Automating data analysis for two-dimensional gas chromatography/time-of-flight mass spectrometry non‐targeted analysis of comparative samples

Abstract

Non-targeted analysis of environmental samples, using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC/ToF-MS), poses significant data analysis challenges due to the large number of possible analytes. Non-targeted data analysis of complex mixtures is prone to human bias and is laborious, particularly for comparative environmental samples such as contaminated soil pre- and post-bioremediation. To address this research bottleneck, we developed OCTpy, a Python™ script that acts as a data reduction filter to automate GC × GC/ToF-MS data analysis from LECO ChromaTOF software and facilitates selection of analytes of interest based on peak area comparison between comparative samples. We used data from polycyclic aromatic hydrocarbon (PAH) contaminated soil, pre- and post-bioremediation, to assess the effectiveness of OCTpy in facilitating the selection of analytes that have formed or degraded following treatment. Using datasets from the soil extracts pre- and post-bioremediation, OCTpy selected, on average, 18% of the initial suggested analytes generated by the LECO ChromaTOF software Statistical Compare feature. Based on this list, 63-100% of the candidate analytes identified by a highly trained individual were also selected by OCTpy. This process was accomplished in several minutes per sample, whereas manual data analysis took several hours per sample. OCTpy automates the analysis of complex mixtures of comparative samples, reduces the potential for human error during heavy data handling and decreases data analysis time by at least tenfold.

Formation of Polycyclic Aromatic Hydrocarbon Oxidation Products in α-Pinene Secondary Organic Aerosol Particles Formed through Ozonolysis

“…Ozonolysis of aromatic compounds can lead to different substitutions on the PAH rings. , Thermodynamic calculations suggest that an OH adduction is favorable over carbonyl adductions due to the highly instable epoxide intermediates, both resulting in low-volatility products . PHE ozonolysis has previously been measured to form 2′-formyl­[1,1′-biphenyl]-2-carboxylate (2′F­(1-1′BP)­2C) in laboratory studies of PHE bound to the surface of silica particles .…”

Evaluating Computational and Structural Approaches to Predict Transformation Products of Polycyclic Aromatic Hydrocarbons

“…Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment, − and some are known to be carcinogenic, mutagenic, or toxic. − PAHs may be produced through geological processes or incomplete combustion of organic matter. , Atmospheric PAHs ,, undergo long-range atmospheric transport, − which has implications for human health worldwide . Furthermore, PAHs undergo phototransformation into PAH-transformation products (PAH-TPs) via reactions with atmospheric oxidants, such as hydroxyl radicals (OH • ) and nitrogen oxides (NOx).…”

Performance Evaluation of a Nontargeted Platform Using Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry Integrating Computer-Assisted Structure Identification and Automated Semiquantification for the Comprehensive Chemical Characterization of a Complex Matrix

“…Comprehensive two-dimensional ( 2 D) gas chromatographic separation (GC × GC) coupled with fast-scanning time-of-flight mass spectrometers (GC × GC–TOFMS) represents a well-established advanced field of gas chromatography/mass spectrometry (GC/MS) . GC × GC–TOFMS is currently recognized as the most powerful separation technique in gas chromatography (GC), and its routine application for the characterization of complex matrixes has been proven and published in numerous scientific reports. − However, despite advantages afforded by the use of comprehensive 2 D separation techniques, the large diversity of compounds in complex matrixes such as cigarette smoke cannot be fully resolved using a single analytical method. Most NTS applications require the use of multiple extraction and/or chromatographic methods that maximize the coverage of the chemical space for their application domain and, ideally, have some degree of overlap.…”