Instability of hexane–acetonitrile mobile phases used for the chromatographic analysis of triacylglycerides

Abstract

Comprehensive 2-D LC is an emerging separation technique that has seen a rapid increase in applications in the last decade. The technique has been applied for the separation of numerous complex mixtures including triacylglycerides (TAG). Determination of TAG in food products such as rice, palm, and canola oils have been previously described and the technique of choice utilizes a silver-modified silica column with hexane-ACN as the mobile phase. Repeated retention time inconsistencies were experienced in our studies when this mobile phase was applied to the separation of natural and synthetic mixtures containing TAG. The present report summarizes a study performed to determine the relative stability of ACN, propionitrile (PCN), and butyronitrile (BCN) at concentrations ranging from 0.43 to 2.8% in hexane and heptane. The data obtained suggest that unless evaporative loss of the mobile phase is prevented, TAG retention time irreproducibility can be significant when using mobile-phase mixtures prepared with ACN or PCN. BCN should be used as the solvent modifier in cases where evaporation cannot be prevented.

Comprehensive two‐dimensional liquid chromatography with evaporative light‐scattering detection for the analysis of triacylglycerols in Borago officinalis

“…Although ACN has a polarity greater than BCN, the latter, in mixture with Hex, does not show miscibility issues and it degrades more slowly. As a result, the combination of the two solvents for the D1 mobile phase showed greater repeatability in terms of retention times and shorter analysis times than Hex/ACN because a higher amount of BCN could be used 29. On the other hand, when developing an Ag + ‐LC×RP‐LC system, the mobile phase used in the D1 is always stronger than that used in the D2, and therefore distorted and multiple peaks can be obtained 30.…”

Advances in Silver Ion Chromatography for the Analysis of Fatty Acids and Triacylglycerols—2001 to 2011

“…As an alternative, 2% acetic acid in hexane was used for the resolution of CLA ME, 34 and 0.15% acetonitrile in 2-octane was found to be appropriate for the fractionation of trans and cis monoenoic ME. 35 Propionitrile and butyronitrile were also tested as modifiers for both CLA 36,37 and TAG 38 separations. Heptane-acetonitrile and heptaneacetone were successfully applied to the separation of positionally isomeric TAG and TAG containing oleoyl-and elaidyl-moieties in partially hydrogenated vegetable oils.…”

Multidimensional Liquid Chromatography Coupled with Tandem Mass Spectrometry for Identification of Bioactive Fatty Acyl Derivatives

“…In general, elution order of analytes by this technique is saturated, trans-unsaturated, mono-unsaturated, and so on. A number of experimental parameters and analyte variables have been explored in relation to retention factor allowing implementation of this methodology in a predictable manner (Christie, 1998b; Shan and Wilson, 2002; Harfmann et al, 2008). One exception to typical chromatographic separations is that retention of analytes in silver ion chromatography is reduced at lower temperature (Adlof and List, 2004).…”