Display omitted
•Pyrolysis of virgin and LDPE and PP wastes was performed in a pilot setup.•GC × GC was applied to identify and quantify the composition of the pyrolysis oils.•Identification of ...optimal temperature and pressure for pyrolysis.•The formation of preferentially propylene oligomers during PP pyrolysis.•Plastic contaminations such as PVC and biomass intensify the coke formation.
Due to the complexity and diversity of polyolefinic plastic waste streams and the inherent non-selective nature of the pyrolysis chemistry, the chemical decomposition of plastic waste is still not fully understood. Accurate data of feedstock and products that also consider impurities is, in this context, quite scarce. Therefore this work focuses on the thermochemical recycling via pyrolysis of different virgin and contaminated waste-derived polyolefin feedstocks (i.e., low-density polyethylene (LDPE), polypropylene (PP) as main components), along with an investigation of the decomposition mechanisms based on the detailed composition of the pyrolysis oils. Crucial in this work is the detailed chemical analysis of the resulting pyrolysis oils by comprehensive two-dimensional gas chromatography (GC × GC) and ICP-OES, among others. Different feedstocks were pyrolyzed at a temperature range of 430–490 °C and at pressures between 0.1 and 2 bar in a continuous pilot-scale pyrolysis unit. At the lowest pressure, the pyrolysis oil yield of the studied polyolefins reached up to 95 wt%. The pyrolysis oil consists of primarily α-olefins (37–42 %) and n-paraffins (32–35 %) for LDPE pyrolysis, while isoolefins (mostly C9 and C15) and diolefins accounted for 84–91 % of the PP-based pyrolysis oils. The post-consumer waste feedstocks led to significantly less pyrolysis oil yields and more char formation compared to their virgin equivalents. It was found that plastic aging, polyvinyl chloride (PVC) (3 wt%), and metal contamination were the main causes of char formation during the pyrolysis of polyolefin waste (4.9 wt%).
•Applications of IMS to natural product analysis since 2015 are reviewed.•Benefits of IMS in the analysis of secondary metabolites highlighted.•IMS may provide information not attainable by ...chromatography or MS.•Critical assessment of the advantages, limitations and future developments of IMS.
Ion mobility spectrometry (IMS) is a rapid separation technique capable of extracting complementary structural information to chromatography and mass spectrometry (MS). IMS, especially in combination with MS, has experienced inordinate growth in recent years as an analytical technique, and elicited intense interest in many research fields. In natural product analysis, IMS shows promise as an additional tool to enhance the performance of analytical methods used to identify promising drug candidates. Potential benefits of the incorporation of IMS into analytical workflows currently used in natural product analysis include the discrimination of structurally similar secondary metabolites, improving the quality of mass spectral data, and the use of mobility-derived collision cross-section (CCS) values as an additional identification criterion in targeted and untargeted analyses. This review aims to provide an overview of the application of IMS to natural product analysis over the last six years. Instrumental aspects and the fundamental background of IMS will be briefly covered, and recent applications of the technique for natural product analysis will be discussed to demonstrate the utility of the technique in this field.
•Use of comprehensive gas chromatography with dual detection for lipid analysis.•Elucidation of minor components in edible oils by comprehensive gas chromatography.•Oil fingerprint to extrapolate ...diagnostic information for authentication purpose.
The profile of minor compounds, such as alcohols, sterols, free and alkyl fatty acids, waxes, etc., was investigated in different vegetable oils by a comprehensive gas chromatographic system, coupled with a simultaneous dual detection (flame ionisation detector and mass spectrometer) for quantitative and qualitative purposes. Such a system generated a unique two-dimensional chromatogram to be used as a chemical fingerprint. Multi-level information, due not only to a more “comprehensive” preparation technique, but also thanks to the exploitation of a more powerful and sensitive analytical determination allowed the extrapolation of diagnostic information from the minor components profile of different vegetable oils, along with their characteristic profile. Furthermore, an admixture of an extra virgin olive oil with a low amount of sunflower and palm oils was evaluated, attesting to the powerful diagnostic information provided by the proposed approach.
•A review on analytical strategies for compounds in food and materials is described.•A tendency to integrate extraction and clean-up techniques was found.•SLE, PLE, SPME, FUSLE and Quechers are ...frequently used in package and food.•A trend towards the use of LC–HRMS for target and non-target analysis was observed.
In this review, we present current approaches in the analysis of food-packaging contaminants. Gas and liquid chromatography coupled to mass spectrometry detection have been widely used in the analysis of some relevant families of these compounds such as primary aromatic amines, bisphenol A, bisphenol A diglycidyl ether and related compounds, UV-ink photoinitiators, perfluorinated compounds, phthalates and non-intentionally added substances.
Main applications for sample treatment and different types of food-contact material migration studies have been also discussed. Pressurized Liquid Extraction, Solid-Phase Microextraction, Focused Ultrasound Solid-Liquid Extraction and Quechers have been mainly used in the extraction of food contact material (FCM) contaminants, due to the trend of minimising solvent consumption, automatization of sample preparation and integration of extraction and clean-up steps.
Recent advances in analytical methodologies have allowed unequivocal identification and confirmation of these contaminants using Liquid Chromatography coupled to High Resolution Mass Spectrometry (LC–HRMS) through mass accuracy and isotopic pattern applying. LC–HRMS has been used in the target analysis of primary aromatic amines in different plastic materials, but few studies have been carried out applying this technique in post-target and non-target analysis of FCM contaminants.
This review surveys different approaches for generating features from comprehensive two-dimensional chromatography for non-targeted cross-sample analysis. The goal of non-targeted cross-sample ...analysis is to discover relevant chemical characteristics (such as compositional similarities or differences) from multiple samples. In non-targeted analysis, the relevant characteristics are unknown, so individual features for all chemical constituents should be analyzed, not just those for targeted or selected analytes. Cross-sample analysis requires matching the corresponding features that characterize each constituent across multiple samples so that relevant characteristics or patterns can be recognized. Non-targeted, cross-sample analysis requires generating and matching all features across all samples. Applications of non-targeted cross-sample analysis include sample classification, chemical fingerprinting, monitoring, sample clustering, and chemical marker discovery. Comprehensive two-dimensional chromatography is a powerful technology for separating complex samples and so is well suited for non-targeted cross-sample analysis. However, two-dimensional chromatographic data is typically large and complex, so the computational tasks of extracting and matching features for pattern recognition are challenging. This review examines five general approaches that researchers have applied to these difficult problems: visual image comparisons, datapoint feature analysis, peak feature analysis, region feature analysis, and peak-region feature analysis.
► Volatile composition of Pinotage wines were investigated using SPME-GC
×
GC-TOFMS. ► 206 Compounds have been identified in nine Pinotage wines. ► Most of the compounds are reported for the first ...time in Pinotage wines.
As part of the ongoing research into the chemical composition of the uniquely South African wine cultivar Pinotage, the volatile composition of nine young wines of this cultivar was investigated using comprehensive two-dimensional gas chromatography (GC
×
GC) in combination with time-of-flight mass spectrometry (TOFMS). Headspace solid phase micro-extraction (HS-SPME) using a carboxen/polydimethylsiloxane (CAR/PDMS) fibre was used to extract the volatile compounds from the wine matrix. Extracts were analysed using an in-house developed GC
×
GC system equipped with a single jet, liquid nitrogen-based cryogenic modulator. In the current study, 206 compounds previously reported in wine and related matrices have been detected in nine Pinotage wines. Positive identification for 48 compounds was performed using authentic standards, while tentative identification of 158 compounds was based on deconvoluted mass spectra and comparison of linear retention indices (LRI) with literature values. Identified compounds included esters, alcohols, aldehydes, ketones, acids, acetals, furans and lactones, sulphur compounds, nitrogen compounds, terpenes, hydrocarbons, volatile phenols and pyrans. Volatile compounds potentially capable of influencing wine aroma are highlighted. Many of the compounds were common to all 9 wines, although volatile components unique to specific samples were also observed. The results represent the most detailed characterisation of volatile constituents of this cultivar reported to date.
► GC×GC–TOFMS was used to analyze VOCs in gravesoils. ► A group of specific functionalized compounds was found below the carcass. ► A group of specific methyl-branched alkanes was found at all depths ...of gravesoils. ► A depth trend in the amount of the specific alkanes was observed in gravesoils. ► A script was used to screen for cadaveric decomposition signature in soil samples.
This article reports on the use of comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–TOFMS) for forensic geotaphonomy application. Gravesoil samples were collected at various depths and analyzed for their volatile organic compound (VOC) profile. A data processing procedure was developed to highlight potential candidate marker molecules related to the decomposition process that could be isolated from the soil matrix. Some 20 specific compounds were specifically found in the soil sample taken below the carcass and 34 other compounds were found at all depths of the gravesoil samples. The group of the 20 compounds consisted of ketones, nitriles, sulfurs, heterocyclic compounds, and benzene derivatives like aldehydes, alcohols, ketones, ethers and nitriles. The group of the 34 compounds consisted of methyl-branched alkane isomers including methyl-, dimethyl-, trimethyl-, tetramethyl-, and heptamethyl-isomers ranging from C12 to C16. A trend in the relative presence of these alkanes over the various layers of soils was observed, with an increase in the amount of the specific alkanes when coming from the carcass to the surface. Based on the specific presence of these methyl-branched alkanes in gravesoils, we created a processing method that applies a specific script to search raw data for characteristic mass spectral features related to recognizable mass fragmentation pattern. Such screening of soil samples for cadaveric decomposition signature was successfully applied on two gravesoil sites and clearly differentiates soils at proximity of buried decaying pig carcasses from control soils.
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. None the less, routine use of GC × GC in forensic laboratories has been limited largely by (1) legal and regulatory guidelines, (2) lack of chemometrics training, and (3) concerns about the reproducibility of GC × GC. The goal of this review is to highlight recent advances in one-dimensional GC (1D-GC) and GC × GC analyses of fuels for compliance and forensic applications, to assist scientists in overcoming the aforementioned hindrances. An introduction to 1D-GC principles, GC × GC technology (column stationary phases and modulators) and several chemometric methods is provided. More specifically, chemometric methods will be broken down into (1) signal preprocessing, (2) peak decomposition, identification and quantification, and (3) classification and pattern recognition. Examples of compliance and forensic applications will be discussed with particular emphasis on the demonstrated success of the employed chemometric methods. This review will hopefully make 1D-GC and GC × GC coupled with chemometric data analysis tools more accessible to the larger scientific community, and aid in eventual widespread standardization.
Display omitted
•Gas chromatography is a standard forensic technique for fuel analysis.•GC × GC limited to research due to legal criteria and lack of funding in crime lab.•Higher-dimensional GC data benefits from chemometrics for interpretation.•Separation conditions affect the suitability of resulting data for chemometrics.•Mass spectrometry enhances the amenability of the data for chemometric analysis.
•Extraction of cork macerates with PDMS-coated SBSE followed by GC-GC-(NCI)MS.•The method reaches LOD below the odor threshold for all 12 compounds.•Linearity, intra- and inter-day precision and ...accuracy (89-126%) were satisfactory.•Correlations between several halophenols and haloanisoles were observed.
A method has been developed for the quantitative determination in cork bark macerates of 7 halophenols and 5 haloanisoles with demonstrated or suspected contribution to the cork taint off-flavour. Macerates were extracted with stirbar (20 mm polydimethylsiloxane-coated) sorptive extraction under optimized conditions (pH 3.5, 20% NaCl and 60 min). The bars were analysed by automated thermal desorption, heart-cutting two-dimensional gas chromatography and negative chemical ionization-mass spectrometry. Matrix effects were compensated for by a “matrix matched” calibration curve. Limits of detection were in the range 0.03-0.24 ng L−1, below the corresponding odor thresholds. Linearity (0.983 ≤ R2 ≤ 0.998), intra- and inter-day precision (5.4-14.3%) and accuracy (89–126%) were satisfactory. The analysis of 48 natural cork bark samples affected/not-affected bya cryptogamic disease (yellow spot) revealed compositional differences in 2,4,6-trichloroanisole (2,4,6-TCA), 2,4,6-trichlorophenol (2,4,6-TCP) and also in 2,6-dibromophenol, 2,3,4- and 2,4,5-TCP, 2,3,4-TCA and 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP). In addition, the contents of 2,4,6-TCP and 2,4,6-TCA, and 2,3,4,6-TeCP and some TCPs presented strong linear correlations.
Fully synthetic jet fuel (FSJF) produced via Fischer–Tropsch (FT) technology was recently approved by the international aviation fuel authorities. To receive approval, comparison of FSJF and ...crude-derived fuel and blends on their qualitative and quantitative hydrocarbon composition was of utmost importance. This was performed by comprehensive two-dimensional gas chromatography (GC
×
GC) in the reversed phase mode. The hydrocarbon composition of synthetic and crude-derived jet fuels is very similar and all compounds detected in the synthetic product are also present in crude-derived fuels. Quantitatively, the synthetic fuel consists of a higher degree of aliphatic branching with less than half the aromatic content of the crude-derived fuel. GC
×
GC analyses also indicated the presence of trace levels of hetero-atomic impurities in the crude-derived product that were absent in the synthetic product. While clay-treatment removed some of the impurities and improved the fuel stability, the crude-derived product still contained traces of cyclic and aromatic S-containing compounds afterwards. Lower level of aromatics and the absence of sulphur are some of the factors that contribute to the better fuel stability and environmental properties of the synthetic fuel. GC
×
GC was further applied for the analysis of products during Jet Fuel Thermal Oxidation Testing (JFTOT), which measures deposit formation of a fuel under simulated engine conditions. JFTOT showed the synthetic fuel to be much more stable than the crude-derived fuel.
PDF
