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Title: ANALYSIS OF TRIGLYCERIDE ISOMERS BY SILVER-ION HPLC: EFFECT OF COLUMN TEMPERATURE ON RETENTION TIMES

Author
item Adlof, Richard
item List, Gary

Submitted to: Journal of Chromatography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/2004
Publication Date: 3/16/2004
Citation: Adlof, R.O., List, G.R. 2004. Analysis of triglyceride isomers by silver-ion hplc: effect of column temperature on retention times. Journal of Chromatography. 1046:109-113.

Interpretive Summary: Silver ion high performance liquid chromatography (Ag-HPLC) has shown itself to be a useful technique for analyzing a variety of fats and oils. The authors demonstrated, for the first time, that using but a single solvent and a chiller/heater to control column temperatures, triglycerides actually eluted more rapidly at lower column temperatures. This effect is just the opposite to that observed in gas chromatography, but could be utilized to develop a single-solvent, temperature-programmed Ag-HPLC system which, like gas chromatography, could be used to rapidly analyze a wide range of samples, with the improved reproducibility and sample separation(s) required for the development of standard methods.

Technical Abstract: Ag-HPLC, utilizing columns packed with silver ions bonded to a silica or similar substrates, has proven to be a tremendously powerful technique for the analytical separation of cis and trans geometric and positional fatty acid methyl ester (FAME) and triacylglycerol (TAG) isomers (see Ref. 1-5 for reviews). In this manuscript we utilized a HPLC column chiller/heater to study the effects column temperature on retention of TAG isomers in silver ion chromatography (Ag-HPLC). Varian-ChromPack ChromSpher Lipids columns and an isocratic solvent system of 1.0% acetonitrile (ACN) in hexane were utilized. TAG retentions were found to decrease with decreasing temperature, a result just the opposite to temperature effects noted in gas chromatography. A possible explanation may be a temperature-induced change in the partition coefficient between ACN and hexane. In GC, a more-rapid exchange between the solute and the liquid stationary phase in the GC column has been used to explain the more rapid elution of FAMEs with increasing temperatures. In Ag-HPLC, the ACN competes with double bond electrons of the eluting sample with the silver ions. At lower temperatures, the ACN is less soluble in the hexane, and therefore more ACN is available for this competition, a situation analogous to a higher percentage of ACN in the eluting solvent.