Enantio-MDGC

E. Podehrad, M. Heil, S. Leih, B. Geier, T. Beck, A. Mosandl, A. C. Sewell and H. Bohles, Analytical approach in diagnosis of inherited metabolic diseases maple syrup urine disease (MSUD)-simultaneous analysis of metabolites in urine by enantioselective multidimensional capillary gas chromatography-mass specti ometiy (enantio-MDGC-MS) , 7. High Resolut. Chromatogr. 20 355-362(1997). 

Kreck, M., Scharrer, A., Bilke, S., Mosandl, A. (2002) Enantioselective analysis of monoter-pene compounds in essential oils by stir bar sorptive extraction (SBSE)-enantio-MDGC-MS. Flavour Fragrance ]. 17 32-40. 

Fig. 17.3 Enantioselective multidimensional gas chromatography (enantio-MDGC), Live-T column switching, Siemens Sichromat [52]...

The combination of enantio-MDGC with high-resolution MS or mass-selective detectors, both used in full scan or (at least) in the multiple ion monitoring (MIM) mode is currently the most potent analytical tool in enantioselective analysis of chiral compounds from complex mixtures. 

In the flavour extract of apricots, racemic dihydroactinidiolide (DHA) was found as the first natural racemate detected by enantio-MDGC analysis [16]. The absolute configurations and the optical activities have been reported to be (R)-(-) and (S)- +) enantiomers, respectively [17, 18]. 

Fig. 17.5 Enantioselective analysis of germacrene D from the essential oil of different Solidago canadensis plants, using the enantio-MDGC-mass spectrometry (MS) technique [21]...

The simultaneous stereoanalysis of y-lactones and d-lactones using enantio-MDGC has been reported (Fig. 17.7). This technique was applied to many fruits proving that enantiomeric ratios of y-lactones and d-lactones can be used as indicators of authenticity, as the genuine enantiomeric purities remain unaffected during fermentation and all other stages of fruit processing [27]. 

Fig. 17.7 Simultaneous stereoanalysis of y-lactones and 5-lactones using enantio-MDGC (main column chromatogram of references ). Elution order y-lactones 4R (I), 4S (II) 5-lactones 5-Ce, S-Cr. 5R (I), 5S (II) S-Cs-S-Cu. 5S (I), 5R (II) [27]...

Fig. 17.10 Stir-bar sorptive extraction-enantio-MDGC-MS analysis of tea tree oil, main column separation [45]...

Enantio-cGC, however, fails in the case of non-chiral compounds, such as 1,8-cineol. In this special case 1,8-cineol may be attributed to high-level Melaleuca varieties or to the fraudulent addition of Eucalyptus oil. In order to get reliable results, enantio-MDGC-MS analysis and/or IRMS measurements (as far as possible) are necessary. 

Fig. 17.14 Simultaneous stereoanalysis of Lavandula oil constituents, using enantio-MDGC (standard mixture), a Preseparation of racemic compounds unresolved enantiomeric pairs of octan-3-ol (6, 7), frcms-linalool oxide (1, 2), oct-l-en-3-ol (9, 10), ds-linalool oxide (3, 4), camphor (5, 8), linalool (17, 18), linalyl acetate (11, 12), terpinen-4-ol (15, 16) and lavandulol (13, 14). b Chiral resolution of enantiomeric pairs, transferred from the precolumn trans-linalool oxide 1 (2S,5S), 2 (2R,5R) ds-linalool oxide 3 (2R,5S), 4 (2S,5R) camphor 5 (IS), 8 (IR) octan-3-ol 6 R, 7S oct-1-en-3-ol PS, 10 R linalyl acetate 11 R, 12 S lavandulol 13 R, 14 S terpinen-4-ol 15 R, 16 S linalool 17 R, 18 S. [75]...

Bicchi C, Cordero C, lori C, Rubiolo P, Sandra P (2000) Headspace sorptive extraction (HSSE) in the headspace analysis of aromatic and medicinal plants. J High Resol Chromatogr 23 539 KreckM, Scharrer A, Bilke S, Mosandl A (2001) Stir bar sorptive extraction (SBSE)—enantio-MDGC-MS, a rapid method for the enantioselective analysis of chiral flavour compoimds in strawberries. Eur Food Res Technol 213 389... 

Sewenig S, Bullinger D, Hener U, Mosandl A (2005) Comprehensive authentication of (E)-a(/ )-ionone from raspberries, using constant flow MDGC-C/P-IRMS and enantio-MDGC/... 

In particular, enantioselective multidimensional gas chromatography (enantio-MDGC) with the combination of a non-chiral precolumn and a chiral main column... 

A schematic diagram of enantio-MDGC, well proved in quality assurance and origin control of flavourings and fragrances is outlined in Fig. 6.24. 

Furthermore, enantio-MDGC, employing heart-cutting techniques from DB-1701 as the preseparation column on to heptakis (3-0-acetyl-2,6-di-0-pentyl)-P-cyclodextrin as the chiral main column, was described by Mosandl et al. /2S7 as a powerful tool in the direct enantiomer separation of chiral y-lactones from complex matrices without any further clean-up or derivatization procedures. 

Likewise, chiral 5-lactones are known as characteristic flavouring compounds of fruits and dairy products /74y.Their stereodifferentiation was achieved with modified y-cyclodextrin by Konig et al. [84] and their chromatographic behaviour interpreted by coinjection with enantiopure references, as described by Palm et al. [36]. Using enantio-MDGC and the column combination OV 1701/octakis(3-O-butyryl-2,6-di-O-pentyl)-y-cyclodextrin the simultaneous stereodifferentiation of all aroma-relevant 4(5) alkylsubstituted y(5)-lactones has been reported recently [42, 85] (Fig. 6.30). 

Fig. 6.30 Simultaneous enantio-MDGC analysis of y(S) lactones, main column chromatogram of references (from ref [85])...

By means of enantio-MDGC analysis using the column combination SE 52 / DIME-P-CD in PS 268 the simultaneous stereodifferentiation of menthone (1,2) neomenthol (3, 4), isomenthone (5, 6) menthol (7, 8), neoisomenthol (9, 10) and menthyl acetate (11, 12) has been verified and applied to various peppermint oils (Fig. 6.35 Fig. 6.36). 

Fig, 6,35 Simultaneous enantio-MDGC analysis of chiral monoterpenoids from Mentha-species, pre column (A), main column (B) (from ref [94])... 

The (IR)-diastereomers emit a more intensive odour than the (IS)-configured compounds, but only the later diastereomers have been recognized to be peculiar to buchu leaf oil and reminiscent of blackcurrant. An enantio-MDGC method was developed. 

Fig, 6,40 Enantio-MDGC analysis of laboratory prepared huchu leaf oil A pre-column separation B main column separation limonene 1 (S), 2 (R) menthone 3 (IS, 4R) isomen-thone 6 (IS, 4S) pulegone 8 (S) cis-3-oxo-p-menthane-8-thiol 9 (IS, 4R) trans-3-oxo-p-menthane-8-thiol 12 (IS, 4S) trans-3-oxo-p-menthane-8-thiol acetate 14 (IS, 4S) cis-3-oxo-p-menthan-8-thiol acetate 15 (IS, 4R) (from ref [101])... 

Fig. 6.47 Enantio-MDGC analysis of a-ionone. Pre-column separation a(P) ionone (left) enantiomer separation of racemic a-ionone standard (right) (from ref [85, 114])...

Presently, online cGC-IRMS determination of 5 C and 5 H values of flavour compounds are established [107. 118-123] and, further on, 5 0 measurements using online cGC-IRMS procedures will be available. Finally, enantio-MDGC combined with multielement- and multicomponent IRMS methods will open the door to comprehensive authenticity assessment of natural flavour and fragrance compounds in the near future. 

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