Methodology Of Comprehensive Two-dimensional Gas Chromatography /Time-of-Flight Mass Spectrometry For Complex Sample Analysis

Comprehensive two-dimensional gas chromatography (GC×GC) is a highresolution and high sensitivity technique, which is invented over a decade ago.GC×GC with time-of-flight mass spectrometry (TOFMS) is especially suitable forthe separation and identification of analytes in complex mixtures. Focused on thecharacterization of complex mixtures, the following fundamental and applicationstudies using GC×GC have been carried out.A model has been developed for predicting the retention for comprehensivetwo-dimensional gas chromatography of any known mixtures. The model allows theprediction of temperature-programmed separation on the first dimension andisothermal separation on the second dimension as a function of experimentalconditions. Based on three isothermal runs, retention time and the bandwidth on bothdimensions are predicted for other conditions: any kind of linear temperatureprogram for programmed run on the first dimension, and different temperatures inthe case of isothermal runs on the second dimension. A method has been establishedfor the optimization of the temperature program of comprehensive two-dimensionalgas chromatography based on the prediction of the resolution ofdifficult-to-separatecomponents in the mixture. The optimum column temperature is output when theresolution of all the components of interest after GC×GC separation meets theresolution requirement and the running time is the shortest. The influences of someparameters (like column parameters, initial temperature, linear velocity, stationaryphase and the total peak capacity) on GC×GC separation were also discussed.Orthogonal separation is important to multidimensional chromatography. Theeffect of column combinations, initial temperature, heating rate, temperaturedifference of two columns on orthogonal separation were investigated. Factoranalysis was applied to the estimation of orthogonality in GC×GC separation. It isuseful in the selection of correct column combination. A method for generating the second dimension retention index in GC×GC hasbeen developed based on the prediction of retention data of n-alkanes at differenttemperatures. The method of characterization of complex system was studied,especially on processing of GC×GC/TOFMS data. Retention index in combinationwith TOFMS and the structured chromatogram of GC×GC increased reliability ofidentification. The different fractions of cigarette smoke were investigated by usingcomprehensive two-dimensional gas chromatography/time-of-flight massspectrometry. Over 1000 compounds, with S/N ≥100, including 139 organicacids and over 150 phenols were tentatively identified in the acidic fraction. A totalof 377 nitrogen-containing compounds, including 155 pyridine derivatives, 104quinoline/isoquinoine derivatives, and 56 pyrazine derivatives were tentativelyidentified in the basic fraction. A total of 250 phenols including 66 alkylphenolderivatives, 47 alkenylphenols, 57 naphthalenols, 17 phenylphenols, 32methoxyphenols, 9 acylphenols and 15 hydroxybenzadehydes were tentativelyidentified in the phenolic fraction. A total of 1800 hydrocarbons were tentativelyidentified in non-polar neutral fraction, including aliphatic hydrocarbons, aromatics,isoprenoid hydrocarbons. Finally, GC×GC was applied to quantitative analyses of important componentsin cigarette smoke condensate. A total of 41 nitrogen-containing compounds and 33neutral compounds were quantitatively detected. The quantitative results of 1DGCand GC×GC were compared. For the good separation components, the quantitativeresults of 1DGC method are in good agreement with those from GC×GC method.For the cigarette smoke condensates, the lack of sensitivity and resolution of 1DGCmethod often results in quantitative error.