2018 - Ionic liquid phases with comprehensive two-dimensional gas chromatography of fatty acid methyl esters
New generation inert ionic liquid (iIL) GC columns IL60i, IL76i and IL111i, comprising phosphonium or imidazolium cationic
species, were investigated for separation of fatty acid methyl esters (FAME). In general, the iIL phases provide comparable
retention times to their corresponding conventional columns, with only minor selectivity differences. The average tailing factors
and peak widths were noticeably improved (reduced) for IL60i and IL76i, while they were slightly improved for IL111i. Inert IL
phase columns were coupled with conventional IL columns in comprehensive two-dimensional GC (GC × GC) with a solid-state
modulator which offers variable modulation temperature (TM), programmable TM during analysis and trapping stationary phase
material during the trap/release (modulation) process, independent of oven T and column sets. Although IL phases are classified
as polar, relative polarity of the two phases comprising individual GC × GC column sets permits combination of less-polar IL/
polar IL and polar IL/less-polar IL column sets; it was observed that a polar/less-polar column set provided better separation of
FAME. A higher first dimension (1D) phase polarity combined with a lower 2D phase polarity, for instance 1D IL111i with 2D
IL59 gave the best result; the greater difference in 1D/2D phase polarity results in increasing occupancy of peak area in the 2D
space. The IL111i/IL59 column set was selected for analysis of fatty acids in fat and oil products (butter, margarine, fish oil and
canola oil). Compared with the conventional IL111, IL111i showed reduced column bleed which makes this more suited to GC ×
GC analysis of FAME. The proposed method offers a fast profiling approach with good repeatability of analysis of FAME.
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