Enabling cuboid-based fisher ratio analysis using total-transfer comprehensive three-dimensional gas chromatography with time-of-flight mass spectrometry.

Comprehensive three-dimensional (3D) gas chromatography with time-of-flight mass spectrometry (GC-TOFMS) is a promising instrumental platform for the separation of volatiles and semi-volatiles due to its increased peak capacity and selectivity relative to comprehensive two-dimensional gas chromatography with TOFMS (GC×GC-TOFMS). Given the recent advances in GC-TOFMS instrumentation, new data analysis methods are now required to analyze its complex data structure efficiently and effectively. This report highlights the development of a cuboid-based Fisher ratio (F-ratio) analysis for supervised, non-targeted studies.

Tailoring Amphiphilic Copolymers for Improved Aqueous Foam Stability.

Amphiphilic copolymers of various-molecular-weight (MW) poly(ethylene glycol) (PEG) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The first PEG series, poly(ethylene glycol)monomethacrylate (PEGMA, average Mn 200 and 400 MW), contained an -OH terminal group, and the second series, poly(ethylene glycol) monomethyl ether monomethacrylate (PEGMMA, average Mn 200, 400, and 1000 MW), possessed an -OCH terminal group. A total of five PEG-functionalized copolymers contained the same hydrophobic monomer, butyl acrylate (BA), and were successfully reproduced via a one-pot synthesis.

Tile-based variance rank initiated-unsupervised sample indexing for comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry.

Tile-based variance rank initiated-unsupervised sample indexing (VRI-USI) analysis is introduced for comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS). VRI-USI analysis addresses the challenge that irrelevant variables can often obscure true chemical variation when using other unsupervised chemometric tools. Implementation of VRI-USI analysis with GC×GC-TOFMS data incorporates the tile-based Fisher ratio (F-ratio) analysis software platform that mitigates the effects of retention shifting in both separation dimensions with an unsupervised variance metric (instead of the F-ratio metric) as the initial step of ranking the hitlist.

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.

Class comparison enabled mass spectrum purification for comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

Tile-based Fisher ratio (F-ratio) analysis is emerging as a versatile data analysis tool for supervised discovery-based experimentation using comprehensive two-dimensional (2D) gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS). None the less, analyte identification can often be marred by poor 2D resolution and low analyte abundance relative to overlapping compounds. Linear algebra-based chemometric methods, in particular multivariate curve resolution alternating least squares (MCR-ALS), parallel factor analysis (PARAFAC) and PARAFAC2, are often applied in an effort to address this situation.

Baseline correction method for dynamic pressure gradient modulated comprehensive two-dimensional gas chromatography with flame ionization detection.

A baseline correction method is developed for comprehensive two-dimensional (2D) chromatography (GC × GC) with flame-ionization detection (FID) using dynamic pressure gradient modulation (DPGM). The DPGM-GC × GC-FID utilized porous layer open tubular (PLOT) columns in both dimensions to focus on light hydrocarbon separations. Since DPGM is nominally a stop-flow modulation technique, a rhythmic baseline disturbance is observed in the FID signal that cycles with the modulation period (P).

Development of variance rank initiated-unsupervised sample indexing for gas chromatography-mass spectrometry analysis.

Traditional non-targeted chemometric workflows for gas chromatography-mass spectrometry (GC-MS) data rely on using supervised methods, which requires a priori knowledge of sample class membership. Herein, we propose a simple, unsupervised chemometric workflow known as variance rank initiated-unsupervised sample indexing (VRI-USI). VRI-USI discovers analyte peaks exhibiting high relative variance across all samples, followed by k-means clustering on the individual peaks.

Investigation of the limit of discovery using tile-based Fisher ratio analysis with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry.

Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) is followed by tile-based Fisher ratio (F-ratio) analysis to investigate the "limit of discovery" for low concentration levels of sulfur-containing compounds in JP8 jet fuel. A mixture of 14 sulfur-containing compounds was spiked at 30 ppm, 15 ppm, 3 ppm and 1.5 ppm into the neat fuel prior to GC×GC-TOFMS analysis with a "reversed" column format (aka polar first dimension (D) and non-polar second dimension (D) column).

Total-transfer comprehensive three-dimensional gas chromatography with time-of-flight mass spectrometry.

Although comprehensive two-dimensional (2D) gas chromatography (GC × GC) is a powerful technique for complex samples, component overlap remains likely. An intriguing route to address this challenge is to utilize the additional peak capacity and chemical selectivity provided by comprehensive three-dimensional (3D) gas chromatography (GC), especially with time-of-flight mass spectrometry detection (GC-TOFMS). However, the GC-TOFMS instrumentation reported to date has employed one or both modulators with a duty cycle < 100%, making the potential gain in detection sensitivity over GC × GC modest, or perhaps even worse.

Development of gas chromatographic pattern recognition and classification tools for compliance and forensic analyses of fuels: A review.

Gas chromatography (GC) is undoubtedly the analytical technique of choice for compositional analysis of petroleum-based fuels. Over the past twenty years, as comprehensive two-dimensional gas chromatography (GC × GC) has evolved, fuel analysis has often been highlighted in scientific reports, since the complexity of fuel analysis allows for illustration of the impressive peak capacity gains afforded by GC × GC. Indeed, several research groups in recent years have applied GC × GC and chemometric data analysis to demonstrate the potential of these analytical tools to address important compliance (tax evasion, tax credits, physical quality standards) and forensic (arson investigations, oil spills) applications involving fuels.

Impact of data bin size on the classification of diesel fuels using comprehensive two-dimensional gas chromatography with principal component analysis.

Principal component analysis (PCA) is a widely applied chemometric tool for classifying samples using comprehensive two-dimensional (2D) gas chromatography (GC × GC) separation data. Classification via PCA can be improved by 2D binning of the data. A "standard operating procedure (SOP) bin size" is often applied to improve the S/N and to mitigate potential retention time misalignment issues.

Ultrafast separations via pulse flow valve modulation to enable high peak capacity multidimensional gas chromatography.

Ultrafast modulation with a modulation period P ≥ 50ms via a pulse flow valve is demonstrated for comprehensive two-dimensional gas chromatography (GC×GC) and comprehensive three-dimensional (3D) gas chromatography (GC). Significant increases in peak capacity and peak capacity production are achieved for GC×GC and GC relative to previous studies due to using pulse flow valve modulation. Due to the nature of the "partial" modulation process, the separation dimension following pulse flow valve modulation is not a traditional chromatogram, rather requires data processing to convert the data to expose the encoded chromatographic information, producing "apparent" chromatographic peaks.