When the major process of separation for each column is different (e.g., boiling point, polarity, shape selection), orthogonal separation can be achieved. The main advantage of this technique is that columns of distinctly different phases can be used, thus providing significantly enhanced chromatographic separation. The slices can be reconstructed as either a virtual three-dimensional (contour plot) plot ( Figure 3.2c, top) or two-dimensional color intensity plot ( Figure 3.2c, bottom). The slices are minichromatograms that are detected in real time as shown in Figure 3.2b, where each slice or minichromatogram originates from a separate modulation cycle- P M. The coeluting peak ( X+ Y) in the primary column is cut into “slices” (secondary chromatograms) by the modulator and on the secondary column are separated into X and Y. Recent applications in food-related topics include the investigation of the impact of malolactic fermentation on the volatile composition of Pinotage wines ( Vestner et al., 2011) and the analysis of volatile compounds in cacao beans and its quality control ( Humston et al., 2009).įigure 3.2a shows a schematic of a comprehensive GC×GC system where all of the analytes exiting the primary column 1D are condensed by the modulator from which they are reinjected into the secondary column 2D. TOF-MS provides high data acquisition speed suitable to GC × GC even though high-speed Q is nowadays available. GC × GC provides much higher peak capacity, better separation power, and enhanced sensitivity. The modulator continuously collects small fractions of the effluent from the first column, which is quickly transferred to the second column.
#CHROMATOGRAM VIEWER RPT SERIES#
In GC × GC, compounds are separated on two columns of different selectivity connected in series by a modulation device. Nowadays, in a single GC run, it is possible to analyze hundreds of trace compounds in food products such as environmental contaminants or pesticides.Ĭomprehensive two-dimensional GC (GC × GC) coupled to fast acquisition MS (mostly TOF-MS) facilitates the analysis of very complex matrix, that is components of essential oils, residual pesticides, or contaminants in food products. Furthermore, MS/MS instruments facilitate the development of multi-residue analysis of pesticides. The system provided higher selectivity, resulting in less interference from co-eluting compounds and matrix and consequently, a better signal-to-noise (S/N), allowing quantitation with lower limits of quantitation. For the detection and quantification of target compounds in complex matrices at trace levels, GC coupled to triple quadrupole-MS is a very powerful instrument providing greater selectivity and sensitivity than single quad MS. GC–MS following derivatization is used in the quantification of several food constituents such as carbohydrates or phenolic acids in fruits and vegetables. MS is ideally coupled to GC, for example GC is the “classical” method for the determination of fatty acid composition, but only the coupling with MS, allowing identification of the number of double bonds, can provide peak assignment and compound identification.ĭepending on the scope of the analysis, different GC–MS solutions are nowadays available. GC–MS is the method of choice for VOCs analysis and for routine qualitative and/or quantitative determination of components such as fatty acids, sterols, alcohols, oils, and low mass carbohydrates and for the detection and quantification of a large number of contaminants. GC–MS is extensively used for the analysis of such complex matrices. Furthermore, different sources of contaminants such as pesticides, environmental pollutants, natural toxins, veterinary drugs, and packaging materials can taint foodstuffs. As a result, GC-MS is considered a “gold standard” for substance identification and the method of choice, the method required by the regulatory authorities for a wide number of analyses of high significance such as the analysis of pharmaceuticals/drugs of abuse, steroids and hormones, contaminants, and other analytes.įood products are usually complex matrixes made of organic or inorganic substances that consist of essential body nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. In the analysis of small volatile molecule, GC–MS is unsurpassed in sensitivity, efficiency, and productivity. A major advantage of GC over other separation methods (e.g., liquid chromatography (LC)) is its simplicity and higher separation power. GC can separate compounds and MS can provide specific, sensitive detection and structural information. GC-MS combines the features of GC with those of MS. Georgios Theodoridis, in Chemical Analysis of Food (Second Edition), 2020 4.1 Gas chromatography mass spectrometry in food analysis