Precision of low trans fatty acid level determination in refined oils. Results of a collaborative capillary gas-liquid chromatography study

The results of a collaborative study by 38 laboratories were analyzed statistically to calculate the precision of a novel capillary gas‐liquid chromatography (GLC) method for the determination of low levels of trans fatty acids (TFA) in edible oils. The participants came from 17 countries, mainly European, and were spread evenly between Unilever companies and external laboratories. All participants used the same GLC method, including a temperature optimization step, which is suitable for the determination of a large range of TFA levels in refined oils and fats and for the determination of total saturated fatty acid, cis mono‐ and cis‐cis methylene‐interrupted polyunsaturated fatty acid isomers. For TFA levels down to 0.5%, the collaborative study yielded values for Rwithin that ranged from 0.08 to 0.13% (absolute values) and for Rbetween from 0.2 to 0.4%, depending on the isomer distribution in a particular edible oil. The proposed GLC method allows reliable TFA analysis at low levels that is suitable for monitoring oil processing practices and intake control.