Recent advances in gas chromatography-mass spectrometry (GC-MS) (ionization sources at atmospheric pressure, fast GC, GCxGC, high resolution mass spectrometry, etc.) have significantly improved the ...capabilities of this technique, traditionally used to determine pesticides. Although liquid chromatography mass spectrometry (LC-MS/MS) is nowadays preferred, pyrethroids and organochlorine pesticides are more sensitive by GC-MS and a significant number of other pesticides work well by both techniques. Here, we critically review the development, instrumentation, approaches and applications of GC-MS, focusing on the analysis of pesticide residues published between 2000 and 2019 along with outstanding pioneer contributions, with special emphasis on those published after 2010. This review attempts to fill a void of information on the state-of-art of GC-MS for pesticide residue determination, describing the pros and cons of the different approaches, and the main applications.
•New advances in GC-MS focus on pesticide residue determination.•Improving separation speed by fast GC and resolving power by GC x GC.•High sensitive APCI ionization for labile pesticides and further MS/MS.•Improved identification for metabolites, unexpected or unknowns by HRMS.•Challenges and future perspectives of GC-MS in pesticide determination are addressed.
(Mass spectrometric) non-target screening is a preferably comprehensive and untargeted (predominantly organic molecules detecting) approach combining (robust) analytical measurements with adapted ...data evaluation concepts, systematic compound identification workflows, and statistical data interpretation. It is well suitable for the identification of new, unexpected and/or unknown organic compounds as well as monitoring ‘molecular fingerprints’ and profiling ‘process-relevant’ molecules via statistical methods. In recent years, 14 articles in various disciplines were published and presented in this Special Issue, whereby it contains 4 peer-reviewed review articles and 10 peer-reviewed research articles dealing with non-target screening strategies and solutions.
Summary
Cordyceps militaris chicken soup has always been one of the most popular Chinese‐style soups due to its high nutritional value and special flavour. In the present work, C. militaris chicken ...soup was stewed after enzymolysis pretreatment. Several advanced techniques including GC‐MS, GC × GC‐TOF MS and GC‐IMS were utilised to investigate the volatiles of as‐prepared C. militaris chicken soup. GC‐MS and GC ×GC‐TOF MS analysis indicated that contents and kinds of the main compounds especially aldehydes and esters which have fatty and sweet aroma in C. militaris chicken soup were increased after enzymolysis process. GC‐IMS results demonstrated that some volatile substances in chicken soup disappeared with the addition of C. militaris and concentrations of some volatile substances were increased after enzymolysis process. Enzymolysis pretreatment was confirmed to be an effective way to enhance the soluble protein dissolution rate and volatile flavour compounds of C. militaris chicken soup.
Quality improvement of Cordyceps militaris chicken soup by enzymolysis pretreatment.
•A new GC × GC–olfactometry–mass spectrometry system was used for soy sauce analysis.•All soy sauce samples had 55 odor-active compounds common among them.•Flavor dilution factors were used to ...evaluate the odor profile of the samples.•Soy sauce odor characteristics are affected by the balance of six odor attributes.
Activity of odor compounds of soy sauces has not been fully determined so far. Herein, a new switchable GC/GC × GC–olfactometry–mass spectrometry system for simultaneous GC × GC–MS analysis and sniffing of each odor-active substance through a single injection was used for the aroma extract dilution analysis of five regular high-salt liquid-state soy sauces (HLS). Methional, maltol, guaiacol, 4-ethylguaiacol, 2-acetylpyrrole, 2-acetylfuran, 2-phenylethanol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone showed high flavor dilution (FD) factors. The FD factors of all odor-active compounds in different odor attributes were summed up (score) to evaluate the odor characteristics of the samples. Cooked potato-like odor was the most important characteristic. The difference in the odor characteristics were mainly reflected in the balance of caramel-like/sweet, roasted/roasted nut-like, spicy/burnt, and unpleasant odor intensity; the fruity odor intensity was the weakest. This study will provide a better understanding of the odor characteristics and key odor-active compounds in Chinese regular commercial HLS.
•The application, potential, and limitations of GC × GC in forensic science were reviewed.•Only a limited number of publications were found using GC × GC for forensic investigations.•GC × GC data ...treatment and analysis for forensic comparison were described in detail.•Application of chemometric methods on GC × GC data for forensic comparison was reviewed.
In this study, the application of comprehensive two-dimensional (2D) gas chromatography (GC × GC) in forensic science is reviewed. The peer-reviewed publications on the forensic use of GC × GC and 2D gas chromatography with mass spectrometric detection (GC × GC–MS) have been studied in detail, not only to provide an overview, but also to analyze and understand the potential and limitations of this relatively novel analytical technique in forensic investigations. In order to make comprehensive GC × GC a powerful tool in forensic laboratories involved in chemical analysis, further developments are needed with respect to data analysis. Easy-to-use and “fit-for-forensic purpose” data analysis and chemometric tools will allow forensic analytical chemists to explore and compare the comprehensive data to provide solutions for relevant questions in criminal investigations.
Multidimensional gas chromatography in food analysis Nolvachai, Yada; Kulsing, Chadin; Marriott, Philip J.
TrAC, Trends in analytical chemistry (Regular ed.),
November 2017, 2017-11-00, Volume:
96
Journal Article
Peer reviewed
Open access
Multidimensional gas chromatography (MDGC) offers excellent separation efficiency that serves advanced characterisation of volatiles and semi-volatiles in food samples. An overview of recent data ...analysis, capabilities, and technologies in MDGC commencing from conventional heart-cut (MDGC), to its more recent comprehensive two-dimensional gas chromatography (GC×GC) variant is included. Selected applications are emphasised that include improved untargeted and target compound identification, fingerprinting and group type analysis, applied to food. Benefits to improved compound identification in MDGC by employing different hyphenation approaches are also emphasised. We conclude by highlighting recent advances and future trends, including three- and higher-dimensional GC with MS separation, on-line hyphenation with LC, and hybrid and multifunctional MDGC systems.
•Improved compound identification by using MDGC is emphasised.•Applications include fingerprinting and group type analysis approaches.•Benefits of MDGC hyphenated with FID, O, FTIR and MS for aromas is described.•Recent advances including >3 dimensions of GC and MS separation are highlighted.
•Discovery-based GC×GC–TOFMS analysis was applied to acid altered diesel fuel.•The aromatic species in the fuels were the most affected by the alteration.•The degree of removal followed reactivity to ...electrophilic aromatic sulfonation.•Null distribution analysis was applied to control the false discovery rate.•107 chemical features distinguished the acid altered diesel fuels.
The illicit chemical alteration of petroleum fuels is of keen interest, particularly to regulatory agencies that set fuel specifications, or taxes/credits based on those specifications. One type of alteration is the reaction of diesel fuel with concentrated sulfuric acid. Such reactions are known to subtly alter the chemical composition of the fuel, particularly the aromatic species native to the fuel. Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC–TOFMS) is well suited for the analysis of diesel fuel, but may provide the analyst with an overwhelming amount of data, particularly in sample-class comparison experiments comprised of many samples. Tile-based Fisher-ratio (F-ratio) analysis reduces the abundance of data in a GC×GC–TOFMS experiment to only the peaks which significantly distinguish the unaltered and acid altered sample classes. Three samples of diesel fuel from differently branded filling stations were each altered to discover chemical features, i.e., analyte peaks, which were consistently changed by the acid reaction. Using different fuels prioritizes the discovery of features likely to be robust to the variation present between fuel samples and may consequently be useful in determining whether an unknown sample has been acid altered. The subsequent analysis confirmed that aromatic species are removed by the acid alteration, with the degree of removal consistent with predicted reactivity toward electrophilic aromatic sulfonation. Additionally, we observed that alkenes and alkynes were also removed from the fuel, and that sulfur dioxide or compounds that degrade to sulfur dioxide are generated by the acid alteration. In addition to applying the previously reported tile-based F-ratio method, this report also expands null distribution analysis to algorithmically determine an F-ratio threshold to confidently select only the features which are sufficiently class-distinguishing. When applied to the acid alteration of diesel fuel, the suggested per-hit F-ratio threshold was 12.4, which is predicted to maintain the false discovery rate (FDR) below 0.1%. Using this F-ratio threshold, 107 of the 3362 preliminary hits were deemed significantly changing due to the acid alteration, with the number of false positives estimated to be about 3. Validation of the F-ratio analysis was performed using an additional three fuels.
•A robust method for vacuum GC×GC-TOFMS was developed.•Run times were 2.7 times shorter using the vacuum method than a conventional method.•Vacuum GC×GC-TOFMS yielded a lower peak capacity than the ...conventional GC×GC-TOFMS.•Vacuum and convention GC×GC-TOFMS produced a similar number of peaks-per-minute.
The analysis of thermally labile and high-boiling point compounds by gas chromatography (GC) can be a challenge. One technique to overcome these challenges is low-pressure GC, which uses the vacuum produced from the mass spectrometer and wide-bore columns to elute compounds at significantly lower temperatures. While GC-MS is a powerful technique, comprehensive two-dimensional gas chromatography (GC × GC), allows for resolution of compounds that would typically coelute using GC. In this study, a pesticide standard mixture (8270 MegaMix Standard) was analyzed using a conventional GC × GC-TOFMS configuration (0.25 mm inner diameter (i.d.) to a 0.18 mm i.d. column) and low-pressure GC × GC-TOFMS configuration (0.53 mm i.d. to a 0.53 mm i.d. column). Elution temperatures, sensitivity, and peak capacity were investigated for both configurations. Compounds eluted an average of 30 °C less on the low-pressure GC × GC-TOFMS configuration compared to the conventional GC × GC-TOFMS configuration. Moreover, the compounds were separated in ∼13 min on the low-pressure GC × GC-TOFMS as opposed to 33 min for conventional GC × GC-TOFMS. However, due to the wide-bore columns and faster runtimes the low-pressure GC × GC-TOFMS had a lower, β corrected 2D peak capacity, nc,β,2D, of 1260 while the conventional GC × GC-TOFMS was 3588. Interestingly, both configurations yielded a similar peak capacity production of 93 peaks/min and 107 peaks/min for low-pressure and conventional GC × GC-TOFMS, respectively. A “real world” sample of diesel fuel was tested on the low-pressure and conventional GC × GC-TOFMS configurations and similar results were obtained compared to the pesticide standard mix except the peak capacity production of the low-pressure GC × GC-TOFMS configuration was higher than that of the conventional GC × GC-TOFMS method.
•An ASE-GC×GC–TOF/MS multiresidue method was set up for PAH analysis in food.•GC–MS/8O enabled a robust determination of odour zones.•Heart-cutting GC–GC–MS/O resolved the remaining coelutions of key ...odorants.•PAHs and odour-active compounds were investigated in cooked meat.
The assessment of the dual impact of heating treatments on food safety and aroma is a major issue for the food sector. The aim of the present study was to demonstrate the relevance of multidimensional GC techniques, olfactometry and mass spectrometry for the parallel determination of process-induced toxicants and odorants in food starting with cooked meat as a food model. PAHs were analyzed by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry after extraction by accelerated solvent extraction (ASE-GC×GC–TOF/MS). Odour-active compounds were determined by dynamic headspace–GC hyphenated with eightbooth olfactometry and mass spectrometry (DH–GC–MS/8O) and DH-heart-cutting multidimensional GC hyphenated with olfactometry and mass spectrometry (DH–GC–GC–MS/O). For PAH determination, the GC×GC conditions consisted of a combination of a primary non-polar BPX-5 column and a secondary polar BPX-50 column, and a modulation period of 5s. In terms of linearity (R2 ranging from 0.985 to 0.997), recovery rate (84–111%) and limit of detection (5–65ng/kg of cooked meat), the ASE-GC×GC–TOF/MS method was found consistent with the multiresidue determination of 16 PAHs including benzoapyrene in cooked meat. For aroma compounds, DH–GC–MS/8O and DH–GC–MS/O revealed 53 major meat odour-active compounds. A customized heart-cutting GC–GC–MS/O enabled the coeluting odour zones with high odour-activity to be resolved and revealed 15 additional odour-active compounds. Finally, these developments of multidimensional approaches were used to investigate the balance between 16 PAHs and 68 odour-active compounds generated with different cooking techniques.
•The aroma compounds in Hanyuan Zanthoxylum bungeanum were identified by GC × GC-O-MS.•72 volatile compounds were identified by GC-O-MS, of which 28 were aroma-active.•116 volatile compounds were ...identified by GC × GC-O-MS, 43 of which were aroma-active.•23 important aroma-active compounds with FD ≥ 27 were identified by AEDA.•Compounds were quantified by external standard curves and OAV.
The present study sought to characterize the composition of volatile aroma compounds and key aroma-active compounds of dried Hanyuan Zanthoxylum bungeanum. The volatile aroma compounds were analyzed by the solid-phase microextraction (SPME) combined with gas chromatography–olfactometry-mass spectrometry (GC-O-MS) and two-dimensional comprehensive gas chromatography–olfactometry-mass spectrometry (GC × GC-O-MS). The key aroma-active compounds were analyzed by the aroma extract dilution analysis and odor activity value. A total of 72 volatile compounds were identified by GC-O-MS, of which 28 were aroma-active. Meanwhile, 116 volatile compounds were identified by GC × GC-O-MS, of which 43 were aroma-active. These results revealed that myrcene, (+)-limonene, (E)-β-ocimene, β-cubebene, Germacrene D, cineole, linalool, and linalyl acetate were the key aroma-active compounds of dried Hanyuan Zanthoxylum bungeanum.
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