Fatty acids patterns in camel, moose, cow and human milk as determined with GC/MS after silver ion solid phase extraction

Silver ion solid phase extraction (Ag+-SPE) followed by GC/EI–MS operated in the selected ion monitoring (SIM) mode was used for the thorough analysis and comparison of fatty acids from bulk milk samples of farmed camel, moose, and cow along with one human milk sample. The GC/EI–MS–SIM mode took advantage of different time windows and enabled the unequivocal assignment of the number of double bonds. GC/MS was also used for structure verification. Ag+-SPE was of particular importance for the separation of cis- and trans-isomers. By the combination of both techniques we were able to determine the amounts of 29 saturated fatty acids (including up to eleven branched-chain fatty acids and the scarcely described 11-cyclohexylundecanoic acid which was detected in all samples), 16 cis- and 23 trans-monoenoic fatty acids as well as 19 polyunsaturated fatty acids including the conjugated linoleic acid (CLA) 18:2(9,11tr). Characteristic differences were observed in that human milk differed from the animal milks by its lower trans-fatty acid and branched-chain fatty acid content. In this set of samples, the branched-chain fatty acid content was highest in camel milk while moose milk contained the highest proportion of 18:1(9), 18:3(9,12,15), and 22:6(4,7,10,13,16,19). Although only one bulk sample was available for the animal milk the amounts determined fitted well with published data. Thus, this approach might be helpful to establish a more comprehensive data base for statistic evaluation.