Flow-modulation comprehensive two-dimensional enantio-gas chromatography: A valid and flexible alternative to heart-cutting multidimensional enantio-gas chromatography.

The present research is focused on the proposal of use of flow-modulation comprehensive two-dimensional enantio-gas chromatography (FM eGC × GC) as a valid, flexible, and possibly superior alternative to heart-cutting multidimensional enantio-GC (eMDGC). The latter, a technique of demonstrated utility, is used specifically for the targeted separation of chiral compounds, whereas FM eGC × GC can produce both targeted and high-resolution untargeted information in a single run. It is clearly possible to use eMDGC for untargeted analysis, often with a flame ionization detector (stand-by analysis), to monitor a first-dimension (1D) separation, of much lower peak capacity compared to FM eGC × GC. If eMDGC is used with mass spectrometry (MS), it is normally exploited to monitor the second-dimension (2D) separation. The analytical instrument consisted of automated solid-phase microextraction (SPME), and a low duty-cycle FM eGC × GC system (with time-of-flight MS), equipped with an enantioselective 1D column (2,3-di-O-methyl-6-t-butyl silyl ß-cyclodextrin derivative) and a 2D polyethylene glycol one. Ten Marsala wines were subjected to analysis, for the determination of chiral lactones (many at the low ppb level, due to the high concentration capacity of SPME) and for general analyte profiling. In many instances, highly complex chromatograms were attained, with statistical analysis (ANOVA-simultaneous component analysis and partial least squares discriminant analysis) used for sample differentiation.

Automated sample preparation and fast GC-MS determination of fatty acids in blood samples and dietary supplements.

The present research is focused on the optimization of an automatized sample preparation and fast gas chromatography-mass spectrometry (GC-MS) method for the analysis of fatty acid methyl esters (FAMEs) in blood samples and dietary supplements, with the primary objective being a significant reduction of the analysis time and, hence, an enhanced sample throughput. The mass spectrometer was operated in the scan/selected ion monitoring (SIM) acquisition method, thus enabling the obtainment of qualitative and (highly sensitive) quantitative data. The separation of FAMEs was obtained in about 11 min by using a micro-bore column of dimensions 15 m × 0.10 mm ID × 0.10 µm df with a polyethylene glycol stationary phase. The novelty of the research involves reducing analysis time by using the novel fast GC-MS method with increased identification reliability and sensitivity in a single chromatographic run. With regard to the figures of merit, linearity, accuracy, and limits of detection (LoD) and quantification (LoQ) were determined. Specifically, regression coefficients were between 0.9901 and 0.9996; the LoDs ranged from 0.05 to 1.02 µg g-1 for the blood analysis method, and from 0.05 to 0.26 mg g-1 in the case of the dietary supplement approach. With respect to LoQs, the values were in the ranges of 0.15-3.39 µg g-1 and 0.15-0.86 mg g-1 for blood and dietary supplements analysis methods, respectively. Accuracy was evaluated by analyzing certified reference materials (human plasma, fish oil).

Flow-modulated comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry: use of hydrogen as a more sustainable alternative to helium.

The present research is focused on the use and evaluation of hydrogen, as a more sustainable alternative to helium, within the context of fast flow modulation comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. In such a respect, a comparison was made between the two mobile phases in terms of speed and overall chromatography performance. All experiments were carried out by using the following column set: low polarity with dimensions 10 m × 0.25 mm ID × 0.25 µm df and medium polarity with dimensions 2 m × 0.10 mm ID × 0.10 µm df. Fundamental gas chromatography parameters (efficiency, resolution) were measured under different experimental conditions, using the two carrier gases. Efficiency was measured in both the first and second dimensions, using a probe compound under isothermal conditions; after defining the optimum carrier gas conditions, a mixture containing 20 pesticides was analyzed to measure resolution, again in the first and second dimensions, using a temperature program. It was found (as expected) that a similar chromatography performance could be attained when using hydrogen, albeit with a circa 25% reduction in analysis time. Signal-to-noise ratios of the pesticides were calculated, using both carrier gases, with such values generally reduced (on average by 14%) when using hydrogen. Finally, a comparison was made between mass spectral profiles obtained analyzing the pesticides and fatty acid methyl esters using the two mobile phases. Even though mass spectral differences were observed, the ion profiles could be considered generally similar.

Untargeted profiling and differentiation of geographical variants of wine samples using headspace solid-phase microextraction flow-modulated comprehensive two-dimensional gas chromatography with the support of tile-based Fisher ratio analysis.

The volatile fraction of food, also called the food volatilome, is increasingly used to develop new fingerprinting approaches. The characterization of the food volatilome is important to achieve desired flavor profiles in food production processes, or to differentiate different products, with winemaking being one popular area of interest. In the present research, headspace solid-phase microextraction (HS SPME) coupled to flow-modulated comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (FM GC×GC-TOFMS) was used to characterize geographical-based differences in the volatilome of five white "Grillo" wines (of Sicilian origin), comprising the five sample classes. All wines were produced with the same vinification method in 2019. To minimize the influence of minor bottle-to-bottle differences, three bottles of the same wine were randomly selected, and three samples were collected per bottle, resulting in nine sample replicates per wine. Particular emphasis was devoted to the operational conditions of a novel low duty cycle flow modulator. A fast FM GC×GC-TOFMS method with a modulation period of 700 ms and a re-injection period of 80 ms was developed. Following, the instrumental software was exploited to identify class-distinguishing analytes in the dataset via tile-based Fisher ratio analysis (i.e., ChromaTOF Tile). A tile size of 10 modulations (7 s) on the first dimension and 45 spectra (300 ms) on the second dimension was used to encompass average peak widths and to account for minor retention time shifting. Off-line software was used to apply an ANOVA test. A p-value of 0.01 was applied in order to select the most important class-distinguishing analytes, which were input to principal component analysis (PCA). The PCA scores plot showed distinct clustering of the wines according to geographical origin, although the loadings revealed that only a few analytes were necessary to differentiate the wines. However, a comprehensive flavor profile assessment underscored the importance of all the information output by the ChromaTOF Tile software.