Chromatographic Fingerprinting and Accurate Quantitative Profiling by Multiple Headspace Solid Phase Microextraction and Differential-Flow Modulated Comprehensive Two-Dimensional Gas Chromatography: The Aroma Blueprint of Extra Virgin Olive Oil

The role of sample preparation, as key-step of the analytical method and as zeroth dimension of the system, is crucial and its design is strictly dependent on the method’s final objectives (e.g., untargeted fingerprinting or targeted profiling). In the study of the complex food volatilome, comprehensive two-dimensional gas chromatography combined to mass spectrometric detection (GC×GC-MS), has demonstrated to be very effective on both untargeted and targeted investigations, while combining high-throughput fingerprinting to quantitative profiling on the same analytical batch [1]. In this study we make a step forward in the exploitation of headspace solid-phase microextraction (HS-SPME) GC×GC-MS potentials, by designing a procedure capable of performing a comprehensive chromatographic fingerprinting of the complex volatile fraction of high-quality extra-virgin olive oil (EVOO) while providing accurate quantitative data on a large set of targeted analytes (i.e., targeted quantitative profiling [2]) with an informative role related to samples sensory quality and qualification – the so called aroma blueprint [3]. Moreover, the procedure is designed for full automation and is based on robust, reliable, commercially available analytical platform, suitable for high-throughput screenings and quality control assessment. For these reasons, the differential-flow modulation technology is here chosen as core element of the GC×GC platform, because of its stable performances and relative ease of use [2]. On the other hand, to achieve accurate quantitative results accompanied by low limits of quantitation (LOQs), the multiple headspace extraction (MHE) approach is combined to the enrichment capacity of SPME with a multi-component fiber. The challenging aspect of the MHS-SPME procedure rely on the need of avoiding headspace saturation, at the basis of quantitation inaccuracy of some HS methods, while enabling multi analyte quantitation with a relatively simple calibration procedure. Method’s figures of merit include analytes identity confirmation, by EI-MS spectral signature and two retention time points (1tR and 2tR), and accuracy in quantitative determinations based on external calibration and results crossvalidation within two paralleled detectors (i.e., MS and flame ionization detector FID). Moreover, parallel detection by MS/FID, enables the extension of the method linearity range over three order of magnitude and opens to the possibility of adopting predicted FID relative response factors (RRFs) for quantitative estimations. Results are critically evaluated in light of their fingerprinting potential over a set of fifty EVOO samples from Italian top-quality production [5], obtained from different olives cultivars and from three harvest regions. Quantitative data on 39 targeted analytes are compared to those achieved by applying single level internal standardization (IS), which does not consider, above all, analytes HS partition constants (KHS) and accumulating polimer/material distribution constant (KD) under the applied sampling conditions. The aroma blueprint of EVOOs from Garda lake region, Sicily and Tuscany is therefore delineated and the signature of quality objectified.