High temperature multidimensional gas chromatographic approach for improved separation of triacylglycerols in olive oil

Heart-cut multidimensional gas chromatographic (H/C MDGC) methods under suitable flow and high temperature (T) program conditions were developed to separate olive oil triacylglycerols (TAGs). Different column sets were selected for further evaluation, each with relatively short non-polar first dimension (1D) and mid-polar second dimension (2D) columns of high T limits (350 °C). The 1D separation displayed three major groups of peaks in an area ratio of approximately 5:33:62 (of increasing retention), using flame ionisation detection (FID). Four groups of minor peaks, with 2 of them located between the major peaks, were also detected. The H/C fractions of the minor peaks, and sub-sampled regions across the major peaks eluting from the 1D outlet, were cryotrapped at the 2D inlet. The trapped TAGs then underwent temperature programmed 2D separation. Each of the 'H/C' zones generally gave 2-5 - and in some cases more - separated peaks of TAGs on the 2D column, under suitable flow condition and phase polarity that resulted in improved separation. Six sub-sampled H/Cs from various regions of the individual peaks from the 1D column were simultaneously trapped and released to 2D, resulting in apparently more than 22 individual TAG peaks. According to their different retention times, different TAGs were revealed within each of the 3 major groups, using H/C sub-sampling. A comprehensive sampling strategy that covers most of the 1D peaks further revealed the presence of more TAGs in the olive oil sample. This tandem column strategy was able to resolve more components than that usually observed on a single column.