Separation of Structured Lipids by High Performance Liquid Chromatography

Medium-chain triacylglycerols (TAG) [tributyrin (1,2,3-tributyrylglycerol), tricaproin (1,2,3-tricaproylglycerol), and tricaprylin (1,2,3-tricapryloylglycerol)] were subjected to acidolysis with stearic acid or interesterified with hydrogenated soybean oil (HSO) using an immobilized lipase as catalyst for the synthesis of structured lipids (SL.). Normal phase (silica or cyanopropyl phases; NPSIL or NPCN, respectively) and reverse phase (octadecylsilane, RPODS) high performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD) were used to separate the newly synthesized SL. The NP-HPLC methods fully resolved SL-TAG isomers containing butyryl (C4) and long-chain fatty acyl [stearoyl (C18) and palmitoyl (C16)] residues, but SL-TAG isomers composed of caproyl (C6) or capryloyl residues (C8) and long-chain fatty acyl residues were not fully resolved. The latter SL-TAG molecules were resolved using the RP-HPLC method. The HPLC methods were combined with mass spectrometric detection (LC-MS) to characterize the SL molecular species produced.