Abstract
An integrated system having the combined capability to perform gas chromatography (GC), comprehensive two-dimensional GC (GC x GC), and target heart-cut multidimensional GC (MDGC) using olfactometry (O), flame ionization (FID), and/or mass spectrometry (MS) detection is described. This combines a number of contemporary GC methods into a single instrument to provide very high resolution profiling of a sample. This provides initial assessment of volatile compound composition through GC x GC analysis with FID, which can be correlated with GC analysis using parallel O and FID detection. Subsequent microfluidic (Deans) switching selects regions (heart-cuts) of the chromatographic elution from the first dimension (D-1) column for further resolution on a long second dimension (D-2(L)) column for parallel detection of O and MS. Various D-2(L) operational conditions, as well as the effect of different heart-cut (H/C) duration, were compared. The favored mode involves cryotrapping of heart-cuts, cooling the oven, and reducing carrier flow to offer greater efficiency. An analytical strategy that incorporates GC-FID/O, GC x GC-FID, and MDGC-MS/O analyses with cumulative solid phase microextraction (SPME) sampling for volatile sample enrichment is presented in this work. Excellent qualitative and quantitative performance was demonstrated with a Shiraz wine sample and an allergens mixture, with tentative identification of acetic acid, octen-3-ol, and ethyl octanoate as aroma contributors in Shiraz wine and determination of beta-damascenone (floral odor) well separated from hexanoic acid (sweaty odor). A novel approach to obtain D-2 retention indices is reported, allowing matching of mass spectral, I-1 (retention index in D-1) and I-2 (retention index in D-2) data. The method employs the same olfactory detector at the end of the D-1 and D-2(L) columns.