Cyclodextrin derivatives in GC separation of enantiomers of essential oil, aroma and flavour compounds

Gas chromatography of essential oil: State-of-the-art, recent advances, and perspectives

This review is an overview of the recent advances of gas chromatography in essential oil analysis; in particular, it focuses on both the new stationary phases and the advanced analytical methods and instrumentations. A paragraph is dedicated to ionic liquids as gas chromatography stationary phases, showing that, thanks to their peculiar selectivity, they can offer a complementary contribution to conventional stationary phases for the analysis of complex essential oils and the separation of critical pairs of components. Strategies to speed-up the analysis time, thus answering to the ever increasing request for routine essential oils quality control, are also discussed. Last but not least, a paragraph is dedicated to recent developments in column miniaturization in particular that based on microelectromechanical-system technology in a perspective of developing micro-gas chromatographic systems to optimize the energy consumption as well as the instrumentation dimensions. A number of applications in the essential oil field is also included.

Complexes of peracetylated cyclodextrin in a non-aqueous aprotic medium: the role of residual water

Not all peracetylated cyclodextrins can be completely dried and water protons can be invisible due to the overlapping signals of the acetyl groups. Apparent stability constants of complexes were also calculated.

Peralkylated-β-cyclodextrin used as gas chromatographic stationary phase prepared by sol–gel technology for capillary column

For the first time, three peralkylated-beta-cyclodextrins (beta-CD), permethylated-beta-CD, perethylated-beta-CD and perpentylated-beta-CD, were coated onto the fused-silica capillary by sol-gel method with simplicity and rapidity. Multiple steps in conventional column preparation technology were avoided. Also, these new columns demonstrated many inherent advantages, the main being the outstanding thermal stability (up to 300 degrees C), high number of theoretical plates, excellent column-to-column and run-to-run reproducibility, and pronounced selectivity for positional isomers and enantiomers. Using n-tridecane as a test reagent (k = 4.18), an efficiency value of 3520 theoretical plates/m was obtained on a sol-gel perpentylated-beta-CD capillary column (15 m x 0.25 mm I.D.). On the basis of the results, we proposed that the peralkylated-beta-CD, which has no terminal hydroxyl group, is encapsulated in the sol-gel network and the whole matrix is chemically bonded to the surface of the fused-silica tubing.

Consequences of variable purity of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin determined by liquid chromatography-mass spectrometry on the enantioselective separation of polychlorinated compounds

The composition of 10 batches of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (PM-CD) from different suppliers was determined by high-performance liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometry (MS). Considerable differences were found. Some batches consisted of more than 95% pure PM-CD, whereas others were not completely derivatised or contained a significant amount of by-products. Some suggestions about the structures of these impurities are given though neither nuclear magnetic resonance spectroscopy nor MS-MS investigations could completely reveal their nature. Capillaries for high-resolution gas chromatography were coated with the batches of most differing composition. They demonstrated widely varying column performance and separation properties for selected chiral polychlorinated substances such as chlordane compounds, o,p'-DDT, o,p'-DDD, alpha-hexachlorocyclohexane and atropisomeric polychlorinated biphenyls. The best enantioselectivity was obtained with the purest PM-CD. Compared to separations reported in the literature, a broader enantioselectivity was observed and also trans-heptachlor epoxide and oxychlordane could be resolved into enantiomers.

Cyclodextrin derivatives as chiral selectors for direct gas chromatographic separation of enantiomers in the essential oil, aroma and flavour fields

This article reviews papers published over the period 1995-1998 dealing with the application of cyclodextrin derivatives (CDs) as chiral selector for direct enantiomer GC separation of volatile optically active components in the essential oil, extract, flavour and aroma fields. For each application, the racemate analysed, the CD employed as chiral selector and the matrix investigated are reported. The applications are grouped by analytical technique employed: capillary gas chromatography and capillary gas chromatography-mass spectrometry (GC and GC-MS); two-dimensional gas chromatography (GC x GC); capillary gas chromatography-isotope ratio-mass spectrometry (GC-IRMS); liquid chromatography-capillary gas chromatography (LC-GC).