Abnormal composition of commerical waxes revealed by supercritical fluid chromatography

Glycolipid class profiling by packed-column subcritical fluid chromatography

The potential of packed-column subcritical fluid chromatography (SubFC) for the separation of lipid classes has been assessed in this study. Three polar stationary phases were checked: silica, diol, and poly(vinyl alcohol). Carbon dioxide (CO2) with methanol as modifier was used as mobile phase and detection performed by evaporative light scattering detection. The influence of methanol content, temperature, and pressure on the chromatographic behavior of sphingolipids and glycolipids were investigated. A complete separation of lipid classes from a crude wheat lipid extract was achieved using a modifier gradient from 10 to 40% methanol in carbon dioxide. Solute selectivity was improved using coupled silica and diol columns in series. Because the variation of eluotropic strength depending on the fluid density changes, a normalized separation factor product (NSP) was used to select the nature, the number and the order of the columns to reach the optimum glycolipid separation.

Quality assurance of commercial beeswax II. Gas chromatography-electron impact ionization mass spectrometry of alcohols and acids

Gas chromatography with mass spectrometric detection was used to find the fraction of alcohols and acids present in pure beeswax from Apis mellifera. Some new compounds not described till now were found, such as a family of unsaturated linear fatty acids, several hydroxyacids and 1,2,3-propanetriol monoesters. The chromatographic profiles obtained from pure beeswax and bee-rejected foundation beeswax can be used to discriminate them; they mainly differ in the amount of some acids and alcohols.

Retention behaviour of ceramides in sub-critical fluid chromatography in comparison with non-aqueous reversed-phase liquid chromatography

This study was devoted to the development of an analytical method for ceramide analysis in packed subcritical fluid chromatography (pSubFC). Monofunctional grafted silica support was found to be more suitable for ceramide analysis. Five Kromasil columns were coupled and the parameters, temperature, pressure and percentage of organic modifier in CO2 were optimised, considering selectivity and analysis time. The final conditions were 31 degrees C, 6% of methanol (MeOH) and 13 MPa. In these conditions the selectivity for structural differences (methylene group, unsaturation or two different bases) were studied. As classically observed, the methylene selectivity decreased with the increase of the eluotropic strength. Moreover, unlike in non-aqueous reversed-phase liquid chromatography (NARP-LC), adding a further unsaturation and two further methylene groups on ceramide results to an increase of retention in pSubFC. Moreover, this last technique allowed to separate ceramides with the same total number of carbons containing unsaturated fatty acids, when the distribution of carbon number of the two chain is very different. These results had enabled to plot retention chart in order to predict ceramide structure in view to identify additional ceramide. This retention chart was finally compared with the one already obtained in NARP-LC.