Assessment of ionic liquid stationary phases for the GC analysis of fatty acid methyl esters

Abstract

The gas chromatographic separation of fatty acid methyl esters (FAMEs) on ionic liquid stationary phases was investigated. Seven commercially available ionic liquid columns were tested using a test mixture containing 37 fatty acid methyl esters. The influence of column temperature on the elution order was studied using five different temperature programs. Retention times were highly reproducible. Similar retention behavior was observed for the IL59, IL60, and IL61 columns. The peak pair C18:1 cis/trans was not baseline resolved on these columns, whose stationary phases are highly similar. C18:2 cis/trans, C18:3 n6/n3, and C20:3 n6/n3 were baseline separated on all columns. Baseline separation of the complete test mix was only obtained on the IL82 column using a heating rate of 5 K/min. In general, retention times decreased with increasing column polarity but unsaturated FAMEs were retained stronger compared to their saturated counterparts. Except for the IL59 column, retention crossover was observed when the temperature program was changed.

Gas chromatographic analysis of fatty acid methyl esters of milk fat by an ionic liquid derived from L-phenylalanine as the stationary phase

“…Saturated FAMEs elute after the unsaturated FAMEs in the 20-m AAIL column. In contrast, in the PEG column and in other ILbased commercial columns such as SLB-IL59, SLB-IL60 and SLB-IL100 [25], with slightly higher a-term [38] compared to the AAIL column, the saturated FAMEs elute before the unsaturated FAMEs. Moreover, using the C2 column, the cis-FAME isomers elute before the trans-FAME isomers, and the retention time of the FAMEs increases as the unsaturation is closer to the end of the chain.…”

“…In this context, novel stationary phases comprising ionic liquid compounds have been introduced for the separation of FAMEs [21][22][23][24][25].…”

Chromatographic efficiency of polar capillary columns applied for the analysis of fatty acid methyl esters by gas chromatography

“…The four columns applied in the study were two of medium polarity, BP20 (SGE, Ringwood, Australia) and DB23 (Agilent, Santa Clara, CA, USA), one of high polarity, BPX70 (SGE), and an ionic liquid column of very high polarity, SLB‐IL100 (Supelco, Bellefonte, PA, USA). The columns had the following stationary phase structures: PEG (BP20), 50% cyanopropyl‐methyl‐polysiloxane (DB23), 70% cyanopropyl‐polysilphenylene‐siloxane (BPX70) and 1,9‐di(3‐vinylimidazolium)nonane bis(trifluoromethylsulfonyl)imide (SLB‐IL100) . All columns were 30 m long with nominal internal diameter from 0.22 to 0.25 mm and nominal film thickness from 0.20 to 0.25 μm.…”

Occurrence of oleic and 18:1 methyl-branched acyl chains in lipids of Rhodobacter sphaeroides 2.4.1

“…Recently, the introduction of GC columns with highly polar stationary phases, specifically ionic liquids (ILs), has further improved the separation of closely-related FAMEs [36][37][38]. Such a column-type (see "Experimental") was employed in the present work to separate positional and geometric FA isomers.…”