grams per 100 g reconstituted product (25 g powder with 200 g water), and Samples 10–12 were expressed in grams per 100 g liquid products. Results for Samples 7–12 were reported using criteria defined in AOAC SMPR 2012.011. As previously discussed with the ERP during SLV data evaluation, the requirements for repeatability and reproducibility are not fully consistent with the whole range of fatty acids concentration found in the samples. Values were given for fatty acid concentrations of <0.5, ≥0.5 to <3.0, and ≥3.0 g/100 g; however, the quantification limit is (≤0.001) is 500 times lower than the lower fatty acid concentration indicated in SMPR (0.5). The performance requirement at the level of 0.5 cannot be the same for a fatty acid in a concentration at 0.499 in a sample and at 0.001 in another sample (500 times lower). As a consequence, additional limits for repeatability and reproducibility values also need to be fixed in the SMPR for concentrations below 0.5. Proposed repeatability and reproducibility limits are shown in Table 3. The transesterification performance (i.e., recovery between C11:0 FAME and C13:0 TAG) was monitored in all samples and ranged between 98.9 and 100.0% with an RSD value between 0.9 and 1.6%, except for a cheese sample (2.7%). A questionnaire was sent to all participants, along with an invitation to give comments about the performance of the method in their laboratory. Feedback was requested with respect

× × × × 13 m A R S TAG A m c c c c c c ( 11 13 13 11 13

)

Pt

×

=

100

where m c11 is the mass in milligrams of the C11:0 internal standard added to the solution; A c13 internal standard in the chromatogram; R c13 is the response factor of C13:0 relative to C11:0, calculated according to G ( 1 ); S c13 is the stoichiometric factor to convert C13:0 FAME into C13:0 TAG; A c11 is the peak area of the C11:0 internal standard in the chromatogram; and m c13 is the mass in milligrams of the C13:0 internal standard added to the solution. The performance of the transesterification method should be always 100.0±2.0%. When the performance of the transesterification is >102.0 or <98.0%, the origin of the problem could be the following: incomplete transesterification, partial degradation of internal standard(s), or a matrix effect problem. The evaluation of transesterification performance in a blank sample can be used to monitor the stability of reagents and chemicals. is the peak area of the C13:0

Results and Discussion

Forty-six analytes (Table 2) were recorded in 12 selected samples (Table 1) analyzed as double blinds (i.e., 24 analyses) by 18 participants; in total, 19 872 results were collected from the study. The results were carefully evaluated and summarized in an Excel template used for statistical evaluation. Single values reported for one double-blind sample were removed from the

Table 2. Analytes Fatty acid Individual fatty acid  C18:2 n -6

Abrev.

Fatty acids analyzed

LA

C18:2 n -6 C18:3 n -3 C20:4 n -6 C20:5 n -3 C22:6 n -3

 C18:3 n -3  C20:4 n -6  C20:5 n -3  C22:6 n -3

ALA ARA EPA DHA

Group of fatty acid  Saturated fatty acids

SFAs

C4:0, C6:0, C8:0, C10:0, C12:0, C14:0, C15:0, C16:0, C17:0, C18:0, C20:0, C22:0, and C24:0 C14:1 n -5, C15:1 n -5, C16:1 n -7, C17:1 n -7, C18:1 n -9 (and other cis isomers), C20:1 n -9, C22:1 n -9, and C24:1 n -9

 Monounsaturated fatty acids

MUFAs

 Polyunsaturated fatty acids

PUFAs

C18:2 n -6, C18:3 n -6, C18:3 n -3, C20:2 n -6, C20:3 n -3, C20:3 n -6, C20:4 n -6, C20:5 n -3, C22:2 n -6, and C22:6 n -3

Trans fatty acids

TFAs

C18:1 trans , C18:2 trans , and C18:3 trans C18:3 n -3, C20:3 n -3, C20:5 n -3, and C22:6 n -3

 Omega-3  Omega-6  Omega-9

ω-3 ω-6 ω-9

C18:2 n -6, C18:3 n -6, C20:2 n -6, C20:3 n -6, C20:4 n -6, and C22:2 n -6

C18:1 n -9, C20:1 n -9, C22:1 n -9, and C24:1 n -9

Sum of all fatty acids  Total fatty acids

All fatty acids (including CLAs and omega fatty acids)

Transesterification performance

TP

C11:0 and C13:0 (internal standards)