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This study investigated the effect of heat treatments on the pungency and aroma profiles of a spice oleoresin blend, and the emulsion stability with different surfactants, encapsulating agents, and homogenization mechanisms. Total pungency increased with heat until 120 °C and drastically reduced at 150 °C. Thermal processing induced aroma release, and 46 compounds were identified at 90 °C, predominantly comprising sesquiterpenes. Tween 80 dispersed the highest oleoresin mass (6.21 ± 0.31 mg/mL) and reported the maximum emulsion stability index. The oleoresin percentage significantly influenced the emulsion stability, with 1% oleoresin producing the most stable emulsion. High-pressure homogenization applied on gum Arabic resulted in a greater encapsulation efficiency, exceeding 86%, and the lowest creaming index (4.70 ± 0.06%), while Hi-Cap 100 produced the best flow properties. The findings provide insights into incorporating lipophilic spice oleoresin blends in aqueous food systems and understanding the release of flavor compounds during thermal food processing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Membrane-based enantioselective separation is a promising method for chiral resolution due to its low cost and high efficiency. However, scalable fabrication of chiral separation membranes displaying both high enantioselectivity and high flux of enantiomers is still a challenge. Here, the authors report the preparation of homochiral porous organic cage (Covalent cage 3 (CC3)-R)-based enantioselective thin-film-composite membranes using polyamide (PA) as the matrix, where fully organic and solvent-processable cage crystals have good compatibility with the polymer scaffold. The hierarchical CC3-R channels consist of chiral selective windows and inner cavities, leading to favorable chiral resolution and permeation of enantiomers; the CC3-R/PA composite membranes display an enantiomeric excess of 95.2% for R-(+)-limonene over S-(-)-limonene and a high flux of 99.9 mg h -1 m -2 . This work sheds light on the use of homochiral porous organic cages for preparing enantioselective membranes and demonstrates a new route for the development of next-generation chiral separation membranes., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Since hop secondary metabolites have a direct correlation with the quality of beer and other hop-based beverages, and the volatile fraction of hop has a complex composition, requiring effective separation, here we explore the application of headspace solid-phase microextraction as a sample preparation method, coupled with comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC-MS) analysis. The methodology involved the use of a DVB/PDMS fibre with 500 mg of hop cone powder, extracted for 40 min at 50 °C, for both GC-MS and GC×GC-MS. The varieties Azacca, Cascade, Enigma, Loral, and Zappa were studied comprehensively. The results demonstrate that GC×GC-MS increases the number of peaks by over 300% compared to classical GC-MS. Overall, 137 compounds were identified or tentatively identified and categorised into 10 classes, representing between 87.6% and 96.9% of the total peak area. The composition revealed the highest concentration of sesquiterpene hydrocarbons for Enigma, whilst Zappa showed a relatively significant concentration of monoterpene hydrocarbons. Principal component analysis for all compounds and classes, along with hierarchical cluster analysis, indicated similarities between Zappa and Cascade, and Azacca and Loral. In conclusion, this method presents an optimistic advancement in hop metabolite studies with a simple and established sample preparation procedure in combination with an effective separation technique.

This study aims to assess and qualitatively compare the visual presentation of chromatographic data from the isomerisation of natural pyrethrins - a group of pesticides derived from Chrysanthemum flowers - using one-dimensional gas chromatography (1DGC) and comprehensive two-dimensional gas chromatography (GC×GC). Molecular structural changes, such as thermal isomerisation in this case, occur during gas chromatography injection and separation, to provide characteristic patterns which may not be routinely recognised on the 1D chromatogram. To demonstrate the influence of analytical method parameters on isomerisation processes, variations in oven temperature (isothermal vs. temperature programmed analysis), inlet mode (split vs. splitless), inlet temperature, and carrier gas flow rate were investigated. Increasing oven temperature was the most significant factor affecting isomerisation. Splitless injection mode and increasing inlet temperature promoted isopyrethrin formation, while the effect of inlet temperature appeared minimal with a split injection technique, most likely due to the short residence time in the inlet. Increased carrier gas flow rates in a temperature programmed analysis reduced retention time and minimised isomerisation. The unique presentation of isopyrethrin peaks on a GC×GC contour plot allows for facile recognition of isomerisation especially at low concentrations, simplifies chromatogram interpretation, and aids in analyte identification. It also confirms that the isomerisation process is irreversible since the pyrethrin I and II compounds are absent throughout the bridge formation. These benefits support the use of GC×GC over 1DGC to study isomerisation. Additionally, due to limited data in the literature, Kováts retention indices and linear retention indices of the natural pyrethrins, including isopyrethrins, were experimentally determined on four columns: DB-5 ms UI, Rxi-17Sil MS, SLB-IL60i, and SLB-IL111i., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier B.V. All rights reserved.)

The value of the concept of retention indices (RI) to the practice of gas chromatography (GC) is highlighted, where the RI of a compound is one component of the strategy to identify the compound. The widespread reliance on GC and then on mass spectrometry for 'identification', may result in inadequate confirmation of molecular identity. However, RI do provide a useful tentative indication of the possible molecule(s). Thus, the RI value is a useful first measure of the molecule identity, and shown here to be valuable provided limitations are recognised. An author has a responsibility to correctly calculate the index and then use the values for (tentative) identification. Tables of reference RI values are useful in this respect, but finding an 'exact match' RI value does not confirm the identity. Hence, it is necessary to understand how the RI value may be incorrectly used in this respect. The reviewer of written research is charged with ensuring the index values are applied in a rigorous manner. Selected case studies from our own work, support the care that must be exercised when reporting RI values. In terms of advanced GC operations, mention is made of multidimensional gas chromatography and comprehensive two-dimensional gas chromatography to acquire RI values on both the first and second columns in the two-column separation experiment., Competing Interests: Declaration of Competing Interest The authors declare that they have no competing interests in this submission. Philip Marriott On behalf of the authors, (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

The preferences of consumers for different flavours and aromas in wine are varied and may be explained by inherent factors such as cultural background, wine education and personal taste of the wine consumer. Wine flavour, as perceived in the mouth, includes aroma compounds released through the retronasal pathway, which are shaped by interactions with saliva. Saliva and wine interactions could provide an explanation as to why wine tasters express different preferences for wine. To test this hypothesis, 13 Western and 13 Chinese experienced wine tasters were recruited. Sensory evaluation was performed in formal surroundings to acquire free description-based and perceived sensory intensity data using the Pivot ® Profile and continuous scale assessment, respectively. Participants' saliva samples were collected before the sensory evaluation and spiked into a wine sample to investigate the impact on the wine's volatile release using comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS). Saliva samples were subjected to enzyme activity assays and protein composition profiling by Tandem Mass Tag (TMT) quantitative proteomics. The wine tasters showed differences in wine flavour perception, which was supported by the difference in wine volatile release resulting from the addition of saliva. The two groups of participants did not have significant differences in total salivary protein concentrations or the amounts of esterase and α-amylase. However, statistically significant variations in the concentrations of specific proteins (proline-rich proteins (PRPs) and lipocalin-1 (LCN-1); p < 0.01) were found between the two groups. Significant correlations between perceived intensities of wine attributes and concentrations of PRPs and LCN-1 were observed. These results indicate that the composition of proteins in saliva is a factor that influences wine perception and preference. Our results provide a biochemical basis for understanding preference for food based on interactions between aroma compounds and salivary proteins and could be used to suggest foods or beverages to particular cultural groups., (© 2023. Springer Nature Limited.)

Candida antarctica lipase A (CALA) was applied for the chemo-selective enzymatic transesterification of terpene and phenyl alcohols in 35 different essential oil samples. Comprehensive two-dimensional gas chromatography with mass spectrometry (GC×GC‒MS) analysis enabled the separation and tentative identification of a cohort of 125 compounds, allowing the instant visualisation of the reaction process changes, amid the complex chemical background of the samples. The results indicate that 42 out of 79 alcohols so-identified were fully or partially esterified within 48 h of reaction, with primary alcohols being the substrates of preference of the enzyme (90-100% conversion), followed by secondary alcohols (mostly ~ 80-100% conversion). No significant conversion of tertiary alcohols and phenols was observed using the tested conditions. Overall, the enzyme's performance was consistent for primary alcohol substrates identified in multiple samples of different compositions. The observed selectivity, efficiency, robustness, scalability (enzyme/substrate working concentration ratio > 1:160), potential reusability, mild reaction conditions, and other factors make this process a greener and more sustainable alternative for industry applications, particularly for the manufacture of novel flavours and fragrances., (© 2023. The Author(s).)

A multiloop splitter-based non-cryogenic artificial trapping (M-SNAT) modulation technique was established, which applied the first ( 1 D) nonpolar and the second ( 2 D) polar columns, deactivated fused silica (DFS) columns, a microfluidic Deans switch (DS), and splitters located between the 1 D column outlet and the DS. The splitters were connected into multiple loops with a progressively doubled perimeter of the next loop. This enabled a duplex splitting mechanism within each loop consisting of splitting of analyte pulses, the pulse delay, and their combination which led to equally split peaks of the same analytes with the number of split peaks ( n split ) equal to 2 m ( m = number of loops). This system resulted in local profiles of artificially split-and-trapped analytes prior to their selective transfers onto the 2 D column by means of periodic multiple heart-cuts (H/C). The developed SNAT approach can be successful, providing that the ratio of modulation period to sampling time ( P M / t samp ) is equal to n split . The approach with n split = 16 was further developed into a single device platform and applied for the modulation of a wide range of compounds in waste tire pyrolysis samples with the RSD of ≤0.01 and <10% for the one-dimensional modulated peak times and peak areas, respectively ( n = 50). The method enabled an artificial modulation mechanism without cryogen consumption and enhanced the 2 D peak capacity ( 2 n c ) and 2 D separation by use of a longer 2 D column.

Over the last decades, comprehensive two-dimensional gas chromatography (GC×GC) has emerged as a significant separation tool for high-resolution analysis of disease-associated metabolites and pharmaceutically relevant molecules. This review highlights recent advances of GC×GC with different detection modalities for drug discovery and analysis, which ideally improve the screening and identification of disease biomarkers, as well as monitoring of therapeutic responses to treatment in complex biological matrixes. Selected recent GC×GC applications that focus on such biomarkers and metabolite profiling of the effects of drug administration are covered. In particular, the technical overview of recent GC×GC implementation with hyphenation to the key mass spectrometry (MS) technologies that provide the benefit of enhanced separation dimension analysis with MS domain differentiation is discussed. We conclude by highlighting the challenges in GC×GC for drug discovery and development with perspectives on future trends.

Naphthenic acids (NAs) are naturally occurring organic acids in petroleum and are found in waste waters generated during oil production (produced water, PW). Profiling this class of compounds is important due to flow assurance during oil exploration. Compositional analysis of PW is also relevant for waste treatment to reduce negative impacts on the environment. Here, comprehensive two-dimensional gas chromatography coupled with high-resolution mass spectrometry (GC×GC-HRMS) was applied as an ideal platform for qualitative analysis of NAs by combining the high peak capacity of the composite system with automated scripts for group-type identification based on accurate mass measurements and fragmentation patterns. To achieve high-throughput profiling of NAs in PW samples, direct-immersion solid phase microextraction (DI-SPME) was selected for extraction, derivatization and preconcentration. A fully automated DI-SPME method was developed to combine extraction, fiber rinsing and drying, and on-fiber derivatization with N-methyl-N‑tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA). Data processing was based on filtering scripts using the Computer Language for Identifying Chemicals (CLIC). The method successfully identified up to 94 NAs comprising carbon numbers between 6 and 18 and hydrogen deficiency values ranging from 0 to -4. The proposed method demonstrated wider extraction coverage compared to traditional liquid-liquid extraction (LLE) - a critical factor for petroleomic investigations. The method developed also enabled quantitative analysis, exhibiting detection limits of 0.5 ng L -1 and relative standard deviation (RSD) at a concentration of NAs of 30 µg L -1 ranging from 4.5 to 25.0%., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest. This article does not contain any studies with human participants or animals performed by any of the authors., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chiral separation membranes have shown great potential for the efficient separation of racemic mixtures into enantiopure components for many applications, such as in the food and pharmaceutical industries; however, scalable fabrication of membranes with both high enantioselectivity and flux remains a challenge. Herein, enantiopure S-poly(2,4-dimethyl-2-oxazoline) (S-PdMeOx) macromonomers were synthesized and used to prepare a new type of enantioselective membrane consisting of a chiral S-PdMeOx network scaffolded by graphene oxide (GO) nanosheets. The S-PdMeOx-based membrane showed a near-quantitative enantiomeric excess (ee) (98.3±1.7 %) of S-(-)-limonene over R-(+)-limonene and a flux of 0.32 mmol m -2  h -1 . This work demonstrates the potential of homochiral poly(2,4-disubstituted-2-oxazoline)s in chiral discrimination and provides a new route to the development of highly efficient enantioselective membranes using synthetic homochiral polymer networks., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The performance of different enzymes towards the bioprocessing of aroma-related compounds was investigated and a strategy based on GC-FID analysis was developed to facilitate assessment of the stages of characterisation, screening and optimisation, including chiral ratio determination. Characterisation included activity assays (UV-Vis and GC-FID), protein quantification (NanoDrop spectrophotometry) and molar mass estimation (SDS-PAGE electrophoresis). Screening experiments assessed different enzymes, substrates, solvents, acyl donors or mediators. Aroma-related substrates comprised terpene and phenolic compounds. The enzymes tested included the lipases CALA (Sigma-Aldrich), NZ-435, LZ-TLIM, NC-ADL, LZ-CALBL and the laccases NZ-51003 and DL-IIS (all from Novozymes). Among those, NZ-435 and NZ-51003 had the highest activities in the characterisation stage and, along with CALA, achieved conversions above 70% for citronellol (lipases) or 50% for eugenol (laccases) at the screening stage. The lipases had preference for the primary alcohol and laccases for phenolic compounds, among the tested substrates. The transesterification reaction between the lipase CALA and the standards mixture (citronellol, menthol, linalool) was used to demonstrate the optimisation stage, where the best levels of temperature, enzyme and acyl donor concentrations were investigated. Optimum conditions were found to be 37-40 °C, 3-4 mg/mL of enzyme and 58-60% (v/v) vinyl acetate. Additional confirmation experiments using the same terpene standards mixture and citronella oil sample, gave a conversion of > 95% for citronellol after 1 h (for both, standards mixture and sample), and 20% or 74% for menthol after 1 h or 24 h, respectively. None of the tested enzymes demonstrated significant enantioselectivity under the tested conditions. The GC-FID approach demonstrated here was suitable to determine the reaction profiles and chiral ratio variations for biocatalysed reactions with aroma compounds in low complexity samples. Advanced separations will be applied to more complex samples in the future., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The detection of human-derived metabolites as potential diagnostic biomarkers of genetic disorders, metabolic diseases, systemic diseases, and infectious diseases has been much studied in recent years, especially as technical capabilities improve, and statistical procedures are increasingly able to tease critical chemical attributes from complex data sets. Given the complex distribution of human biological matrices, the characterization and/or identification of these chemical entities is technically challenging, and is often confounded by incomplete chromatographic resolution or insufficient discriminatory power of the mass spectrometry (MS) domain. Recently, comprehensive two-dimensional gas chromatography (GC×GC) has evolved into a mature higher separation order technique that offers unprecedented resolving power, which in turn can greatly advantage clinical metabolomics studies via the expansion of metabolite coverage. In this contribution, the current state of knowledge in the development of GC×GC coupled to MS as a high-resolution bioanalytical technique for the analysis of clinical metabolites is reviewed. Selected recent applications (years 2012 to 2021) that emphasize improved GC×GC-MS strategies for clinical human metabolites' detection, identification, and quantitative analysis are described. In addition, we share our perspectives on current challenges and potential future directions of GC×GC in clinical applications.

This study evaluates the volatile metabolic constituents and anticancer potential of essential oils distilled from the rhizomes of four Malaysian Zingiber officinale Roscoe (Zingiberaceae family) varieties (Bentong (BE), Cameron Highlands (CH), Sabah (SA), and Bara (BA)). The ginger essential oils were analyzed by gas chromatography coupled with quadrupole mass spectrometry (GC qMS). A total of 58 secondary compounds were tentatively identified, representing 82.6-87.4% of the total ion count. These metabolites comprise mainly of monoterpene hydrocarbons (19.7-25.5%), oxygenated monoterpenes (23.6-33.7%), sesquiterpene hydrocarbons (21.3-35.6%), oxygenated sesquiterpenes (1.5-3.9%), and other minor classes of compounds (0.7-2.7%). Principal component analysis (PCA) enabled differentiation of the analyzed ginger essential oils according to their varieties, with respect to their metabolites and relative quantities. The antiproliferative activity against the HeLa cervical cancer cell line was investigated via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The oils were found to exhibit strong antiproliferative activities with IC 50 values of 23.8, 35.3, 41.3, and 42.5 μg/mL for BA, BE, SA, and CH, respectively. These findings suggest that the differences among the secondary metabolites and their abundance in different varieties of Z. officinale essential oils appear to be related to their antiproliferative potential. The strong antiproliferative effects of these oils signified their potential in the prevention and chemotherapy of cervical carcinoma treatment.

The definition of a chromatographic analysis speed based simply on analysis time is an outdated concept to define conventional chromatography, fast chromatography, and emerging high-resolution techniques such as comprehensive two-dimensional and comprehensive three-dimensional gas chromatography. Here, the metric average theoretical peak time (ATPT) is proposed for separation speed, considering conventional and multidimensional separations. ATPT can be defined as the time (in ms per peak) needed to elute a theoretical peak in a chromatographic system. Using this metric, it is possible to define ranges, proposed for a normal speed (ATPT higher than 4000 ms/peak), high speed (ATPT range from 600 to 4000 ms/peak), very high speed (ATPT range from 200 to 600 ms/peak), hyper speed (ATPT range from 3.3 to 200 ms/peak) and ultra high speed chromatography (ATPT lower than 3.3 ms/peak), that combines time and efficiency metrics. This metric was applied in several contexts to demonstrate its robustness to evaluate chromatographic separations for different techniques and analytical conditions. Applications also demonstrate the advantages of the use of ATPT as a method development metric tool., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

An improved strategy for compound identification incorporating gas chromatography hyphenated with Fourier transform infrared spectroscopy and mass spectroscopy (GC-FTIR/MS) is reported. (Over)reliance on MS may lead either to ambiguous identity or to incorrect identification of a compound. However, the MS result is useful to provide a cohort of possible compounds. The IR result for each tentative compound match was then simulated using molecular modeling, to provide functional group and isomer differentiation information, and then compared with the experimental FTIR result, offering identification based on both MS and IR. Several basis sets were evaluated for IR simulations; Def2-TZVPP was a suitable basis set and correlated well with experimental data. The approach was applied to industrial applications, confirming the isomers of 2,3-bis(thiosulfanyl)-but-2-enedinitrile, bromination products of 1-bromo-2,3-dimethylbenzene, and autoxidative degradation of phenyl-di- tert -butylphosphine.

The volatile profile of raw beef contains vital information related to meat quality and freshness. This qualitative study examines the effect of packaging system on the formation and release of volatile organic compounds (VOCs) from raw beef over time, relative to the packaging best before date (BBD). The three packaging systems investigated were modified atmospheric packaging, vacuum packaging, and cling-wrapped packaging. Porterhouse steak samples with the same BBD were analysed from 3 days before to 3 days after the BBD. VOCs were detected via preconcentration using solid-phase microextraction combined with gas chromatography-accurate mass quadrupole time-of-flight mass spectrometry. In total, 35 different VOCs were tentatively identified. Interestingly, there was no clear relationship of the VOCs detected between the three packaging systems, with only carbon disulphide and acetoin, both known volatiles of beef, detected in all three. This is the first study to investigate the effects of commercial packaging systems on VOC formation; it provides an understanding of the relationship of VOCs to the BBD that is essential for the development of on-pack freshness and quality sensors.

Cryogenic methods - those that employ cryogenic fluids/gases but also other approaches to generate reduced temperature - are versatile, functional and relatively easily implemented as part of a total gas chromatographic method. The general utility of a cold region is almost invariably as a trapping or focussing step, to collect analyte into a sharp zone. The success in effectively trapping analyte depends on analyte volatility and the temperature of the cold region. Analytes collection into a sorbent phase supported by cryotrapping usually provide a greater capacity trapping for the sorption step. Stripping analyte from a sample into a cryogenic trap, with subsequent introduction to GC as in a purge-and-trap method, sample introduction into an injector with incorporation of a cooling zone, manipulation and management of chromatographic bands during chromatography elution such as employed in multidimensional gas chromatography, and focussing analyte just prior to the detector, all have the same goal of concentrating the band, reducing its dispersion, and maximising response. This review summarises various approaches that demonstrate how cryogenic methods have been incorporated into gas chromatographic analysis., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest in the research reported herein., (Copyright © 2021. Published by Elsevier B.V.)

In contrast to the well-known comprehensive two-dimensional gas chromatography (GC×GC) method, it is possible to define comprehensive multidimensional gas chromatography. 'Comprehensiveness' relates to analysis of the whole sample. Two-dimensional and multidimensional here refer to the use of at least two separation stages for analysis, however comprehensive 2DGC now appears to be reserved for the GC×GC method. This may be differentiated from comprehensive MDGC (CMDGC) simply by the analysis time assigned to the second ( 2 D) column, although there does not appear to be a specific definition that relates to this analysis time parameter. A number of different implementation protocols for comprehensive MDGC are described here, that may involve either a single, or multiple, injection(s). In all cases, independent retention must be achieved on each dimension to ensure the probability of enhanced separation. An original application of a crude oil sample is presented to illustrate development of the MDGC approach that incorporates two Deans switches (DS) and a cryogenic trapping approach, performed using a sequential heart-cut (H/C) event method incremented by 0.5 min for each injection; a total of 40 injections is used to analyse the total sample. The higher peak capacity and consequently greater resolution on the long 2 D column is illustrated, compared with that expected for conventional GC×GC, with tentative identification in order to classify chemical classes. Incorporating an approach to acquiring retention indices may be implemented, although its utility for petroleum hydrocarbons is limited. Structured groupings of different chemical classes, as exemplified by mono and diaromatics for the crude oil sample, were noted., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest with the present work., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A 'heart-cut' multidimensional gas chromatography‒mass spectrometry (H/C MDGC‒MS) method for separation and identification of triacylglycerols (TAGs) in extra virgin olive oil was developed. A GC configuration, comprising a non-polar first dimension ( 1 D) column (15 m length) and a mid-polarity second dimension ( 2 D) column (9 m length), was employed. Standard TAGs were used to test and demonstrate the H/C MDGC method, for identification of TAG components and to validate the method. Various chromatographic conditions such as column flow and temperature program were evaluated. The 1 D separation resulted in overlap of some standard TAG peaks. These overlapped 1 D regions of the standard TAGs were H/C to 2 D for further separation and resulted in clearly distinguished individual TAG component peaks. The 1 D separation of olive oil TAGs displayed three major peaks and four minor peaks. The application of the H/C MDGC method to olive oil TAGs resulted in the separation of each sampled 1 D region into two or more TAG peaks. TAG components in olive oil resolved on the 2 D column were identified based on characteristic mass fragment ions such as [M-RCO 2 ] + , [RCO+128] + , [RCO+74] + and RCO + and comparison of their mass spectra with that of the standard TAGs. Sixteen olive oil TAGs were identified by MS after 2 D separation. The repeatability of the H/C method was evaluated in terms of retention time shift and area response in the 2 D and found to be <0.02% and <8% RSD respectively., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A data interpretation and processing approach for improved compound identification and data presentation in comprehensive two-dimensional gas chromatography (GC×GC) is described. A footprint peak of a compound in 2D space can be represented by a centroid or peak apex, similar to the data-reduced histogram spectra used in mass spectrometry. The workflow was demonstrated on data from GC×GC-TOFMS. Peaks in a modulated chromatogram were initially detected by conventional chromatographic integration, followed by a curve-fitting approach, which interpolated high-precision, absolute retention times for all modulated peaks. First dimension retention time ( 1 t R ) was obtained by using an exponentially modified Gaussian (EMG) fitting model for near-Gaussian distributed subpeaks, polynomial fitting for highly asymmetrical peaks, and parabolic fitting for under-sampled peaks, which allows determination of a precise 1 t R , considering the dwell-time arising from modulation and 2 t R . Area summation of the modulated peaks belonging to the same compound was then performed to yield the total peak area. Each compound in the GC×GC-MS result was then represented by its position at the intersecting coordinates, ( 1 t R , 2 t R ), in the 2D separation plane, having a height of the same magnitude as the total component summed area. This results in a novel and uncluttered GC×GC output convention based on the scripted total ion chromatogram (TIC) data with precise 1 t R , 2 t R , and area. Comparison between the contour plots from the scripted and conventional TIC revealed improved data presentation, accompanied by an apparent enhanced resolution. The described approach was applied to the identification of 177 aroma compounds from peaches as indicators of fruit quality.

Approaches to simulate peak time and intensity profiles of compounds in comprehensive two dimensional gas chromatography (GC × GC) were developed, and which are demonstrated for separation of a mixture of saturated and unsaturated fatty acid methyl esters (FAME) using a range of column sets. The simulation of first and second dimension time ( 1 t R and 2 t R ) of FAME relies on use of a Gibbs energy additivity approach to correlate with the structures of FAME. First and second dimension peak standard deviations ( 1 σ and 2 σ) of the compounds were further calculated from the 1 t R and 2 t R data according to the plate height concept which provided good agreement between the predicted and experimental peak widths at half height in one dimension GC (1DGC) with an overall R 2 of 0.9628. The effect of 1 σ distortion caused by the modulation process was also taken into account in the peak width simulation where the simulated 1 σ data were rounded up to multiples of the scale of modulation period (P M ). Two dimension Gaussian equations were then used to generate GC × GC results (2D contour plots) from simulated 1 t R , 2 t R , 1 σ and 2 σ data for FAME separation on different column sets employing ionic liquid and conventional columns. Good overall correlations between experimental and simulated 1 t R and 2 t R were obtained with R 2 of 0.9951 and 0.9802, respectively, and the simulated 2D contour plots were an acceptable match with the experimental results., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Terpenes and their derivatives, terpenoids, are important biomarkers of grape quality as they contribute to flavor and aroma of grape and wine. The evolution of terpene and terpenoids throughout grapevine phenological development cycles is not well understood. The current study investigated the volatile profiles of free terpene and terpenoid of five widely grown Vitis vinifera L. cultivars (Shiraz, Cabernet Sauvignon, Riesling, Chardonnay and Pinot Gris), at different phenological stages from fruit-set to harvest. 17 Monoterpenoids, 3 norisoprenoid and 13 sesquiterpenoids were identified and quantified. Discriminant analysis revealed that for each grape cultivar, free terpene profiles at different E-L stages were distinctive. When integrating total sugar, total terpenes and the cumulated heat index, it could be found that flavor ripening was more consistent with sugar ripening in the warmer vintage 2016. Comparing the two red wine varieties, the overall development patterns of total monoterpenes, norisoprenoids and sesquiterpenes were similar., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Homochiral metal-organic framework (MOF) membranes have been recently reported for chiral separations. However, only a few high-quality homochiral polycrystalline MOF membranes have been fabricated due to the difficulty in crystallization of a chiral MOF layer without defects on porous substrates. Alternatively, mixed matrix membranes (MMMs), which combine potential advantages of MOFs and polymers, have been widely demonstrated for gas separation and water purification. Here we report novel homochiral MOF-polymer MMMs for efficient chiral separation. Homochirality was successfully incorporated into achiral MIL-53-NH 2 nanocrystals by post-synthetic modification with amino acids, such as l-histidine (l-His) and l-glutamic acid (l-Glu). The MIL-53-NH-l-His and MIL-53-NH-l-Glu nanocrystals were then embedded into polyethersulfone (PES) matrix to form homochiral MMMs, which exhibited excellent enantioselectivity for racemic 1-phenylethanol with the highest enantiomeric excess value up to 100 %. This work, as an example, demonstrates the feasibility of fabricating diverse large-scale homochiral MOF-based MMMs for chiral separation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study develops analytical approaches using comprehensive heart-cut multidimensional gas chromatography (H/C MDGC) to experimentally investigate effects of concentration and temperature on peak shapes and on kinetic analysis of E/Z isomerisation of oximes which undergo various extents of interconversion on 1 D and 2 D separation columns. Different stationary phase combinations were investigated. An SLB-IL76 1 D column results in good separation of the isomers but with negligible interconversion ( 1 D sep ). Precise targeted heart-cuts (H/C; 3-15 s windows) and cryogenic trapping of selected sections eluting from this 1 D column allows well controlled E/Z isomer ratios to be delivered to a 2 D poly(ethyleneglycol) (PEG) phase column. This phase catalyses oxime interconversion, with separation; this is termed 2 D inter . This column set describes a 1 D sep  ×  2 D inter arrangement. The interconversion forward rate constant (k 1 UE , calculated by using DCXplorer) was found to be independent of the %E isomer (i.e. first order kinetics); k 1 UE increased at higher temperature (increased Gibbs activation energies, ΔG app ). In addition, a long 1 D SLB-IL111 column gave oxime separation with interconversion ( 1 D inter ). Comprehensive multiple H/C of the zone performed on the 2 D PEG ( 2 D inter ) at 40, 60 and 80 °C resulted in a 2D presentation ( 1 D inter  ×  2 D inter ) with a unique rectangular display of interconversion from each H/C pulse with varied isomer concentration ratios. Data for k 1 UE from 1DGC analysis suggests underestimation of k 1 UE on 1 D inter SLB-IL111 from the 2D result. The k 1 UE value on 2 D inter PEG column is more reliably evaluated by summation of all the 2 D inter profiles rather than that obtained from the average value for the individual H/C pulses., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Five Vitis vinifera L. cultivars Shiraz, Cabernet Sauvignon, Riesling, Chardonnay and Pinot Gris at different E-L development stages were harvested in two experimental vintages. Temperature and rainfall data of the growing period were obtained from the Australian Government Bureau of Meteorology. Free terpene concentrations of all harvested grape samples were analysed using HS-SPME-GC-MS. One-way ANNOVA was performed to evaluate the significance of changes in terpene concentrations at different maturation stages. More analysis of the data is provided in "Free terpene evolution during the berry maturation of five Vitis vinifera L. cultivars" [1]., (© 2019 The Author(s).)

This study reports gas chromatography (GC) combined with Fourier transform infrared (FTIR) spectroscopy to investigate the elution profiles of individual oxime isomers undergoing characteristic interconversion (dynamic chromatography) in GC. The use of a light-pipe FTIR interface enables on-line acquisition of FTIR spectra, which in turn render unambiguous identification of the individual molecules. Here, acetaldehyde oxime and propionaldehyde oxime were chosen for comparison of elution behaviour under varying temperature and carrier flow velocities. The choice of selective responses (wavenumber selectivity), which were relatively stronger for each isomer, enabled display and retracing of the individual isomer over the chromatographic time scale and thus provided characteristic single isomer profiles. Chemometric data analysis using the multivariate curve resolution technique further confirmed this isomer elution profile. Simulation of the spectrum for each isomer allowed comparison with instrument-generated FTIR spectra to confirm the elution order of E and Z isomers. The effect of changing chromatographic parameters (temperature, flow) on interconversion rates and/or extents were studied and the corresponding change in FTIR spectrum intensity was noted. The GC-FID data acquired concurrently with GC-FTIR analyses ratified isomerisation chromatographic profiles.

Multidimensional approaches in gas chromatography have been established as potent tools to (almost) attain fully resolved analyses. Flavours and odours are important application fields for these techniques since they include complex matrices, and are of interest for both scientific study and to consumers. This article is a review of the main research studies in the above theme, discussing the achievements and challenges that demonstrate a maturing of analytical separation technology.

A novel dynamic approach is described to profile volatile organic compound (VOC) and semi-VOC (SVOC) emission during coffee roasting aimed at analysing components present in the roasting plume, and to monitor their evolution during the process. Two sorbents - coconut shell charcoal (CSC) and styrene-divinylbenzene resin (XAD-2) - were evaluated while collecting substances in four sequential time intervals (0-3, 3-6, 6-9 and 9-12 min). Extracted VOCs (<200 Da) and SVOCs were analysed by gas chromatography (GC), and comprehensive two-dimensional gas chromatography (GC × GC) with flame ionisation (FID) and time-of-flight mass spectrometry (TOFMS) detection. Results showed CSC extraction presented poor recovery of VOCs and SVOCs released during roasting. However, XAD-2 was able to collect both groups, including SVOCs of >400 Da. GC × GC resolved many co-eluting compounds observed in 1D GC and allowed chemical group type cluster analysis, revealing that many non-polar VOCs are observed within the 0-3 min interval, and that the release of polar and higher molar mass SVOCs were mostly found within the 3-6 min interval. These group-type cluster analyses offer a broad spectrum chemical profile of the released substances. It may also reveal detailed insights into the roast process evolution over time., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this work, a method for the analysis of benzoylurea insecticides, including hexaflumuron, flufenoxuron, lufenuron and chlorfluazuron, in tea samples by high-performance liquid chromatography with Fe 3 O 4 -hyperbranched polyester nanocomposite as the adsorbent for magnetic solid-phase extraction was developed. The magnetic nanocomposite was prepared and characterized by infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy. The as-prepared nanocomposite was used as a sorbent for the extraction and preconcentration of pesticide residues in tea samples. The extraction and desorption conditions, including mass ratios of raw materials, amount of sorbent, pH value, extraction time, and desorption time, were investigated. Under the final conditions chosen for the analysis, good linearity was obtained for all the tested compounds, with R 2 values of at least 0.9979. The limits of detection were determined in the range of 0.15-0.3 μg/L. The recovery obtained from the analysis of tea samples with various spiked concentrations was between 90.7 and 98.4%, with relative standard deviations (n = 4) lower than 4.1%. Furthermore, the present approach was successfully applied to the quantitative determination of residues of benzoylurea insecticides in real samples., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Sapucainha oil, which may be used to treat leprosy, comprises straight chain and cyclic fatty acids (FA), and triacylglycerols (TAG). The FA and TAG content of the oil sample was analysed using gas chromatography-electron ionisation mass spectrometry (GC-EIMS). FA analysis was performed after derivatisation to fatty acid methyl esters (FAME). For free FA and TAG analysis, the oil sample was dissolved in hexane and injected into a short, high-temperature column, for GC with MS analysis. Free FA and FAME were tentatively identified based on mass spectrum information of their molecular and fragment ions, as well as library matching. Overlapping TAG peaks were deconvoluted based on mass fingerprint data. The FA composition was utilised to predict possible TAG identities. FA residues of TAG were identified based on characteristic fragment ions, such as [M-RCO 2 ] + , [RCO+128] + , [RCO+74] + and RCO + where R is the aliphatic hydrocarbon chain. FAME analysis showed that the cyclic FA hydnocarpic (36.1%), chaulmoogric (26.5%) and gorlic (23.6%) acids were the major components. In addition, straight chain FA such as palmitic, palmitoleic, stearic, oleic and linoleic acids were detected. Palmitic, oleic, hydnocarpic, chaulmoogric and gorlic acids were also detected as free FA in the oil sample. Six groups of TAG peaks were eluted from GC at temperatures ≥330 °C. After deconvolution and mass spectrum analysis, each TAG peak group was revealed to comprise 2 to 5 co-eluted TAG molecules; >18 TAG were identified. These TAG consisted of a mix of both cyclic and straight chain FA, but were mostly derived from cyclic FA.

This study investigated the volatile phytochemical diversity of 30 samples obtained from experimental hybrid and commercial H. lupulus L. plants. Essential oils distilled from these samples were analysed by high resolution gas chromatography coupled with accurate mass time-of-flight mass spectrometry (GC-accTOFMS). A total of 58 secondary metabolites, mainly comprising 18 esters, 6 monoterpene hydrocarbons, 2 oxygenated monoterpenes, 20 sesquiterpene hydrocarbons, 7 oxygenated sesquiterpenes, and 4 ketones, were positively or tentatively identified. A total of 24 metabolites were detected in all samples, but commercial cultivars (selected for brewing performance) had fewer compounds identified compared to experimental genotypes. Chemometrics analyses enabled distinct differentiation of experimental hybrids from commercial cultivars, discussed in terms of the different classes of compounds present in different genotypes. Differences among the mono- and sesquiterpenoids, appear to be related to either: i) the genetic origin of the plants; or ii) the processes of bioaccumulation of the identified secondary metabolites., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Small bowel obstruction is a common surgical emergency, and is associated with high levels of morbidity and mortality across the world. The literature provides little information on the conservatively managed group. The aim of this study was to describe the burden of small bowel obstruction in the UK., Methods: This prospective cohort study was conducted in 131 acute hospitals in the UK between January and April 2017, delivered by trainee research collaboratives. Adult patients with a diagnosis of mechanical small bowel obstruction were included. The primary outcome was in-hospital mortality. Secondary outcomes included complications, unplanned intensive care admission and readmission within 30 days of discharge. Practice measures, including use of radiological investigations, water soluble contrast, operative and nutritional interventions, were collected., Results: Of 2341 patients identified, 693 (29·6 per cent) underwent immediate surgery (within 24 h of admission), 500 (21·4 per cent) had delayed surgery after initial conservative management, and 1148 (49·0 per cent) were managed non-operatively. The mortality rate was 6·6 per cent (6·4 per cent for non-operative management, 6·8 per cent for immediate surgery, 6·8 per cent for delayed surgery; P = 0·911). The major complication rate was 14·4 per cent overall, affecting 19·0 per cent in the immediate surgery, 23·6 per cent in the delayed surgery and 7·7 per cent in the non-operative management groups ( P < 0·001). Cox regression found hernia or malignant aetiology and malnutrition to be associated with higher rates of death. Malignant aetiology, operative intervention, acute kidney injury and malnutrition were associated with increased risk of major complication., Conclusion: Small bowel obstruction represents a significant healthcare burden. Patient-level factors such as timing of surgery, acute kidney injury and nutritional status are factors that might be modified to improve outcomes.

A simple sample preparation method based on a modified liquid-phase extraction approach to extract selected pharmaceuticals and personal care products from freshwater organisms is described. Extracted samples were analysed using liquid chromatography with Q-Exactive plus hybrid quadrupole Orbitrap mass spectrometry, using 2.6 μm C18 media. A 0.1% v/v acetic acid/acetonitrile mobile phase was applied over a 20 min gradient. Method detection limits in full scan mode were ca. 0.04-2.38 ng of analyte per g of sample. Linearity ranged from 0.9750 to 0.9996 over the calibration range of 0.01-100 μg/L; MS mass accuracy was <2 ppm for most analytes. This method was applied to quantify six pharmaceuticals and personal care products in seven invertebrate samples. For tandem mass spectrometry analysis, selection of precursor ions was performed for each pharmaceutical, with Mass Frontier software illustrating the fragmentation mechanism. Effects of collision energy on intensities of ions was further investigated. The tandem mass spectrometry condition resulting in the highest signal of respective selected product ion was selected to confirm each pharmaceutical, which was initially observed in the full scan mode. Results indicate that pharmaceuticals and personal care products found to be present in water-ways, may be incorporated into organisms that live in the environment of affected water streams., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cafestol and kahweol (C&K), two coffee diterpene alcohols with structural similarity which exhibit anticarcinogenic effects, were isolated from green coffee Arabica beans, followed by their lipase-catalysed esterification and purification by preparative high-performance liquid chromatography (HPLC). The isolation and enzymatic synthesis parameters of C&K esters were studied, with the latter optimised by a Central Composite Design; both procedures were monitored by gas chromatography. Scale up and improved isolation conditions resulted in 1.29 g of C&K, with 98% purity from 300 g of green Arabica beans. The highest C&K ester yields were observed using an alcohol:fatty acid molar ratio of 1:5, 73.3 mg mL -1 of CAL-B enzyme, 70 °C and 240 rpm for 3 days in toluene, leading to 85-88% conversion among a variety of tested C&K esters, including n-C 14:0 -C 20:0 , C 18:1 , C 18:2 and C 18:3 ., (Copyright © 2018. Published by Elsevier Ltd.)

Safflower is an important industrial oil seed and bioenergy crop in semi-arid subtropical regions due to its potential to grow on marginal land and having good percentage of seed oil contents which is an important parameter for biofuel production. However, it is an ignored crop in Pakistan. In order to improve the crop productivity and reduce the use of agrochemicals for sustainable biodiesel feedstock production, an experiment was conducted for two years to improve the fatty acid composition and oil quality of Carthamus tinctorius L. (safflower) by the inoculation of Azospirillum and Azotobacter alone as well as in combined application with nitrogen and phosphate (NP) fertilizers on cultivars Thori and Saif-32 under field conditions. Separation and quantification of fatty acids were done on precise comprehensive two-dimensional gas chromatography (GC×GC). The results showed that fatty acid profile specifically monounsaturated fatty acids i-e oleic acid (C18:1) was significantly improved by Azospirillum supplemented with the quarter dose of NP fertilizers (SPQ) with concomitant decrease in polyunsaturated fatty acids by the respective treatment. Oil quality attributes such as acid value, saponification number, iodine value, refractive index and free fatty acid contents were reduced by the application of Azotobacter and Azospirillum in combination with half and quarter doses of NP fertilizers treatments (BTH, SPH, BTQ and SPQ). The reduction in these variables is positively linked with improved biodiesel yield and quality. It can be concluded that application of Azospirillum and Azotobacter not only reduced the use of NP fertilizers up to 50%-75% but also improved the oil quality in order to obtain environment friendly, sustainable and green fuel., Competing Interests: The authors have declared that no competing interests exist.

In the past 15+ years, gas chromatography (GC) has undergone a renaissance in its implementation on the basis of the "disruptive" technology of comprehensive two-dimensional gas chromatography (GC×GC). With a foundation based upon a two-column GC separation approach, GC×GC significantly alters the classical multidimensional gas chromatography (MDGC) method by employing very fast separation on a second dimension ( 2 D) after a conventional one-dimensional (i.e., single column; 1D) column separation. This allows the experimentalist to apply the advantages of multidimensionality to the total sample rather than to just discrete zones of the 1D separation that characterizes MDGC. This requires a new "language" to describe GC×GC separations, applied to the first dimension ( 1 D) and 2 D, and consideration of the modulation processes that define the transfer of analyte from the 1 D to the 2 D. The present review is based on the FACS Foundation lectureship of the author given at the 17th Asian Chemical Congress of the Federation of Asian Chemical Societies (FACS). The award lecture and this manuscript is based on material deriving largely from research in the area of MDGC and GC×GC separations of the author., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)