Implications of phase ratio for maximizing peak capacity in comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

Kinematic viscosity prediction of jet fuels and alternative blending components via comprehensive two-dimensional gas chromatography, partial least squares, and Yeo-Johnson transformation

This work presents an accurate yet simplified partial least squares model to predict the kinematic viscosity of conventional and alternative jet fuels at -20°C using comprehensive two-dimensional gas chromatography coupled to a flame ionization detector (GC × GC/FID). Three different normalization methods (mean-centering, logarithmic, and Yeo-Johnson) were evaluated to identify their impact in the prediction of middle distillates' physical properties. Results using Yeo-Johnson transformation exhibited improved viscosity prediction capabilities over the validation set with a mean absolute percentage error of 5.3%, a root-mean-squared error of 0.23, and a coefficient of determination (R2 ) of 0.9404 using only 10 latent variables. Unlike previously reported correlations, this model allowed the identification of specific hydrocarbon groups and carbon numbers that drive jet fuel viscosity at low temperatures. The presence of even small amounts of large branched-alkanes (C15 -C17 ), dicyclic-alkanes (C10 ), and cycloaromatics (C11 ) have the potential to strongly increase the kinematic viscosity of jet fuels. Contrastingly, light monocycloalkanes and branched-alkanes (≤ C10 ) were associated with lower viscosity values. Novelly, this model suggests the implementation of Yeo-Johnson transformations to predict the physical properties of middle distillates to further improve the performance metrics of partial least squares models based on GC data.

Second-Dimension Temperature Programming System for Comprehensive Two-Dimensional Gas Chromatography. Part 1: Precise Temperature Control Based on Column Electrical Resistance

A second-dimension temperature programming system (²DTPS) for comprehensive two-dimensional gas chromatography (GC × GC) is introduced, and its performance is characterized. In the system, a commercial stainless-steel capillary column was used for the separation, as a heating element, and as a temperature sensor. The second dimension (²D) column was resistively heated and controlled using an Arduino Uno R3 microcontroller. Temperature measurement was accomplished by measuring the overall ²D column's electrical resistance. A diesel sample was used to compare the ²D peak capacity (²n_c) and resolution (²R_s), while a perfume sample was used to compare the reproducibility of the system for within-day (n = 5) and day-to-day (n = 5) results. The ²n_c improved by 52% with the ²DTPS compared to the secondary oven. The GC × GC system utilizing the ²DTPS had an average within-day and day-to-day relative standard deviation (RSD) of 0.02 and 0.12% for the ¹D retention time (¹t_R), 0.56 and 0.58% for the ²D retention time (²t_R), and 1.18 and 1.53% for the peak area, respectively.

Characterization of the volatile profile of Chinese rice wine by comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry

BACKGROUND

Chinese rice wine (CRW) is a kind of traditional fermentation wine in China. Aged CRW is more popular among consumers owing to its harmonious and pleasant flavor. The volatile profile of CRW has been extensively studied using gas chromatography/mass spectrometry (GC/MS). However, flavor components in CRW are far richer than those detected by GC/MS. To obtain more information about the volatile profile of fresh (5-year) and aged (10-year) CRW, a method based on comprehensive two-dimensional gas chromatography coupled to quadrupole mass spectrometry (GC×GC/qMS) was developed. The major volatile compounds contributing to the characteristic aroma of fresh and aged CRW were identified by surrogate odor activity value (OAV).

RESULTS

Ninety-eight volatile compounds were detected in the 5-year CRW samples and 107 in the 10-year samples by GC×GC/qMS. The numbers of compounds detected by GC×GC/qMS for the 5-year and 10-year samples were 71.4 and 65.4% higher than those detected by GC/MS. The aged wine had a more complex volatile profile than the fresh wine, with an increase in esters and aldehydes and a decrease in alcohols and organic acids. There were 22 volatile compounds with surrogate OAV > 1. Nine were the potent key aroma compounds in CRW: ethyl isovalerate (OAV 500-33 500), ethyl butyrate (OAV 84-334), ethyl isobutyrate (OAV 49-170), 2-nonenal (OAV 20-100), ethyl heptanoate (OAV 1-74), ethyl hexanoate (OAV 60-77), phenylethyl alcohol (OAV 2-18), benzaldehyde (OAV 28-30) and hexanal (OAV 4-11).

CONCLUSION

GC×GC/qMS showed better separation than GC/MS. The presented GC×GC/qMS method was suitable for characterization of the volatile profile of CRW. © 2019 Society of Chemical Industry.

Advances in the application of comprehensive two-dimensional gas chromatography in metabolomics

Due to excellent separation capacity for complex mixtures of chemicals, comprehensive two-dimensional gas chromatography (GC × GC) is being utilized with increasing frequency for metabolomics analyses. This review describes recent advances in GC × GC method development for metabolomics, organismal sampling techniques compatible with GC × GC, metabolomic discoveries made using GC × GC, and recommendations and best practices for collecting and reporting GC × GC metabolomics data.