ABSTRACT
Introduction ...................................................................................................... 22 Heart-cutting two-dimensional gas chromatography ................................ 23 Selectable one-dimensional or two-dimensional gas chromatography-mass spectrometry with simultaneous detection ........ 23
Instrumentation ........................................................................................... 24 Stir bar sorptive extraction ......................................................................... 25 Large volume full evaporation technique ............................................... 25 Selectable one-dimensional or two-dimensional gas chromatography-mass spectrometry with simultaneous olfactometry or element-speci€c detection .............................................. 27 Evaluation of simultaneous detection in selectable one-dimensional or two-dimensional gas chromatography-mass spectrometry ................ 30 Analysis of green note compound in whiskey by stir bar sorptive extraction-thermal desorption selectable one-dimensional or two-dimensional gas chromatography-mass spectrometry with simultaneous olfactometry ........................................................................ 32 Analysis of sulfur compounds in whiskey by large volume full evaporation technique-thermal desorption-selectable onedimensional or two-dimensional gas chromatography-mass spectrometry with simultaneous element-speci€c detection ................ 35
Selectable one-dimensional or two-dimensional gas chromatography-olfactometry/mass spectrometry with preparative fraction collection ....................................................................... 37 Conclusion ........................................................................................................ 44 Acknowledgments ........................................................................................... 44 References .......................................................................................................... 44
Introduction Gas chromatography-olfactometry (GC-O) is a valuable method for the selection of odor compounds from a complex mixture (Blank 2002). In particular, GC-O in combination with mass spectrometry (MS; GC-O/ MS) allows not only the evaluation of odor compounds but also their identi€cation with mass spectral information. However, many key odor compounds can occur at very low concentrations. Therefore, identi€- cation of odor compounds remains a hard task even with GC-O/MS because some compounds coelute with other analytes or the sample matrix, which leads to dif€culties when correlating the detected aroma with the correct compound. Multidimensional (MD) GC, more speci€cally, two-dimensional (2D) GC with simultaneous olfactometry and mass spectrometric detection, extends the identi€cation capability and separation resolution of GC. There are two established 2D GC approaches: (1) conventional heart-cutting 2D GC (GC-GC) (Bertsch 1990) and (2) comprehensive 2D GC (GCxGC) (Adahchour et al. 2006). The former approach is commonly used in target analysis of speci€c compounds in a sample. Heart-cutting 2D GC-MS with olfactometry can signi€cantly improve the identi€cation capability as well as the resolution of complex regions (Nitz, Kollmannsberger, and Drawert 1989; Pfannkoch and Whitecavage 2005). In contrast, the comprehensive 2D GC approach is mainly used in exhaustive analysis of a sample for total pro€ling. In the comprehensive approach, after a single introduction to the €rst column the entire sample is subjected to the two different separations (Adahchour et al. 2006). However, since GC run time in the second dimension of GCxGC is an order of magnitude faster than that in the €rst dimension (typically 3-5 s), it is very dif€cult to correlate a given odor perceived in GCxGC-O analysis to the peaks in the second dimension separation at this stage even after the €rst publication of GCxGC-O for the analysis of perfume (Zellner et al. 2007).
