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1612447 
Journal Article 
Two methods for the separation of monounsaturated octadecenoic acid isomers 
Villegas, C; Zhao, Y; Curtis, JM 
2010 
Yes 
Journal of Chromatography A
ISSN: 0021-9673
EISSN: 1873-3778 
1217 
5 
775-784 
English 
20022011 
WOS:000274351600022 
The identification and quantification of complex mixtures of cis and trans octadecenoic (18:1) fatty acid isomers presents a major challenge for conventional one-dimensional GC/FID analysis of their methyl esters. We have compared the use of two methods to achieve optimized separations of positional and geometrical octadecenoic fatty acid isomers-comprehensive two-dimensional gas chromatography (GCxGC), and silver ion high performance liquid chromatography interfaced to atmospheric pressure photoionization (APPI) mass spectrometry. Nine isomers of octadecenoic acid methyl ester were well separated on a single silver ion column with a mobile phase of 0.018% acetonitrile and 0.18% isopropanol in hexane. Reproducible retention times were obtained with relative standard deviations of around 1% over 5 injections. The extra selectivity and reproducibility afforded by APPI-MS, together with the wide separation of cis and trans isomers by silver ion chromatography, resulted in a promising method for measurement of octadecenoic acid FAME. The GCxGC separation was performed using various column combinations, and optimal separation was obtained by coupling an ionic liquid column (Supelco SLB-IL100 [1,9-di(3-vinyl-imidazolium) nonane bis(trifluoromethyl) sulfonyl imidate]) in the first dimension with a SGE BPX50 (50% phenyl polysilphenylene-siloxane) in the second dimension. These methods have been applied to the analysis of octadecenoic acid in milk and beef fat. 
Comprehensive two-dimensional gas chromatography; GC x GC; C18:1 isomers; Milk fat; Beef fat; Ag+-HPLC/APPI-MS