Analysis of north atlantic and baltic fish oil triacylglycerols by high‐performance liquid chromatography with a silver ion column

Abstract

AbstractTriacylglycerols from Atlantic herring (Clupea harengus), sandeel (Ammodytes sp.) and Baltic herring (Clupea harengus membras) have been fractionated by silver ion high‐performance liquid chromatography. An ion exchange column loaded with silver ions was the stationary phase, and a gradient in the mobile phase from 1,2‐dichloroethane/dichloromethane (1∶1, v/v) to acetone and then to acetone/acetonitrile (2∶1, v/v) was used to effect the separation with light‐scattering (i.e., mass) detection. Fractions were collected via a streamsplitter, and fatty acid methyl esters were prepared by transesterification in the presence of an internal standard for identification and quantification by gas liquid chromatography. Triacylglycerols were separated according to the number of double bonds in the fatty acyl residues. Resolution was excellent at first, when the least unsaturated molecules eluted (trisaturated to dimonoene‐monodiene fractions). Base‐line resolution could no longer be achieved when molecules containing trienoic or more highly‐unsaturated fatty acids began to elute because of overlapping components. Nonetheless, some valuable separations of species containing two saturated and/or monoenoic fatty acids and one polyenoic fatty acid were achieved. Double bond indices (average number of double bonds in each triacylglycerol molecule) were calculated to estimate the separations possible. Fractions containing at least 11–14 double bonds per molecule were obtained.