Novel method for quantification of individual free fatty acids in milk using an in-solution derivatisation approach and gas chromatography-mass spectrometry

An ethyl chloroformate free fatty acid (ECF-FFA) method was developed for quantification of free fatty acids (FFAs) in milk. The method is based on gas chromatography mass spectrometry with ECF in-solution derivatisation and was optimised for the comprehensive analysis of FFAs (C4–C18:3) in bovine milk. Good estimations of all FFAs, including the most water-soluble short chain free fatty acids were achieved by using in-solution derivatisation, which can be ascribed to the fact that an extraction of the milk samples with an organic phase is avoided. FFA standard solutions and raw milk samples were used to validate the proposed method. Correlation coefficients of >0.999 were obtained for all of the standards. Both the repeatability and the within three days stability of the analytical method were high (RSD <4%) for the quantified FFAs in milk. Method recovery of spiked milk samples with three different levels of FFAs was in the range 94–103%.