The Role of Ionic Liquid Interaction in the Separation of Fatty Acid Methyl Esters—Polyunsaturated Geometric Isomers in GC–MS

Abstract

Knowledge of the type and level of saturated and unsaturated fatty acids in food and clinical matrices is of practical importance, but the wide variety of fatty acids makes analyses very complex. The discrimination of the geometric isomers of fatty acid needs proper and effective separation conditions. The efficiency of three different stationary phases was evaluated by GC–MS methods in the separation of fatty acids in their methyl ester forms. Significant differences were observed in the efficiencies of polysiloxane-based (non-polar HP-5MS and medium/high polarity DB-225MS) and ionic liquid-based (SLB-IL111) columns. Baseline separation of the geometric isomers of linoleic acid methyl ester was obtained by the extremely polar SLB-IL111 column, showing a preference over the other two columns. The optimization of the experimental conditions (response linearity, limit of detection, limit of quantification, system suitability, intraday and interday repeatability and accuracy) showed the separation power of the ionic liquid interaction in the analyses by using short (25–30 m long) columns. By deducting the general principles of the interaction, predictions can be made for the separation of other isomers. The results facilitate the precise identification of various types of fatty acids in real samples for nutritional information.

Effect of Culture Conditions on Fatty Acid Profiles of Bacteria and Lipopolysaccharides of the Genus Pseudomonas—GC-MS Analysis on Ionic Liquid-Based Column

“…To find the appropriate method for the separations, the method used in our previous work [ 14 ] to separate fatty acid methyl esters with high structural diversity and to test different stationary phase GC columns, served as a basis and was modified and the following settings were found to be suitable. The column temperature was initially held at 50 °C for 0 min, then raised to 220 °C at the rate of 4.5 °C min −1 , held at 220 °C for 1 min, and raised to 260 °C at 50 °C min −1 , held at final temperature for 2 min.…”

“…The fatty acid compositions of bacteria cultured in different media, at different temperatures for short or longer incubation times were investigated by gas chromatography-mass spectrometry (GC-MS) using a separation column with an extremely polar ionic liquid stationary phase. In our previous work the ionic liquid based column compared by other capillary columns with different polarities was found as an accurate and suitable analysis for determination and quantification of FAME components [ 14 ].…”