Display omitted
•Classification, odor description, and chemistry of rice VACs have described.•Important information on aroma research of rice and its products have focused.•SPME is mostly used as a ...recent method for extracting rice VACs.•GC–MS is frequently used to identify and characterize rice VACs.
The aroma in rice and its products is one of the important quality characteristics. It is contributed by more than 500 different volatile compounds and the extraction and quantification of aroma compounds are equally essential, determining the threshold of aroma. Till date,a complete review of the aromatic consideration of rice is lacking in the literature. Therefore, thepresent paper is prepared with the aim of summarizing the data and other significant informationin respect of the aroma characteristics of different types of rice and rice productsfrom the early 1980s to 2019.This review discusses all the studies on extraction, isolation, and characterization of volatile aroma compounds (VACs) done in different types of rice and their products which will further help researchers to continue their work on the lacking aspects of rice aroma. A special focus has been given to the 2-AP compound which signified the difference between aromatic and non-aromatic rice cultivars.
► We developed a simple and fast method for extraction of PAHs from smoked fish. ► Microwave assisted extraction (MAE) was used to release of PAHs from smoked fish. ► DLLME was used for quick ...pre-concentration of PAHs from the hydrolyzing solvent. ► Final separation and quantification was performed by GC–MS. ► The figures of merit for 16 PAHs in smoked fish using the MAE–DLLME were excellent.
A simple and efficient method was developed using microwave-assisted extraction (MAE) and dispersive liquid–liquid microextraction (DLLME) coupled with gas chromatography–mass spectrometry (GC–MS) for the extraction and quantification of 16 polycyclic aromatic hydrocarbons (PAHs) in smoked fish. Benzoapyrene, chrysene and pyrene were employed as model compounds and spiked to smoked fish to assess the extraction procedure. Several parameters, including the nature and volume of hydrolysis, extracting and disperser solvents, microwave time and pH, were optimized. In the optimum condition for MAE, 1g of fish sample was extracted in 12mL KOH (2M) and ethanol with a 50:50 ratio in a closed-vessel system. For DLLME, 500μL of acetone (disperser solvent) containing 100μL of ethylene tetrachloride (extraction solvent) was rapidly injected by syringe into 12mL of the sample extract solution (previously adjusted to pH 6.5), thereby forming a cloudy solution. Phase separation was performed by centrifugation and a volume of 1.5μL of the sedimented phase was analyzed by GC–MS in select ion monitoring (SIM) mode. Satisfactory results were achieved when this method was applied to analyze the PAHs in smoked fish samples. The MAE–DLLME method coupled with GC–MS provided excellent enrichment factors (in the range of 244–373 for 16 PAHs) and good repeatability (with a relative standard deviation between 2.8 and 9%) for spiked smoked fish. The calibration graphs were linear in the range of 1–200ngg−1, with the square of the correlation coefficient (R2)>0.981 and detection limits between 0.11 and 0.43ngg−1. The recoveries of those compounds in smoked fish were from 82.1% to 105.5%. A comparison of this method with previous methods demonstrated that the proposed method is an accurate, rapid and reliable sample-pretreatment method that gives very good enrichment factors and detection limits for extracting and determining PAHs from smoked fish.
► A method for analysis 30 pesticide residues in vegetables and fruits was developed. ► The original QuEChERS method was employed. ► The extract was cleaned up by r-DSPE using mixture of MWCNTs, ...instead of PSA. ► Recoveries ranged from 71% to 110% with RSDs lower than 15%. ► The method was successfully applied to the real samples.
A multi-residue method based on modified QuEChERS sample preparation with multi-walled carbon nanotubes (MWCNTs) as reversed-dispersive solid phase extraction (r-DSPE) material and gas chromatography–mass spectrometry determination by selected ion monitoring (GC/MS-SIM) mode was validated on 30 representative pesticides residues in vegetables and fruits. The acetonitrile-based QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation technique was used to obtain the extracts, and the further cleanup was carried out by applying r-DSPE. It was found that the amount of MWCNTs influenced the cleanup performance and the recoveries. The optimal amount of 10mg MWCNTs was suitable for cleaning up all selected matrices, as a suitable alternative r-DSPE material to primary secondary amine (PSA). This method was validated on cabbage, spinach, grape and orange spiked at concentration levels of 0.02 and 0.2mg/kg. The recoveries of 30 pesticides were in the range of 71–110%, with relative standard deviations (RSDs, n=5) lower than 15%. Matrix effects were observed by comparing the slope of matrix-matched standard calibration with that of solvent. Good linearity was achieved at the concentration levels of 0.02–0.5mg/L. The limits of quantification (LOQs) and the limits of detection (LODs) for 30 pesticides ranged from 0.003 to 0.05mg/kg and 0.001 to 0.02mg/kg at the signal-to-noise ratio (S/N) of 10 and 3, respectively. The method was successfully applied to analysis real samples in Beijing. In conclusion, the modified QuEChERS method with MWCNTs cleanup step showed reliable method validation performances and good cleanup effects in this study.
•Design of a SPE–DLLME–GC–MS method for extraction and determination of 19 pesticides.•Linear calibration over 1–10,000ngL−1 and limits of detection (LODs) in the range of 0.5–1.0ngL−1.•Ultra ...enrichment factors in the range of 2362–10,593 and very high sensitivity.•Successful application to detection of pesticides in tap water, agricultural waste water, milk, honey and orange juice.
In this work, an effective preconcentration method for the extraction and determination of traces of multi-residue pesticides was developed using solid-phase extraction (SPE) coupled with dispersive liquid–liquid microextraction and gas chromatography–mass spectrometry (GC–MS). Variables affecting the performance of both extraction steps such as type and volume of elution and extraction solvents, breakthrough volume, salt addition, extraction time were thoroughly investigated. The proposed method resulted in good linearities (R2>0.9915) over the ranges of 1–10,000ngkg−1, limits of detection (LODs) in the range of 0.5–1.0ngkg−1 at S/N=3, and precision of RSD% of ⩽11.8. Under optimal conditions, the preconcentration factors were obtained in the range of 2362–10,593 for 100mL sample solutions. Comparison of the proposed method with other ones demonstrated that SPE–DLLME method provides higher extraction efficiency and larger preconcentration factor for determination of pesticides residues. Further, it is simple, inexpensive, highly sensitive, and can be successfully applied to separation, preconcentration and determination of the pesticides (and other noxious materials) in different real food samples.
This review is an overview of the recent advances of gas chromatography in essential oil analysis; in particular, it focuses on both the new stationary phases and the advanced analytical methods and ...instrumentations. A paragraph is dedicated to ionic liquids as gas chromatography stationary phases, showing that, thanks to their peculiar selectivity, they can offer a complementary contribution to conventional stationary phases for the analysis of complex essential oils and the separation of critical pairs of components. Strategies to speed‐up the analysis time, thus answering to the ever increasing request for routine essential oils quality control, are also discussed. Last but not least, a paragraph is dedicated to recent developments in column miniaturization in particular that based on microelectromechanical‐system technology in a perspective of developing micro‐gas chromatographic systems to optimize the energy consumption as well as the instrumentation dimensions. A number of applications in the essential oil field is also included.
The present study was to analyze the water dynamics of Tricholoma matsutake Singer during hot air drying by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI), and to ...investigate the volatile compounds in the pileus, upper stipe and lower stipe of fresh and dried Tricholoma matsutake Singer by headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction-gas chromatography–mass spectrometry (HS-SPME-GC–MS). Fresh samples were dried at 60 °C for 12 h. With the T2i relaxation times decreasing, the water migrated from the inner toward the periphery and then expelled during drying. The characteristic volatiles fingerprints of different parts of fresh and dried samples were established by HS-GC-IMS. The significant differences in volatile compounds were observed among different parts of the fresh sample and C8 compounds (70%–97%) were the principal components. After drying, the concentration of C8 compounds dramatically decreased and some volatile compounds (hexanal, heptanal, 2(5H)-furanone, acetophenone, nonanal, benzeneacetaldehyde) were formed. Thus, hot air treatment affected the volatile compounds in Tricholoma matsutake Singer.
Display omitted
•Water dynamics were detected by LF-NMR & MRI during drying.•Fingerprints of Tricholoma matsutake Singer were established by HS-GC-IMS.•Differences in volatiles of three parts were analyzed by HS-GC-IMS and HS-SPME-GC–MS.•C8 compounds decreased dramatically after drying.
Volatile flavor compounds determine the holistic, unique, sensory characteristic of fermented food. The characteristic volatiles across the fermentation process of Dongbei Suancai (DS) were ...investigated by headspace‐gas chromatography‐ion mobility spectrometry (HS‐GC‐IMS) combined with principal component analysis (PCA). A total of 19 representative flavor substances were identified in the samples. The differences of volatiles in naturally and inoculated‐fermented DS from different fermentation stages were detected. Ethyl acetate, ethyl butanoate, ethyl 3‐methyl butanoate, acetone, butanone, 2, 3‐butanedione, and dimethyl disulfide are important volatile substances in DS, which were all found to be formed in the prophase of fermentation. As fermentation proceeds, inoculated DS showed an improved flavor with ester aromatic substances becoming enriched, including propyl bytanoate and ethyl hexanoate. Furthermore, inoculated fermentation leads to a typical component, namely 3‐methylbutanol, being generated after the addition of Lactobacillus Plantarum LND 399 as a starter. The PCA was subsequently conducted based on the signal intensity of the identified volatile substances and showed that DS samples were distinguished favorably in mutually independent comparative spaces. This study revealed that the combination of HS‐GC‐IMS and PCA is an effective tool for analysis of the characteristic volatiles in DS samples.
Practical Application
This study has shown that the combination of HS‐GC‐IMS and PCA is an effective tool for analysis of the characteristic volatiles in DS samples. This will provide a useful method for the identification and classification of DS flavor.
Mass spectrometry-based metabolomics approaches can enable detection and quantification of many thousands of metabolite features simultaneously. However, compound identification and reliable ...quantification are greatly complicated owing to the chemical complexity and dynamic range of the metabolome. Simultaneous quantification of many metabolites within complex mixtures can additionally be complicated by ion suppression, fragmentation and the presence of isomers. Here we present guidelines covering sample preparation, replication and randomization, quantification, recovery and recombination, ion suppression and peak misidentification, as a means to enable high-quality reporting of liquid chromatography- and gas chromatography-mass spectrometry-based metabolomics-derived data.
Pyrolysis of plastic packaging waste yields a liquid product that can be processed in steam crackers producing light olefins and hence closing the loop towards new virgin plastics. However, there is ...a lack of knowledge on how the plastic waste composition affects the pyrolysis oil quality regarding hydrocarbon composition and contaminant concentrations. The associated uncertainty is a key reason why thermochemical recycling of contaminated plastic waste is not yet industrially established. In this study, post-consumer plastic packaging waste fractions, namely mixed polyolefins (MPO), polyethylene (PE), and polypropylene (PP) were processed in a continuous pilot-scale pyrolysis unit and the pyrolysis oils subsequently characterized using advanced analytical techniques such as two-dimensional gas chromatography. Substantial amounts of branched olefins (~63 wt%) and diolefins (~20 wt%) were detected in the pyrolysis oil of PP-rich waste, while PE-rich waste produced high amounts of linear paraffins (~34 wt%) and olefins (~26 wt%). Furthermore, significant amounts of nitrogen, oxygen, chlorine, iron, sodium and silicon were detected in the pyrolysis oils exceeding feedstock specifications for industrial steam crackers by orders of magnitude. The results show that next to improved waste sorting and separation processes, pre- and post-treatment techniques are required to produce pyrolysis products suitable for chemical processing.
Display omitted
•Pyrolysis of polyolefinic post-consumer plastic packaging waste.•Comprehensive two-dimensional gas chromatography coupled to various detectors.•PP-pyrolysis yields highly branched olefins, PE-pyrolysis mostly linear compounds.•Nitrogen, oxygen, chlorine, iron, sodium and silicon most important contaminants.•Upgrading or dilution needed when using pyrolysis oils as steam cracker feedstocks.
To characterize the aroma of cherry wine, five samples were analyzed by quantitative descriptive sensory analysis, gas chromatography–mass spectrometry (GC–MS) and gas chromatography–olfactometry ...(GC–O). The aroma of cherry wines was described by 6 sensory terms as fruity, sour, woody, fermentation, cameral and floral. Fifty-one odor-active (OA) compounds were detected by GC–O and quantified by GC–MS, and 45 of them were identified. Twenty-nine OA compounds having more than 50% detection frequency were selected as specific compounds correlated to sensory attributes by partial least squares regression (PLSR). The correlation result showed ethyl 2-methyl propionate, 2,3-butanedione, ethyl butyrate, ethyl pentanoate, 3-methyl-1-butanol, ethyl hexanoate, 3-hydroxy-2-butanone, ethyl lactate, 1-hexanol, (Z)-3-hexen-1-ol, ethyl hydroxyacetate, acetic acid, furfural, 2-ethyl-1-hexanol, benzaldehyde, propanoic acid, butanoic acid, guaiacol, beta-citronellol, hexanoic acid, 2-methoxy-4-methylphenol, 2-ethyl-3-hydroxy-4H-pyran-4-one, ethyl cinnamate, 2-methoxy-4-vinylphenol were typical OA compounds, which covaried with characteristic aroma of cherry wines.
PDF
