Quantification of Fatty Acid Methyl Esters in Various Biological Matrices by LC-DAD and LC-MS after One-Step Transesterification

Abstract

The investigation of lipids is a complex field and many analytical methods are applied. Gas chromatography (GC) methods are the standard methods; however, GC systems are not available for every researcher. Hence, an alternative liquid chromatography (LC) method was designed. The LC method was developed and validated for separation of C16:n and C18:n fatty acid methyl esters (FAMEs). Baseline-separation of eight FAMEs was achieved with one C18 column. Two ways of detection (diode array detector, DAD, and mass spectrometry, MS), were established and compared. The validation results proved that the method is precise (RSD 0.99) for all analysed FAMEs. Limits of detection (LOD) down to 3 ng and limits of quantification (LOQ) down to 6 ng were achieved. For sample preparation, a one-step transesterification method was used. In bacon fat, duckling lard, and butter, palmitic acid, stearic acid, and oleic acid were the main fatty acids. Olive oil had the highest oleic acid content (60% w/w). Linseed extract showed the highest linolenic acid content (60% w/w). In fungi extract, only a few fatty acids were detected. The highest fatty acid diversity was found in algae extract. Seven of the eight investigated fatty acids were found therein including C16 polyunsaturated fatty acids (PUFAs); further, uncommon C16 and C18 PUFAs were identified. In conclusion, the LC method with DAD detection represents a simple alternative to the usually used GC methods. Using MS detection, unknown compounds can be additionally identified and 10-fold lower LODs can be achieved.