Gas chromatographic separation of the fatty acid methyl esters prepared from dairy products, partially hydrogenated oils, and refined vegetable oils applying a negative temperature gradient

Abstract

AbstractTo date no single gas chromatographic method can simultaneously measure all fatty acids (FA), including trans‐FA (TFA), that are contained in dairy products, partially hydrogenated oils (PHO), and refined vegetable oils. Using 100% poly(biscyanopropyl siloxane) capillary columns, ruminant and dairy fats are preferentially analyzed by applying temperature programs that separate short chain FA, but not trans‐18:3 from 20:1. Refined vegetable oils and PHO are preferentially analyzed by applying isothermal elutions that provide quantification of all 18 carbon TFA including trans‐18:3 FA, but not of all short chain FA. In this short communication, we propose a temperature program method capable of simultaneously measuring short chain FA and all 18 carbon TFA including trans‐18:3 by applying a negative temperature gradient after the elution of trans‐18:1. A simplified version of the method is also described for equipment not able to perform negative temperature gradients.