IUPAC gas chromatographic method for determination of fatty acid composition: collaborative study

Area of Science:

• Analytical Chemistry
• Food Chemistry
• Organic Chemistry

Background:

• Standardized methods are crucial for accurate fatty acid analysis in diverse matrices.
• Gas-liquid chromatography (GLC) is a key technique for separating and quantifying fatty acid methyl esters.
• Previous methodologies required validation for broad applicability, including milk fats.

Purpose of the Study:

• To collaboratively study and validate International Union of Pure and Applied Chemistry (IUPAC) methods II.D.19 and II.D.25 for fatty acid methyl ester preparation and GLC analysis.
• To assess the applicability of these IUPAC methods across various sources, including animal fats, vegetable oils, fish oils, and specifically milk fat.
• To evaluate the intra- and interlaboratory variation and reproducibility of the proposed methods.

Main Methods:

• International collaborative study involving 23 laboratories.
• Preparation and gas-liquid chromatography (GLC) analysis of fatty acid methyl esters.
• Analysis of known mixtures, vegetable oils, fish oil, and butterfats, including blind duplicates.

Main Results:

• Satisfactory reproducibility and accuracy were achieved for higher fatty acids (14:0-22:1) in vegetable and fish oils.
• Results for higher fatty acids were consistent with an American Oil Chemists' Society (AOCS) check sample program.
• Poor recoveries and reproducibility were observed for butyric acid analysis in butterfat, with a coefficient of variation around 19%.

Conclusions:

• The IUPAC methodology for GLC analysis of fats and oils, excluding milk fats, is reliable and has been adopted by AOAC.
• The method requires further refinement for accurate butyric acid quantification in milk fat.
• The collaborative study successfully identified strengths and limitations of the IUPAC methods for fatty acid analysis.