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

Abstract

This article reviews papers published over the period 1989-94 concerning applications of cyclodextrin derivatives (CDDs) to the separation of volatile racemates in the essential oil, extract, flavour and aroma fields by CGC techniques. For each application, the racemate separated, the CDD used for the separation and the matrix analysed are reported. The applications are grouped by the analytical technique employed: capillary gas chromatography and capillary gas chromatography-mass spectrometry (CGC and CGC-MS); multidimensional gas chromatography (MDGC); capillary gas chromatography-isotope ratio-mass spectrometry (CGC-IRMS); liquid chromatography-capillary gas chromatography (HPLC-CGC).KEY WORDS cyclodextrin derivatives; capillary gas chromatography; (CGC); CGC-MS; MDGC;CGC-IRMS; HPLC-CGC; enantiomer separation; essential oils; extracts; flavour; aroma INTRODUCTIONThe introduction of derivatized cyclodextrins (CDD) as stationary phases to separate volatiles has been a milestone in GC enantiomer separation. The development of CDDs has greatly facilitated these separations, most of which are now carried out without derivatization. Since the number of racemates separated by CDDs is now very large, and since the stability and reproducibility of capillary GC columns prepared with CDDs is now very high, the use of CDDs is becoming increasingly widespread in routine analysis. Enantiomer separation is fundamental in the fields of flavours and essential oils, because it gives access to biogenetic information concerning a compound and very often, as a consequence, the corresponding matrix; it makes it possible to determine the enantiomeric excess of a component in a sample very quickly, and last, but not least, to identify possible adulterations in products of natural origin.A number of interesting reviews on different aspects of these fields have already been published. In particular, Mosand1122 reviewed the This article reviews papers concerning applications of CDD to the separation of volatile racemates in the essential oil and flavour fields by CGC techniques. We will therefore not deal with theory, separation mechanisms, chromatographic behaviour, development of new CDDs for CGC or packed column GC separation.The article is divided into sections, by the analytical technique employed: capillary gas chromatography and capillary gas chromatography-mass spectrometry (CGC and CGC-MS); multidimensional gas chromatography (MDGC); capillary gas chromatography-isotope ratio-mass spectrometry (CGC-IRMS), liquid chromatography-capillary gas chromatography (LC-CGC). Each section is in turn divided into two subsections, the first dedicated to essential oils and the second to extracts and flavour and aroma compounds: thus, the analysis of the same compound, either in the same or in different matrices, if carried out with different techniques, The period covered is 1989-94; articles reported in Chemical Abstracts and/or the bibliography section of the Journal of Chromatography and Analytical Abstracts are reviewed. Considering the...

The Effect of Processing on the Chiral Aroma Compounds in Cherries (Prunus avium L.)

“…For example, (/£)-(+)-limonene has an orange-like aroma while («S)-(-)-limonene is turpentine-like; (£)-(+)-carvone is characteristic of caraway while its enantiomer has a spearmint odor (2). However, other chiral compounds, such as y and 6-lactones, show very little enantioselectivity of odor perception (7). The occurrence of chiral flavor compounds in enantiomeric excess provides the analyst with a means of authenticating natural flavorings, essential oils, and other plant extracts.…”

“…Chiral odor compounds may show qualitative and quantitative differences in their odor properties (7). For example, (/£)-(+)-limonene has an orange-like aroma while («S)-(-)-limonene is turpentine-like; (£)-(+)-carvone is characteristic of caraway while its enantiomer has a spearmint odor (2).…”

Essential oils and volatiles: sample preparation and analysis. A review.

“…[53] Since then, several hundreds of articles have been published dealing with the theory of ES-GC recognition with CDs, synthesis of new CD derivatives, their enantioselectivity and applications; many of these concern the flavour and fragrance field. [54][55][56][57] A universal CD derivative suitable to provide the separation of most significant racemates in this field has not yet been found, mainly because of the intrinsic mechanism of chiral recognition in GC, which is based on a host-guest interaction of each enantiomer of a racemate with the CD selector, the separation depending on the rather small difference in the energy of interaction of each enantiomer with the CD chiral selector. [58,59] A laboratory must therefore have available at least two columns coated with different CD derivatives to enable separation of at least 80% of the most common racemates in the flavour and fragrance field.…”

Gas Chromatographic Analysis of Plant and Insect Surface Compounds: Cuticular Waxes and Terpenoids

“…The main reasons for this are the wider range of operating temperatures, the inertness and efficiency of columns prepared by high temperature silylation, the possibilities of tuning column polarity by using different diluting phases, the small amounts of CD necessary to prepare columns, the shorter analysis times, and the possibility of measuring the thermodynamic parameters involved in enantiomer discrimination. Papers published over the period 1989-94 concerning applications of cyclodextrin derivatives (CDDs) to the GC separation of volatile racemates in the essential oil, extract, flavour and aroma fields were reviewed by Bicchi et al (1995).…”