Direct quantification of fatty acids in human milk by gas chromatography

Human milk provides the key nutrients necessary for the infants’ growth and development. The fatty acid composition of human milk has been extensively studied over the last 20 years and the results obtained by analyzing the fatty acid profile followed by lipid extraction and expressing data as g per 100g of fatty acids. The main drawback is that normalizing data set does not give any information on the amount of fatty acid mother's milk and therefore the level of intake by the infant. The objective of the present study was to develop and validate a direct method to analyze the fatty acid content in liquid human milk samples. Hydrochloric acid in a solution of methanol was selected as the catalyst and methyl undecanoate (11:0) as the internal standard together with tritridecanoin (13:0 TAG) to monitor transesterification performance. The separation of fatty acid methyl esters (FAME) was performed using a 100m highly polar capillary column and a certified calibration mixture used to calculate experimental response factors. The method is suitable to quantify fatty acids in human milk from a 250μL sample and allow expression of the data in mg of fatty acids per deciliter of human milk as well as weight % of fatty acids. The method has been validated and show a good repeatability [CV(r)