A review of food contamination with nitrated and oxygenated polycyclic aromatic hydrocarbons: toxicity, analysis, occurrence, and risk assessment

Prolonged exposure to polycyclic aromatic hydrocarbons (PAHs) and their derivatives, particularly nitrated polycyclic aromatic hydrocarbons (NPAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs), can result in adverse health effects and may carry higher toxicity risks compared to PAHs alone. Various extraction methods have been utilized for PAHs derivatives from food samples. The analytes are then analyzed using gas chromatography/mass spectrometry and high-performance liquid chromatography techniques. PAHs derivatives are increasingly being detected in the environment, prompting scrutiny from numerous researchers. Similarly, their presence in food is becoming a significant concern. The elevated levels of PAH derivatives found in smoked food may result in detrimental dietary exposure and pose potential health hazards. Furthermore, investigating the level of exposure to these contaminants in food is imperative, as their consumption by humans carries inherent risks. Consequently, this review concentrates on the toxicity, analysis, occurrence, and risk evaluation of NPAHs and OPAHs present in food sources.

Microextraction techniques for occupational biological monitoring: Basic principles, current applications and future perspectives

The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers' exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.

Solid-phase microextraction - a future technique in pharmacology and coating trends

Traditional sample preparation techniques based on liquid-liquid extraction (LLE) or solid-phase extraction (SPE) often suffer from a major error due to the matrix effects caused by significant co-extraction of matrix components. The implementation of a modern extraction technique such as solid-phase microextraction (SPME) was aimed at reducing analysis time and the use of organic solvents, as well as eliminating pre-analytical and analytical errors. Solid-phase microextraction (SPME) is an innovative technique for extracting low molecular weight compounds (less than 1500 Da) from highly complex matrices, including biological matrices. It has a wide range of applications in various types of analysis including pharmaceutical, clinical, metabolomics and proteomics. SPME has a number of advantages over other extraction techniques. Among the most important are low environmental impact, the ability to sample and preconcentrate analytes in one step, simple automation, and the ability to extract multiple analytes simultaneously. It is expected to become, in the future, another method for cell cycle research. Numerous available literature sources prove that solid-phase microextraction can be a future technique in many scientific fields, including pharmaceutical sciences. This paper provides a literature review of trends in SPME coatings and pharmacological applications.

Solvent Extraction of PDMS Tubing as a New Method for the Capture of Volatile Organic Compounds from Headspace

Polydimethylsiloxane (PDMS) tubing is increasingly being used to collect volatile organic compounds (VOCs) from static biological headspace. However, analysis of VOCs collected using PDMS tubing often deploys thermal desorption, where samples are considered as 'one-offs' and cannot be used in multiple experiments. In this study, we developed a static headspace VOC collection method using PDMS tubing which is solvent-based, meaning that VOC extracts can be used multiple times and can be linked to biological activity. Using a synthetic blend containing a range of known semiochemicals (allyl isothiocyanate, (Z)-3-hexen-1-ol, 1-octen-3-one, nonanal, (E)-anethol, (S)-bornyl acetate, (E)-caryophyllene and pentadecane) with differing chemical and physicochemical properties, VOCs were collected in static headspace by exposure to PDMS tubing with differing doses, sampling times and lengths. In a second experiment, VOCs from oranges were collected using PDMS sampling of static headspace versus dynamic headspace collection. VOCs were eluted with diethyl ether and analysed using gas chromatography - flame ionization detector (GC-FID) and coupled GC - mass spectrometry. GC-FID analysis of collected samples showed that longer PDMS tubes captured significantly greater quantities of compounds than shorter tubes, and that sampling duration significantly altered the recovery of all tested compounds. Moreover, greater quantities of compounds were recovered from closed compared to open systems. Finally, analysis of orange headspace VOCs showed no qualitative differences in VOCs recovered compared to dynamic headspace collections, although quantities sampled using PDMS tubing were lower. In summary, extraction of PDMS tubing with diethyl ether solvent captures VOCs from the headspace of synthetic blends and biological samples, and the resulting extracts can be used for multiple experiments linking VOC content to biological activity.

Theory and protocol of dual mode unity solid-phase microextraction

The solid-phase microextraction (SPME) bias problem limits comprehensive analysis of volatile compounds in real samples. The study introduces dual mode unity solid-phase microextraction (DMU-SPME) as a novel SPME mode to achieve balanced extraction of both volatile and low-volatile compounds. The DMU-SPME method exhibits excellent linearity (R2 ≥ 0.994), low quantitation limits (0.12-240 μg/L), and notable stability (relative standard deviations below 20 % for both intra-day and inter-day analyses). In practical application to soy sauce, the DMU-SPME method identified a total of 107 compounds, encompassing all those detected by both headspace solid-phase microextraction (HS-SPME) and direct immersion solid-phase microextraction (DI-SPME). Theoretical insights indicate that DMU-SPME is less influenced by Kfs0 and Kfs in comparison to HS/DI-SPME, rendering it suitable for complex matrices containing both volatile and low-volatile compounds. In conclusion, DMU-SPME emerges as a highly effective extraction mode for analyzing volatile and low-volatile compounds in food, medical, and environmental samples.

Determination of volatile compounds in white brine cheese and ultrafiltered cheese during ripening and shelf-life using nano-adsorbent fibers

In this study, determination of aromatic compounds in cheese samples was performed by headspace solid-phase microextraction (HS-SPME) using a new adsorbent as a novel coated fiber in combination with a gas chromatography/mass spectrometry or flame ionization detector to evaluate the changes during ripening. Brine and ultrafiltrated (UF) cheese were sampled via HS-SPME and analyzed by gas chromatography/mass spectrometry. Polysulfone and mesoporous carbon nitride were used as two types of fibers for coating. The results showed that the pH had significant decreased during the 120 days for brine cheese (p < 0.001), and during the 90 days (p < 0.001) for UF cheese. Acidity was relatively stable during the ripening period for both cheeses (p > 0.05). Protein content decreased during the ripening period for both cheeses (p < 0.001). Moisture content also significantly decreased during the ripening period for both cheeses (p < 0.001). 74 compounds were identified in brine cheese and 27 major components in UF cheese. Fatty acids were the predominant components, followed by aldehydes (n: 17, 22.9%), alcohol (n; 12, 16.2%), ester (n: 11, 14.8%), alkane (n: 7, 9.4%), and ketone (n: 6, 8.1%) for white brine cheese, while for UF cheese fatty acid (n: 12, 44.4%) and aldehyde (n: 5, 18.5%), alcohol (n: 3, 11.1%), ketone (n: 3, 11.1%), ester (n: 2, 7.4%) and alkane (n: 1, 3.7%).

Embedding Mixed Sorbents in Binder: Solid-Phase Microextraction Coating with Wide Extraction Coverage and Its Application in Environmental Water Analysis

Solid-phase microextraction (SPME) is a simple and highly effective sample-preparation technique for water analysis. However, the extraction coverage of a given SPME device with a specific coating can be an issue when analyzing multiple environmental contaminants. Therefore, instead of synthesizing one sorbent material with dual or multiple functions, we investigated a new strategy of preparing SPME blades using a homogeneous slurry made by mixing three different sorbent particles─namely, hydrophobic/lipophilic balanced (HLB), HLB-weak cationic exchange (HLB-WCX), and HLB-weak anionic exchange (HLB-WAX)─with a polyacrylonitrile (PAN) binder. The developed coating is matrix compatible, as the binder functions not only as a glue for immobilizing the sorbent particles but also as a porous filter, which only allows small molecules to enter the pores and interact with the particles, thus avoiding contamination from large elements. The results confirmed that the proposed mixed-coating SPME device provides good extraction performance for polar and nonpolar as well as positively and negatively charged compounds. Based on this device, three comprehensive analytical methodologies─high-throughput SPME-LC-MS/MS (for the quantitative analysis of targeted drugs of abuse and artificial sweeteners), in-bottle SPME-LC-high resolution MS (HRMS) (for the untargeted screening of organic contaminants), and on-site drone sampling SPME-LC-HRMS (for on-site sampling and untargeted screening)─were developed for use in environmental water analysis. The resultant data confirm that the proposed strategies enable comprehensive water quality assessment by using a single SPME device.

Metabolomics of natural samples: A tutorial review on the latest technologies

Metabolomics is the study of metabolites present in a living system. It is a rapidly growing field aimed at discovering novel compounds, studying biological processes, diagnosing diseases, and ensuring the quality of food products. Recently, the analysis of natural samples has become important to explore novel bioactive compounds and to study how environment and genetics affect living systems. Various metabolomics techniques, databases, and data analysis tools are available for natural sample metabolomics. However, choosing the right method can be a daunting exercise because natural samples are heterogeneous and require untargeted approaches. This tutorial review aims to compile the latest technologies to guide an early-career scientist on natural sample metabolomics. First, different extraction methods and their pros and cons are reviewed. Second, currently available metabolomics databases and data analysis tools are summarized. Next, recent research on metabolomics of milk, honey, and microbial samples is reviewed. Finally, after reviewing the latest trends in technologies, a checklist is presented to guide an early-career researcher on how to design a metabolomics project. In conclusion, this review is a comprehensive resource for a researcher planning to conduct their first metabolomics analysis. It is also useful for experienced researchers to update themselves on the latest trends in metabolomics.

Application of Sorbent-Based Extraction Techniques in Food Analysis

This review presents an outline of the application of the most popular sorbent-based methods in food analysis. Solid-phase extraction (SPE) is discussed based on the analyses of lipids, mycotoxins, pesticide residues, processing contaminants and flavor compounds, whereas solid-phase microextraction (SPME) is discussed having volatile and flavor compounds but also processing contaminants in mind. Apart from these two most popular methods, other techniques, such as stir bar sorptive extraction (SBSE), molecularly imprinted polymers (MIPs), high-capacity sorbent extraction (HCSE), and needle-trap devices (NTD), are outlined. Additionally, novel forms of sorbent-based extraction methods such as thin-film solid-phase microextraction (TF-SPME) are presented. The utility and challenges related to these techniques are discussed in this review. Finally, the directions and need for future studies are addressed.

Dispersant-First Dispersive Liquid-Liquid Microextraction (DF-DLLME), a Novel Sample Preparation Procedure for NDMA Determination in Metformin Products

Since December 2019, global batch recalls of metformin pharmaceutical products have highlighted an urgent need to control N-nitrosodimethylamine (NDMA) contamination to demonstrate patient safety and maintain supply of this essential medicine. Due to their formulation, the metformin extended-release products present difficult analytical challenges for conventional sample preparation procedures, such as artefactual (in-situ) NDMA formation, gelling, and precipitation. To overcome these challenges, a new version of dispersive liquid-liquid microextraction (DLLME) termed dispersant-first DLLME (DF-DLLME) was developed and optimized for the analysis of NDMA in metformin extended-release products using a detailed Design of Experiments (DoE) to optimize sample preparation. Gas chromatography-high resolution accurate mass-mass spectrometry (GC-HRAM-MS) combined with automated DF-DLLME were successfully applied to monitor the NDMA levels of two different metformin extended-release AstraZeneca products to ultra-trace levels (parts per billion). The additional benefits associated with DF-DLLME, which include automation, time/costs saving, and greener sample preparation, make this novel technique easier to transfer from a development to Quality Control (QC) environment. In addition, this also offers an attractive candidate for the wider platform analysis of N-nitrosamines in pharmaceutical drug products.

Volatile compounds from soybeans under multiple on herbivores infestations attract the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Plant-induced resistance can be an important component of soybean mites biological control programs. This work evaluates the preference of predatory mite Neoseiulus californicus (Acari: Phytoseiidae) to soybean plants under single and multiple herbivory conditions by two-spotted spider mite Tetranychus urticae (Acari: Tetranychidae), and velvetbean caterpillar Anticarsia gemmatalis (Lepidoptera: Noctuidae). Using a Y olfactometer, the following scenarios were evaluated: soybean with no infestation and soybean infested with A. gemmatalis; soybean infested with T. urticae and A. gemmatalis, and soybean infested with T. urticae and with both T. urticae and A. gemmatalis. Volatile compounds released by plants were analyzed and identified by a Trace GC Ultra gas chromatograph coupled to a mass spectrometer with a solid phase micro-extraction ion-trap. The predatory mite N. californicus preferred soybean plants infested with T. urticae compared to those infested with A. gemmatalis. Multiple infestation did not interfere with its preference to T. urticae. Multiple herbivory of T. urticae and A. gemmatalis modified the chemical profile of volatile compounds emitted by soybean plants. However, it did not interfere with the search behavior of N. californicus. Out of the 29 identified compounds only five promoted predatory mite response. Thus, regardless of single or multiple herbivory by T. urticae with or without A. gemmatalis, the indirect induced resistance mechanisms operate similarly. As such, this mechanism contributes to an increase in the encounter rate between predator and prey for N. Californicus and T. urticae, and the efficacy of biological control of mites on soybean.

Temperature-dependent alcohol acyltransferase reactions as the main enzymatic way to produce short-chain (C4-C8) and medium-chain (C9-C13) esters over the whole Daqu-making process

BACKGROUND

The ester-synthesis enzymes influenced by environmental factors during Daqu-making process largely determine the flavor of Chinese liquor, but the main ester-synthesis enzyme and its key influencer remain unclear. Here, the volatile ester profiles over the whole Daqu-making process, under different treatments, for at least 90 days, were carefully analyzed, and the potential ester-synthesis enzymes, as well as their dependently environmental factors, were explored.

RESULTS

In the detected 46 volatile esters, only the short-chain (C4-C8) and medium-chain (C9-C13) ester content obviously changed, as the primary contributor discriminating different samples. Their trends were both consistent with that of the alcohols and the primary metabolism, which included alcohol acyltransferases (AATs) reaction with alcohols and acyl-CoAs as the substrates. Among the potential ester-synthesis enzymes, the typical AAT activity also exhibited the highest correlation with the short- and medium-chain esters (r > 0.78, P < 0.05). The Mantel test between environmental factors and ester production showed that temperature of Daqu was directly correlated with the short-chain esters (r = 0.58, P < 0.01) and AAT activity (r = 0.56, P < 0.01). Further, the short- and medium-chain ester content in Daqu under the treatment nearer to the reported optimal temperature of 40-50 °C of AATs reaction was overall higher than that of the other treatment Daqu.

CONCLUSION

This study revealed that the temperature-dependent AATs reaction was the main enzymatic method producing the short- and medium-chain esters over the whole Daqu-making process. The results could contribute to the flavor improvement of Baijiu. © 2022 Society of Chemical Industry.

Characterization of volatiles in flowers from four Rosa chinensis cultivars by HS-SPME-GC × GC-QTOFMS

Rosa chinensis cultivars with volatile aromas are important resources in the perfume industry. The four rose cultivars introduced to Guizhou province are rich in volatile substances. In this study, volatiles from four Rosa chinensis cultivars were extracted using headspace-solid phase microextraction (HS-SPME), and analyzed with two-dimensional gas chromatography quadrupole time of flight mass spectrometry (GC × GC-QTOFMS). A total of 122 volatiles were identified; the main compounds in these samples were benzyl alcohol, phenylethyl alcohol, citronellol, beta-myrcene and limonene. A total of 68, 78, 71, and 56 volatile compounds were identified in Rosa 'Blue River' (RBR), Rosa 'Crimson Glory' (RCG), Rosa 'Pink Panther' (RPP), and Rosa 'Funkuhr' (RF) samples, respectively. The total volatile contents were in the following order: RBR > RCG > RPP > RF. Four cultivars exhibited similar volatility profiles, with alcohols, alkanes, and esters as the major chemical groups, followed by aldehydes, aromatic hydrocarbons, ketones, benzene, and other compounds. Alcohols and aldehydes were quantitatively the two most abundant chemical groups that included the highest number and highest content of compounds. Different cultivars have different aromas, and RCG had high contents of phenyl acetate, rose oxide, trans-rose oxide, phenylethyl alcohol and 1,3,5-trimethoxybenzene, characterized by floral and rose descriptors. RBR contained a high content of phenylethyl alcohol, and RF contained a high content of 3,5-dimethoxytoluene. Hierarchical cluster analysis (HCA) of all volatiles showed that the three cultivars (RCG, RPP, and RF) had similar volatile characteristics and were significantly different from RBR. Differential metabolites among cultivars were screened based on the OPLS-DA model, and there were six main enriched pathways of differential metabolites: biosynthesis of secondary metabolites, monoterpenoid biosynthesis, metabolic pathways, limonene and pinene degradation, sesquiterpenoid and triterpenoid biosynthesis, and alpha-linolenic acid metabolism. The biosynthesis of secondary metabolites is the most differential metabolic pathway.

Polyurethane Foam as a Novel Material for Ochratoxin A Removal in Tea and Herbal Infusions-A Quantitative Approach

A novel solid-phase extraction methodology followed by UHPLC-MS/MS has been developed for Ochratoxin A (OTA) analysis in herbal infusions. For this purpose, a commercial polyurethane foam (PUF) was used as sorbent, and the experimental conditions were fully optimized. The strategy was satisfactory for reducing the matrix effect and allowed for OTA quantification in black tea and herbal infusions, with suitable recoveries and quantitation limits in agreement with those required by the maximum levels allowed by current regulations. The achieved results demonstrated the unprecedented use of polyurethane foam as an effective alternative for OTA retention and quantification in herbal infusions with the advantages of simple preparation, time saving, sustainability, and low cost for routine analysis.

Full Evaporative Vacuum Extraction─A Quantitative and Green Approach for Analysis of Semivolatile Organic Compounds in Drinking Water and Surface Water Using GC-MS

Full evaporative vacuum extraction (FEVE) was developed in this work for analysis of a broad range of semivolatile organic compounds (SVOCs) in drinking water and surface water. Sorbent pens are used in a two-stage process that first evaporates the sample matrix through sorbent beds under vacuum to recover the lighter SVOCs, followed by the application of a higher temperature and stronger vacuum to the sample vial to recover the remaining heavier SVOCs once the matrix has evaporated. After extraction, the sorbent pens are desorbed into a GC-MS using a uniquely designed "splitless" delivery system to maximize sensitivity. Critical extraction and desorption parameters that affect the method performance were optimized. After FEVE, the sorbent pens can be stored for 7-10 days at room temperature while maintaining a less than 15% loss in analyte recovery. As a proof of concept, 10 drinking water and surface water samples were analyzed using this method. 69 analytes were detected in these water samples, with the highest concentration of 1986 ng/L for bromacil. Heptachlor epoxide, chlorpyrifos, metolachlor, butachlor, and 2,3',4',5-tetrachlorobiphenyl were detected in four samples. None of the analytes were above the health and safety thresholds set by California Proposition 65.

Recruiting chemical grafting method for surface modification of stainless steel to fabricate a selective sorbent for solid phase microextraction of mercury metal ion

Keeping selectiveness and efficiency in view with solid-phase microextraction (SPME) of metal ions, this work was aimed at synthesis of a novel modified sorbent on a stainless-steel surface to fabricate a selective and efficient fiber for SPME of mercury ions from real food and biological samples. After the confirmation of sorbent structure grafted on the stainless-steel surface, by different techniques, the synthesized fiber was utilized for extraction and preconcentration of mercury before its measurement by an inductively coupled plasma-optical emission spectroscopy (ICP-OES). For optimizing the efficiency, the influences of various factors on the extraction of Hg (II) ion were scrutinized. The optimized values used for extraction were pH 7.0, adsorption time 8 min, desorption time 5 min, 5 mL of eluent solvent containing nitric acid with concentration of 0.5 mol L^-1, and stirring rate of 300 rpm. Underneath optimum condition, the relative standard deviation for 30 extractions, done by one synthesized fiber, was calculated to be 2.89% and for five extractions, done by 5 synthesized fibers, was calculated to be 1.78%. The high performance of the synthesized fiber was checked with high recoveries obtained from 30 successive sorption-desorption cycles, using a unique synthesized fiber. Finally, the suggested procedure was triumphally exploited for extraction and pre-concentration of Hg (II) ion in real food and biological samples.

Comparative Study on Chemical Constituents of Ginseng Flowers with Four Consecutive Cultivation Age

The harvest period of cultivated ginseng is generally 4-6 years. Ginseng flowers (GFs), the nonmedicinal parts, are usually removed every autumn, in which components are generally believed to stay unchanged with the increasing cultivation age. Recently, few documents were reported on the variation of volatile organic compounds (VOCs) and other components about ginseng flowers. This study had an insight into the variation of the chemical constituents with the cultivation ages through the comparison of the volatile organic compounds, gross ginsenosides, crude polysaccharide, and gross proteins of ginseng flowers from 3-, 4-, 5-, and 6-yr-old (GF3, GF4, GF5, and GF6) which were conducted by headspace solid-phase microextraction-gas chromatography-triple quadrupole mass spectrometry (HS-SPME-GC-QQQ/MS) and spectroscopic analysis combined with multivariate statistical analysis, including one-way ANOVA analysis and T test. The results indicated that the crude polysaccharide contents raised significantly depending on cultivation age except 6-yr-old, whereas the gross ginsenosides and the gross protein content were indistinctive. According to the peak intensity of determined VOCs, the contents of most differential compounds arranged in an order from high to low are GF3, GF4, GF5, and GF6, such as the compounds 2-15, 17-19, 22, and 25-26, therefore, they can be inferred that they are important markers to identify the age of GFs. 461 common differential compounds were gained and 26 common volatile organic compounds were identified with RSI >800 and RI and RIx no more than 30, including alcohols (such as 11, 12, and 15), sesquiterpenes (such as 2, 3, and 4), esters (such as 1 and 26), naphthalene and naphthol (such as 7 and 20), which had potential effects on curing Alzheimer's disease, inflammatory diseases, and prostate cancer based on network pharmacology analysis. This paper firstly revealed the variation rules of constitutions of GFs, which may provide a reference for the harvest and making rational application.

Rapid detection of Escherichia coli in dairy milk using static headspace-comprehensive two-dimensional gas chromatography

A new approach is introduced for rapid and reliable bacteria detection in food. Namely, static headspace-comprehensive two-dimensional gas chromatography (HS-GC × GC) with backflushing. The introduced approach provides fast detection of Escherichia coli (E. coli) in enriched ultra-high-temperature processed (UHT) dairy milk. The presence of E. coli may be indicated by detecting microbial volatile organic compounds emanating from test solutions inoculated with E. coli. In the present investigation, HS-GC × GC analysis is preceded by conventional enrichment in nutrient broth and inoculated samples are clearly discernable from controls following as little as 15 h sample enrichment. Headspace equilibration for 28 min followed by an 8 min GC × GC analysis of enriched test solutions reduces time-to-response by approximately one full day compared to conventional culture-based methods. The presence of ethanol, 1-propanol, and acetaldehyde may be used as a putative marker of E. coli contamination in milk and the introduced approach is able to detect single-cell initial bacterial load. Faster, reliable detection of pathogens and/or spoilage microbes in food products is desirable for the food industry. The described approach has great potential to complement the conventional workflow and be utilised for rapid microbial screening of foodstuff.

Development of multi-residue gas chromatography coupled with mass spectrometry methodologies for the measurement of 15 chemically different disinfection by-products (DBPs) of emerging concern in drinking water from two different Portuguese water treatment plants

In water treatment plants (WTPs), chemical agents, such as chlorine and ozone, might react with organic matter and anthropogenic contaminants, forming a high diversity of disinfection by-products (DBPs). Due to the potential toxicological effects, the identification of unregulated DBPs (UR-DBPs) is critical to help water managers in the selection of effective water treatment processes, contributing to improving water safety plans. Given the limited validated analytical methods to detect UR-DBPs, here we developed new multi-residue gas chromatography coupled with mass spectrometry methodologies for the detection and quantification of 15 UR-DBPs, including aldehydes, haloketones (HKs), nitrosamines and alcohols, in drinking water matrices. Solid-phase extraction (SPE), for the nitrosamine group, and solid-phase micro extraction (SPME), for the remaining DBPs, were used as sample preparation methods. The developed methodologies allowed the quantification of target UR-DBPs at trace concentration levels (ng L^-1), with method quantification limits (MQLs) ranging from 14.4 ng L^-1 to 26.0 ng L^-1 (SPE-GC-MS) and 2.3 ng L^-1 and 1596 ng L^-1 (SPME-GC-MS). The methods were applied to different drinking water matrices, considering distinct delivery points of EPAL - Empresa Portuguesa das Águas Livres WTPs. Overall, the aldehyde group, represented by decanal, nonanal and 2-ethylheaxanal, showed the highest occurrence, followed by HKs and nitrosamines. The results of this study suggested that the formation of these UR-DBPs should be further monitored in WTPs.

Solid-Phase Microextraction—Gas Chromatography Analytical Strategies for Pesticide Analysis

Due to their extensive use and the globalized commerce of agricultural goods, pesticides have become a global concern. Despite the undoubtful advantages of their use in agricultural practices, their misuse is a threat to the environment and human health. Their analysis in environmental samples and in food products continues to gain interest in the analytical chemistry community as they are challenging matrices, and legal concentration limits are particularly low (in the order of ppb). In particular, the use of solid-phase microextraction (SPME) has gained special attention in this field thanks to its potential to minimize the matrix effect, while enriching its concentration, allowing very low limits of detection, and without the need of a large amount of solvents or lengthy procedures. Moreover, its combination with gas chromatography (GC) can be easily automated, making it a very interesting approach for routine analysis. In this review, advances and analytical strategies for the use of SPME coupled with GC are discussed and compared for the analysis of pesticides in food and environmental samples, hopefully encouraging its further development and routine application in this field.

Characterization of the Volatilome of Tuber canaliculatum Harvested in Quebec, Canada

The first detailed characterization of volatile compounds from Tuber canaliculatum, a truffle newly grown in Quebec, Canada, was performed with headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC/MS). A total of 30 compounds were identified, making up more than 98% of the volatile extract. The volatilome of T. canaliculatum is dominated by (E)-1-methylthio-1-propene, (Z)-1-methylthio-1-propene, dimethyl disulfide, and 1-octen-3-ol. It also includes six compounds identified for the first time in truffles, namely, 4-hydroxy-4-methyl-2-pentanone, pentyl propanoate, (Z)-1-methyl-2-(prop-1-en-1-yl)disulfide, (E)-1-methyl-2-(prop-1-en-1-yl)disulfide, (Z)-1-methyl-3-(prop-1-en-1-yl)trisulfide, and (E)-1-methyl-3-(prop-1-en-1-yl)trisulfide. With the growing interest in gastronomy in truffles in North America, it is becoming important to gather knowledge for identification purposes and to delineate the key volatile compounds responsible for the aroma of North American truffles, especially the newly harvested T. canaliculatum.

Marker Substances in the Aroma of Truffles

The aim of this study was to identify specific truffle marker substances within the truffle aroma. The aroma profile of different truffle species was analyzed using static headspace sampling with gas chromatography mass spectrometry analysis (SHS/GC-MS). Possible marker substances were identified, taking the additional literature into account. The selected marker substances were tested in an experiment with 19 truffle dogs. The hypothesis “If trained truffle dogs recognize the substances as supposed truffles in the context of an experiment, they can be regarded as specific” was made. As it would be nearly impossible to investigate every other possible emitter of the same compounds to determine their specificity, this hypothesis was a reasonable approximation. We were interested in the question of what it is the dogs actually search for on a chemical level and whether we can link their ability to find truffles to one or more specific marker substances. The results of the dog experiment are not as unambiguous as could have been expected based on the SHS/GC-MS measurements. Presumably, the truffle aroma is mainly characterized and perceived by dogs by dimethyl sulfide and dimethyl disulfide. However, as dogs are living beings and not analytical instruments, it seems unavoidable that one must live with some degree of uncertainty regarding these results.

Elicitation of Innate Immunity by a Bacterial Volatile 2-Nonanone at Levels below Detection Limit in Tomato Rhizosphere

Bacterial volatile compounds (BVCs) exert beneficial effects on plant protection both directly and indirectly. Although BVCs have been detected in vitro, their detection in situ remains challenging. The purpose of this study was to investigate the possibility of BVCs detection under in situ condition and estimate the potentials of in situ BVC to plants at below detection limit. We developed a method for detecting BVCs released by the soil bacteria Bacillus velezensis strain GB03 and Streptomyces griseus strain S4-7 in situ using solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS). Additionally, we evaluated the BVC detection limit in the rhizosphere and induction of systemic immune response in tomato plants grown in the greenhouse. Two signature BVCs, 2-nonanone and caryolan-1-ol, of GB03 and S4-7 respectively were successfully detected using the soil-vial system. However, these BVCs could not be detected in the rhizosphere pretreated with strains GB03 and S4-7. The detection limit of 2-nonanone in the tomato rhizosphere was 1 µM. Unexpectedly, drench application of 2-nonanone at 10 nM concentration, which is below its detection limit, protected tomato seedlings against Pseudomonas syringae pv. tomato. Our finding highlights that BVCs, including 2-nonanone, released by a soil bacterium are functional even when present at a concentration below the detection limit of SPME-GC-MS.

Contribution to the determination of tributyltin in water by stir bar sorptive extraction‒thermal desorption‒gas chromatography‒tandem mass spectrometry

An environmentally friendly method was developed to determine tributyltin (TBT) in water at the levels required by the European Union Water Framework Directive (EU WFD) using stir bar sorptive extraction (SBSE) in combination with thermal desorption‒gas chromatography‒triple quadrupole tandem mass spectrometry. The main focus of the method development was on addressing some aspects of reducing blank values (minimizing the use of chemicals, glassware cleaning, pretreatment of sorptive stir bars) and optimizing the SBSE procedure variables (sample volume, polarity of sample solution, extraction time). The performance of the method was studied in terms of linearity, matrix effect, method limits and accuracy (precision and trueness) using MilliQ, tap and surface water. TBT quantification limit for the studied matrices ranged from 0.049 to 0.055 ng L^‒1 and repeatability (RSD%, n = 10) and recovery at the environmental quality standard (EQS) concentration of 0.2 ng L^‒1 were in the range of 6‒18% and 88‒107%, respectively, indicating good performance of the method. The matrix effect of river water (‒78%) and artificial seawater (‒83%) compared to MilliQ water showed the necessity to use a matrix-matched calibration when analysing TBT in surface water samples. The developed sample preparation was further evaluated for greenness using the recently introduced AGREEprep assessment, which revealed a much greener performance of the proposed method over the compared CEN/TS 16692 method. The method meets the requirements of the EU WFD and is suitable for monitoring, evaluation and classification of the chemical status of surface waters.

Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples

Developing effective and green methods for food analysis and separation has become an urgent issue regarding the ever-increasing concern of food quality and safety. Ionic liquids (ILs) are a new chemical medium and soft functional material developed under the framework of green chemistry and possess many unique properties, such as low melting points, low-to-negligible vapor pressures, excellent solubility, structural designability and high thermal stability. Combining ILs with extraction techniques not only takes advantage of ILs but also overcomes the disadvantages of traditional extraction methods. This subject has attracted intensive research efforts recently. Here, we present a brief review of the current research status and latest developments regarding the application of IL-assisted microextraction, including dispersive liquid–liquid microextraction (DLLME) and solid-phase microextraction (SPME), in food analysis and separation. The practical applications of ILs in determining toxic and harmful substances in food specimens with quite different natures are summarized and discussed. The critical function of ILs and the advantages of IL-based microextraction techniques over conventional extraction techniques are discussed in detail. Additionally, the recovery of ILs using different approaches is also presented to comply with green analytical chemistry requirements.

A Review of Extraction Methods and Analytical Techniques for Styrene and its Metabolites in Biological Matrices

We reviewed the toxicokinetics of styrene to introduce reliable surrogates for biological monitoring of styrene workers. Also, extraction techniques and analytical methods for styrene and its metabolites have been discussed. Sample preparation is the main bottleneck of the analytical techniques for styrene and its metabolites. While some microextraction methods have been developed to overcome such drawbacks, some still have limitations such as long extraction time, fiber swelling and breakage, and the cost and the limited lifetime of the fiber. Among all, microextraction by packed sorbents coupled with high performance liquid chromatography with ultraviolet detection (MEPS-HPLC-UV) can be the method of choice for determining styrene metabolites. Few studies investigated unchanged styrene in breath samples. Chemical determination in exhaled breath provides new insights into organ toxicity in workers with inhalation exposures and can be considered as a fascinating tool in risk assessment strategies. Taking blood samples is invasive and less accepted by workers than other samples. In contrast, breath analysis is the most attractive method for workers because breath samples are easy to collect and non-invasive, and does not require worker transfer to health facilities. Therefore, developing selective and sensitive methods for determining styrene in breath samples is recommended for future studies.

Assessing food authenticity through protein and metabolic markers

This chapter aims to address an issue of ancient origins, but more and more topical in a globalized world in which consumers and stakeholders are increasingly aware: the authenticity of food. Foods are systems that can also be very complex, and verifying the correspondence between what is declared and the actual characteristics of the product is often a challenging issue. The complexity of the question we want to answer (is the food authentic?) means that the answer is equally articulated and makes use of many different analytical techniques. This chapter will consider the chemical analyses of foods aimed at guaranteeing their authenticity and will focus on frontier methods that have been developed in recent years to address the need to respond to ever-increasing guarantees of authenticity. Targeted and non-targeted approaches will be considered for verifying the authenticity of foods, through the study of different classes of constituents (proteins, metabolites, lipids, flavors). The numerous approaches available (proteomics, metabolomics, lipidomics) and the related analytical techniques (LC-MS, GC-MS, NMR) are first described from a more general point of view, after which their specific application for the purposes of authentication of food is addressed.

Inoculum size of co-fermentative culture affects the sensory quality and volatile metabolome of fermented milk over storage

Lacticaseibacillus paracasei PC-01 is a probiotic candidate isolated from naturally fermented yak milk in Lhasa, Tibet, and it has been shown to possess excellent milk fermentation properties. This study used Lacticaseibacillus paracasei PC-01 as a co-fermentation strain to investigate the effect of inoculum size with a commercial starter in milk fermentation on the product flavor and profile of volatile metabolites over 28 d of cold storage. Lacticaseibacillus paracasei PC-01 was allowed to ferment in pasteurized milk with or without the commercial starter (YF-L904) at 42°C until the pH decreased to 4.5. The finished fermented milks were stored at 10°C for 28 d. Milk samples were taken at hour 0 (before fermentation) and then at d 1, 14, and 28 of cold storage. Different inoculum sizes of Lacticaseibacillus paracasei PC-01 had no significant effect on pH or titratable acidity during storage of fermented milk. Viable counts of strain PC-01 continued to increase during cold storage of the fermented milk. Generally, as storage of fermented milk proceeded, the overall sensory quality score decreased in all groups. However, the overall sensory scores of PC-01-M were generally higher than those of other groups, suggesting that a medium dose of Lacticaseibacillus paracasei PC-01 had the most obvious effect of slowing the decline in sensory quality of fermented milk during storage. Changes in sensory scores and consumer preferences were accompanied by increases in both the quantity and variety of key volatile metabolites in fermented milk during fermentation, post-ripening (d 1), and storage. Major differentially abundant metabolites, including acetaldehyde, methyl ketones, medium-chain and short-chain fatty acids, 2,3-butanedione, and acetoin, were enriched in fermented milks rated highly in the sensory evaluation. Our data confirmed that the inoculum size of co-fermentative culture affected the sensory quality and volatile metabolome of fermented milk over storage, and an optimal range of co-fermentative culture was titrated in this work.

Solid-phase extraction techniques based on nanomaterials for mycotoxin analysis: An overview for food and agricultural products

Mycotoxin contamination is a globally concerned problem for food and agricultural products since it may directly or indirectly induce severe threats to human health. Sensitive and selective screening is an efficient strategy to prevent or reduce human and animal exposure to mycotoxins. However, enormous challenges exist in the determination of mycotoxins, arising from complex sample matrices, trace-level analytes, and the co-occurrence of diverse mycotoxins. Appropriate sample preparation is essential to isolate, purify, and enrich mycotoxins from complicated matrices, thus decreasing sample matrix effects and lowering detection limits. With the cross-disciplinary development, new solid-phase extraction strategies have been exploited and integrated with nanotechnology to meet the challenges of mycotoxin analysis. This review summarizes the advance and progress of solid-phase extraction techniques as the methodological solutions for mycotoxin analysis. Emphases are paid on nanomaterials fabricated as trapping media of SPE techniques, including carbonaceous nanoparticles, metal/metal oxide-based nanoparticles, and nanoporous materials. Advantages and limitations are discussed, along with the potential prospects. This article is protected by copyright. All rights reserved.

Detection of Volatiles by HS-SPME-GC/MS and Biological Effect Evaluation of Buddha's Hand Fruit

The present work aimed to chemically characterize and evaluate the antiradical power and biological effects of Citrus medica var. sarcodactylus essential oil (EO) and hydrolate (Hy) from exocarp as well as methanol extracts, from both exocarp and mesocarp (EEX and MEX). The whole fresh fruit was also investigated by SPME-GC/MS to describe its volatile composition. EO and Hy were analyzed by GC/MS and HS-GC/MS techniques, respectively. Limonene and γ-terpinene were found to be the most abundant compounds both in the fresh parts of the fruit and in the EO, while α-terpineol and terpinen-4-ol were in the Hy. The extracts were also rich in furan and coumarin derivatives. A good antiradical activity of all samples except Hy was detected both against ABTS·+ than DPPH·, removed up to about 50%. The antibacterial activity against Bacillus cereus and Escherichia coli was evaluated by microwell dilution method to determine MIC and MBC values. EEX and MEX showed efficacy at very high concentrations against both tested bacteria. The MIC value of EO against B. cereus was 0.5% v/v, while Hy was not able to inhibit the bacterial growth at the tested concentrations. Cytotoxicity investigated on the HL60 leukemia cell line by MTT assay provided an EC₅₀ of 1.24% v/v for EO. Interesting activity of Hy was also observed.

Measurement of trace bisphenol A in drinking water with combination of immunochromatographic detection technology and SERS method

Sensitive and selective detection of target analyte is very important in many fields such as commodity inspection and quality monitoring. In this work, based on the principle of competitive immunoassay, surface-enhanced Raman spectroscopy (SERS) was used to establish a rapid and highly sensitive method for the detection of trace amounts of bisphenol A in water. Here, Raman molecule 5,5-dithiobis-2-nitrobenzoic acid and anti-BPA antibody were conjugated with Au (core)@Ag (shell) nanoparticle to serve as SERS nanoprobe. After the SERS nanoprobe is combined with the substance to be tested, it uses the siphon effect to pass through the test line and the charging line on the test strip. And the Raman test was performed on the T line with a Raman spectrometer. The detection limitation was 0.1 pg/mL. Compared with the reported gas chromatography, liquid chromatography, fluorescence analysis, and other detection methods, SERS ICA does not demand complicated sample preparation procedures, and has the advantages of simple detection methods, quick results, High sensitivity, good specificity, and low technical demands for laboratory environment and testers. In addition, Raman spectrometers have gradually developed to be portable, making it easier to meet the needs of on-site rapid and highly sensitive detection, and will show broad prospects for applications in the fields of biomedical diagnosis and food safety monitoring.

Optimized Isolation of Safranal from Saffron by Solid-Phase Microextraction (SPME) and Rotatable Central Composite Design-Response Surface Methodology (RCCD-RSM)

Safranal is the main aroma component of saffron stigmas. It is also a great antioxidant with known pharmacological properties and is a potent indicator for the grading and authentication of saffron. In this study, the optimum extraction conditions of safranal from saffron stigmas were investigated using solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and response surface methodology (RSM). A rotatable-central composite design was applied, and a linear regression model has been used for the model building. The optimized factors were as follows: sample weight (15 mg), water volume (4 mL), exposure time in the headspace (20 min), and extraction temperature (45 °C). All factors were found significant; however, extraction temperature and exposure time were the most important for the isolation of safranal. The obtained model was successfully validated with a test set of saffron samples analyzed under the optimum extraction conditions. The optimized SPME extraction conditions of safranal found in this study contribute to the efforts towards the detection of saffron authentication and adulteration.

Determination of furanic compounds in Mopane worms, corn, and peanuts using headspace solid-phase microextraction with gas chromatography-flame ionisation detector

A headspace-solid phase microextraction - gas chromatography-flame ionisation detector (HS-SPME-GC/FID) method was developed for the simultaneous determination of furan, 2-methylfuran and 2-furaldehyde in thermally processed Mopane worms, corn, and peanuts. The optimal HS-SPME conditions with polydimethylsiloxane/carboxen/divinylbenzene (PDMS/CAR/DVB) fiber were 30 °C, 40 min and 600 rpm stirring speed. The recoveries, detection and quantification limits for the analytes in food samples were 67-106%, 0.54-3.5 µg kg^-1, and 1.8-12 µg kg^-1, respectively. These results showed that the developed method was accurate, reproducible, and sensitive for the determination of furan, 2-methylfuran and 2-furaldehyde in complex food matrices with limited interference from other components. The optimised analytical method was applied for monitoring the presence of the furanic compounds in heat-processed South African foods. Although 2-furaldehyde was not detected in food samples, the maximum concentrations of 24 and 95 µg kg^-1 were found for furan and 2-methylfuran, respectively.

Chemometrics-Based Aroma Discrimination of 14 Egyptian Mango Fruits of Different Cultivars and Origins, and Their Response to Probiotics Analyzed via SPME Coupled to GC-MS

The present study investigated the volatile organic compounds (VOCs) in 14 Egyptian mango specimens collected from three different regions and of different cultivars (cvs). VOCs were extracted via solid-phase microextraction, followed by gas chromatography-mass spectrometry analysis. The results obtained for sesquiterpene hydrocarbons' qualitative abundance were represented by 28 peaks, whereas monoterpene hydrocarbons amounted for the highest levels in most of the mango cvs. Multivariate data analyses were employed for sample classification and identification of markers. Unsupervised principal component analysis revealed that "zebdia" cv from the three origins combined together being enriched in terpinolene. Moreover, supervised orthogonal partial least square-discriminant analysis identified β-terpinene and (Z)-geranylacetone in the premium "awees" cv. The impact of probiotic bacteria on mango juice aroma was further assessed revealing no potential changes in the composition. This study provides the first comprehensive insights into Egyptian mango aroma and reveals that the cv type overcomes the geographical origin in their aroma profile.

Conductive Polymer-Based Nanocomposites as Powerful Sorbents: Design, Preparation and Extraction Applications

Conductive polymers as composite materials have been attracted tremendous attention due to their versatile and excellent features such as tunable conductivity, facile synthesis and fabrication, high chemical and thermal stability etc. These characteristics make them versatile and let them being used in numerous fields including microelectronics, optics and biosensors. Throughout the mentioned fields, conductive polymers particularly perform as effective sorbents. Although tremendous efforts have been put into this topic, to the best of our knowledge, a comprehensive up-to-date review on the applications of conductive polymers as efficient sorbents has not been reported. The main objective of this paper is to make a significant contribution to the recent literature toward the synthesis and extraction applications of conductive polymers as efficient sorbents.

In Vitro Systems for Toxicity Evaluation of Microbial Volatile Organic Compounds on Humans: Current Status and Trends

Microbial volatile organic compounds (mVOC) are metabolic products and by-products of bacteria and fungi. They play an important role in the biosphere: They are responsible for inter- and intra-species communication and can positively or negatively affect growth in plants. But they can also cause discomfort and disease symptoms in humans. Although a link between mVOCs and respiratory health symptoms in humans has been demonstrated by numerous studies, standardized test systems for evaluating the toxicity of mVOCs are currently not available. Also, mVOCs are not considered systematically at regulatory level. We therefore performed a literature survey of existing in vitro exposure systems and lung models in order to summarize the state-of-the-art and discuss their suitability for understanding the potential toxic effects of mVOCs on human health. We present a review of submerged cultivation, air-liquid-interface (ALI), spheroids and organoids as well as multi-organ approaches and compare their advantages and disadvantages. Furthermore, we discuss the limitations of mVOC fingerprinting. However, given the most recent developments in the field, we expect that there will soon be adequate models of the human respiratory tract and its response to mVOCs.

Evaluation of New, Sputtered Carbon SPME Fibers with a Multi-Functional Group Test Mixture

We report the first fabrication of sputtered carbon, solid-phase microextraction (SPME) fibers. These fibers have competitive extraction capabilities compared with the commercial carbon wide range (CWR) SPME fiber. This report also includes a demonstration of a newly developed SPME test mix that includes 15 different compounds with a wide range of functional groups and chemical properties. The fiber fabrication process involves sputtering carbon onto fused silica fibers, and the effects of throw distance on the morphology of the carbon coatings were studied. Four different carbon coating thicknesses were evaluated, with PDMS added as a stationary phase. These fibers were characterized with multiple analytical techniques, including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) goniometry, as well as headspace (HS) and direct immersion (DI)–SPME–GC–MS. The best (11.5 µm) sputtered carbon SPME fibers, with and without PDMS, were evaluated using the new evaluation mix and compared with the commercial CWR fiber and a previously sputtered/developed silicon fiber. The new probe mix helped elucidate differences among the fibers, which would have been missed by current commercial test mixes. The sputtered carbon SPME fibers showed similar functional group selectivity as commercial CWR fibers. However, the sputtered carbon fibers showed higher responses per volume compared with the commercial CWR fiber, indicating the porous morphology of the sputtered carbon has the ability to overcome large phase thickness/volume discrepancies and increase the relative recovery for various compounds.

Preparation of a new coating of graphene oxide/nickel complex on a nickelized metal surface for direct immersion solid phase microextraction of some polycyclic aromatic hydrocarbons

Background

Solid-phase microextraction (SPME) is a versatile sampling and sample preparation technology that possess a significant application in the extraction and pre-concentration of a broad range of micro-pollutants from different kind of matrices. Selection and preparation of an appropriate fiber substrate and coating materials have always been the main challenges of the SPME procedure. This paper introduces a high-efficiency metal-based SPME fiber with a new chemical coating of nickel/graphene oxide/nickel tetraazamacrocyclic complex (Ni/GO/NiTAM).

Result

The Ni/GO/NiTAM sorbent was electroless deposited onto the surface of an aluchrom (Alu) wire, and then the prepared fiber was employed for the extraction and pre-concentration of some PAHs before their HPLC–UV analysis. The prepared fiber characterization data were assessed using FE-SEM, EDX, XRD, FT-IR, and BET techniques. The method validation parameters, including the linearity range (LRs: 0.10 to 200.0 µg L⁻¹), the limit of detection (LODs: 0.03‒0.30 µg L⁻¹), and the limit of quantification (LOQs: 0.10–1.00 µg L⁻¹), under optimal conditions. The relative standard deviations (RSDs) of intra-day, inter-day, and single fiber repeatability (for the samples spiked at 25 µg L^‒1) were in the range of 0.32–2.94, 1.20–4.09, and 1.42‒4.39%, respectively. In addition, the technique recoveries (RR %) and enrichment factors (EF) were in the range of 83.10‒107.80% and 83–164, respectively.

Conclusion

The fiber fabrication was simple, and the applied materials were also economical and easily accessible. Alu metal has high physicochemical and mechanical stability and thus can be a good alternative for the substrate of the fragile commercial SPME fibers. High rigidity and durability, long service life, and high extraction capability are some of the other advantages of the offered fiber.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13065-021-00783-w.