Use of advanced sample preparation and multidimensional gas chromatography-mass spectrometry methods within the context of food and biological sample analyses

The main aim of the research, described in the present Ph.D. thesis, is based on the development of advanced gas chromatography-mass spectrometry methods and sample preparation protocols for the characterization and investigation of complex biological and food samples. Currently, one-dimensional (1D) gas chromatography (GC) is widely exploited and is a powerful separation technique for the separation of volatile and semi-volatile compounds. However, sample complexity can often exceed the capacity of the separation system. In fact, considering that one 1D GC separations often rely on a single separation criterion, such as the different volatility of the analytes, if the vapour pressure of several analytes in a mixture are not sufficiently different, then coelution(s) will occur. In such a respect, the application of multidimensional analytical methods is a suitable alternative in cases of high sample complexity. Comprehensive 2D GC (GC×GC) was first described in 1991, when Liu and Phillips employed dual-stage thermal modulation to achieve a GC×GC separation. The introduction of GC×GC, can be considered as one of the most important evolutions in the field of GC. Since its appearance, many developments have been made in this field in terms of hardware, software, and practical/theoretical studies. In terms of published research, the use of GC was exploited for the analysis of fatty acids in dietary supplements and blood samples. In detail, a robotic preparative station enabled automatic derivatization in a fully automatic manner. Fatty acid derivatization was performed by using a direct derivatization protocol. The separation was achieved by using a medium-polarity ionic liquid column and dual detection was carried out to obtain quali-quantitative results in a single run. A further study was focused on the use of GC×GC combined with time-of-flight mass spectrometry (ToFMS) to characterize geographical-based differences in the volatilome of five white "Grillo" wines (of Sicilian origin), forming five sample classes. The technique generates a high quantity of data that should be transformed into useful information after data processing with chemometric approaches. Specifically, Fisher ratio analysis (F-ratio analysis) was applied to find the class- distinguishing analyte features, followed by the use of Principal Component Analysis as a tool to visualize the success of the F-ratio analysis. In another research, hydrogen was evaluated as a more sustainable alternative to helium, within the context of fast flow modulation (FM) GC×GC-ToFMS. In such a respect, a comparison was made between the two mobile phases in terms of speed and overall chromatography performance (efficiency, resolution). Finally, mass spectral profiles obtained analyzing pesticides and fatty acid methyl esters using the two mobile phases were compared. In addition, a greener and more sustainable methodology was developed for Capsicum volatilome investigation by means of headspace solid-phase microextraction (HS SPME) coupled with FM GC×GC-ToFMS using hydrogen as carrier agas. A tile-based Fisher-ratio software was used to easily determine compounds that varied the most within the same variety of Capsicum samples. Particular emphasis was also devoted to the aroma profile of the thirty most sample- distinguishing compounds. In a later period of the PhD course, focus was devoted to the targeted determination of chiral lactones, along with the untargeted characterization of the volatile fraction of Marsala wines through HS SPME combined with FM GC×GC-ToFMS (enantioselective column×polar column), using hydrogen as carrier gas. Lactones are important constituents of food and beverage aromas and are markers of alcoholic beverages aged in wood barrels. In such a respect, and considering important aspects related to food authenticity, their determination can provide information on such aging processes. During the Ph.D. course, I spent six months at ESPCI Paris (École Supérieure de Physique et de Chimie Industrielles) to develop solid supports functionalized with target-specific oligonucleotides, commonly known as aptamers, for the selective extraction of mycotoxins present in biological samples.