Commission Regulation (EEC) No 2568/91 of 11 July 1991 on the characteristics of olive oil and olive-residue oil and on the relevant methods of analysis (c. 2568)

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[F1 ANNEX X U.K. DETERMINATION OF FATTY ACID METHYL ESTERS BY GAS CHROMATOGRAPHY

Textual Amendments

F1 Substituted by Commission Implementing Regulation (EU) 2015/1833 of 12 October 2015 amending Regulation (EEC) No 2568/91 on the characteristics of olive oil and olive-residue oil and on the relevant methods of analysis.

PART B U.K. ANALYSIS OF FATTY ACID METHYL ESTERS BY GAS CHROMATOGRAPHY

5. EXPRESSION OF RESULTS U.K.

5.1. Qualitative analysis U.K.

Identify the methyl ester peaks of the sample from the chromatogram in Appendix B, figure 1, if necessary by interpolation, or by comparison with those of the methyl esters reference mixtures (as indicated at point 2.3).

5.2. Quantitative analysis U.K.

5.2.1. Determination of the composition U.K.

Calculate the mass fraction w _i of the individual fatty acid methyl esters, expressed as a percentage by mass of methyl esters, as follows:

5.2.2. Method of calculation U.K.

5.2.2.1. General case U.K.

Calculate the content of a given component i, expressed as a percentage by mass of methyl esters, by determining the percentage represented by the area of the corresponding peak relative to the sum of the areas of all the peaks, using the following formula:

w _i = (A _i /ΣA) × 100

where:

• A _i is the area under the peak of the individual fatty acid methyl ester i ;

• ΣA is the sum of the areas under all the peaks of all the individual fatty acid methyl esters.

The results are expressed to two decimal places.

Note 4: For fats and oils, the mass fraction of the fatty acid methyl esters is equal to the mass fraction of the triacylglycerols in grams per 100 g. For cases in which this assumption is not allowed, see 5.2.2.2. U.K.

5.2.2.2. Use of correction factors U.K.

In certain cases, for example in the presence of fatty acids with less than eight carbon atoms or of acids with secondary groups, the areas shall be corrected with specific correction factors (Fci). These factors shall be determined for each single instrument. For this purpose suitable reference materials with certified fatty acid composition in the corresponding range shall be used.

Note 5: These correction factors are not identical to the theoretical FID correction factors, which are given in Appendix A, as they also include the performance of the injection system etc. However, in the case of bigger differences, the whole system should be checked for performance. U.K.

For this reference mixture, the mass percentage of the FAME i is given by the formula:

w _i = (m _i /Σ m) × 100

where

• m _i is the mass of the FAME i in the reference mixture;

• Σm is the total of the masses of the various components as FAMEs of the reference mixture.

From the chromatogram of the reference mixture, calculate the percentage by area for the FAME i as follows:

w _i = (A _i /ΣA) × 100

where:

• A _i is the area of the FAME i in the reference mixture;

• ΣA is the sum of all the areas of all the FAMEs of the reference mixture.

The correction factor F _c is then

F _c = (m _i × ΣA)/(A _i /Σm)

For the sample, the percentage by mass of each FAME i is:

w _i = (F _i × A _i )/Σ (F _i × A _i )

The results are expressed to two decimal places.

Note 6: The calculated value corresponds to the percentage of mass of the individual fatty acid calculated as triacylglycerols per 100 g fat. U.K.

5.2.2.3. Use of an internal standard U.K.

In certain analyses (for example where not all of the fatty acids are quantified, such as when acids with four and six carbons are present alongside acids with 16 and 18 carbons, or when it is necessary to determine the absolute amount of a fatty acid in a sample) it is necessary to use an Internal Standard. Fatty acids with 5, 15 or 17 carbons are frequently used. The correction factor (if any) for the Internal Standard should be determined.

The percentage by mass of component i, expressed as methyl esters, is then given by the formula:

w _{i =} (m _IS × F _i × A _i )/(m × F _IS × A _IS )

where:

• A _i is the area the FAME i ;

• A _IS is the area of the internal standard;

• F _i is the correction factor of the fatty acid i , expressed as FAME;

• F _IS is the correction factor of the internal standard;

• m is the mass of the test portion, in milligrams

• m _IS is the mass of the internal standard, in milligrams.

The results are expressed to two decimal places.]