Solid-phase Microextraction Fiber Research Articles

Monitoring the liberation of volatile organic compounds during fused deposition modeling three dimensional printing using solid-phase microextraction coupled to gas chromatography/mass spectrometry

Three-dimensional (3D) printers have gained tremendous popularity and are being widely used in offices, laboratories, and private homes. Fused deposition modeling (FDM) is among the most commonly used mechanisms by desktop 3D printers in indoor settings and relies on the extrusion and deposition of heated thermoplastic filaments, resulting in the liberation of volatile organic compounds (VOCs). With the growing use of 3D printers, concerns regarding human health have risen as the exposure to VOCs may cause adverse health effects. Therefore, it is important to monitor VOC liberation during printing and to correlate it to filament composition. In this study, VOCs liberated with a desktop printer were measured by solid-phase microextraction (SPME) combined with gas chromatography/mass spectrometry (GC/MS). SPME fibers featuring sorbent coatings of varied polarity were chosen for the extraction of VOCs liberated from acrylonitrile butadiene styrene (ABS), tough polylactic acid, and copolyester+ (CPE+) filaments. It was found that for all three filaments tested, longer print times resulted in a greater number of extracted VOCs. The ABS filament liberated the most VOCs while the CPE+ filaments liberated the fewest VOCs. Through the use of hierarchical cluster analysis and principal component analysis, filaments as well as fibers could be differentiated based on the liberated VOCs. This study demonstrates that SPME is a promising tool to sample and extract VOCs liberated during 3D printing under non-equilibrium conditions and can be used to aid in tentative identification of the VOCs when coupled to gas chromatography-mass spectrometry.

Solid‐phase microextraction and cuticular hydrocarbon differences related to reproductive activity in juniper bark borer Semanotus bifasciatus Motschulsky

AbstractCuticular hydrocarbons of Cerambycidae species can function as signals for sex recognition. Little is known about the copulatory signals of the juniper bark borer Semanotus bifasciatus, a major economic threat to Platycladus orientalis Franco in China. Here, we investigated the cuticular hydrocarbons of both sexes of S. bifasciatus to determine the chemically mediated mating signals using the solid‐phase microextraction (SPME) technique with carbowax/divinylbenzene fibers (CAR/DVB) and then analyzed by coupled gas chromatography‐mass spectrometry (GC‐MS). A series of aliphatic saturated straight‐chain n‐alkanes (n‐C23 to n‐C28), internally branched monomethylalkanes at carbons 3, 11, or 13, and dimethylalkanes were identified, which showed no qualitative differences in either sex and were similar in the samples with SPME fiber extraction and those with hexane extraction. The bioassay showed that 11‐methylpentacosane (11‐MeC25), 11‐methylhexacosane (11‐MeC26), and 11‐methylheptacosane (11‐MeC27) have sex‐specific recognition functions that triggered more mating attempts at a female‐specific ratio of 100:4:60 than at a male‐specific ratio of 100:85:50. In addition, the female‐specific ratio of 11‐methylalkanes can elicit about 70% of male mating attempts within about 60 s, whereas live females elicit about 98% of male mating attempts within 25 s. The discrepancy in the initiation of mating attempts by synthetic mixtures and live females suggests that the methyl isomers 3‐MeC25, 3‐MeC27, and/or 11,15‐diMeC27 may also be involved in the mating behavior of S. bifasciatus. These results suggest that 11‐MeC25, 11‐MeC26, and 11‐MeC27 constitute the contact sex pheromone of S. bifasciatus, with the presence or absence of 11‐MeC26 in particular playing an important role in mate recognition by males.

A Hybrid Stainless-Steel SPME Microneedle Electrode Sensor for Dual Electrochemical and GC-MS Analysis.

A mechanically robust in-tube stainless steel microneedle solid phase microextraction (SPME) platform for dual electrochemical and chromatographic detection has been demonstrated. The SPME microneedle was fabricated by layer-by-layer (LbL) in-tube coating, consisting of carbon nanotube (CNT)/cellulose nanocrystal (CNC) film layered with an electrically conductive polyaniline (PANI) hydrogel layer (PANI@CNT/CNC SPME microneedle (MN)). The PANI@CNT/CNC SPME MN showed effective analysis of caffeine by GC-MS with an LOD of 26 mg/L and excellent precision across the dynamic range. Additionally, the PANI@CNT/CNC SPME MN demonstrated a 67% increase in sensitivity compared to a commercial SPME fiber, while being highly robust for repeated use without loss in performance. For electrochemical detection, the PANI@CNT/CNC SPME MN showed excellent performance for the detection of 3-caffeoylquinic acid (3-CQA). The dynamic range and limits of detection (LOD) for 3-CQA analysis were 75-448 mg/L and 11 mg/L, respectively. The PANI@CNT/CNC SPME MN was demonstrated to accurately determine the caffeine content and 3-CQA in tea samples and dark roast coffee, respectively. The PANI@CNT/CNC SPME MN was used for semiquantitative antioxidant determination and composition analysis in kiwi fruit using electrochemistry and SPME-coupled GC-MS, respectively.

Incorporating performance reference compounds in retractable/reusable solid phase microextraction fiber for passive sampling of hydrophobic organic contaminants in water

Solid phase microextraction (SPME) has been used to measure aqueous-phase hydrophobic organic chemicals (HOCs) in equilibrium passive sampling mode for over two decades. However, determination of the extent of equilibrium has not been well-established for the retractable/reusable SPME sampler (RR-SPME), especially in the field applications. The goal of this study was to establish a method regarding to sampler preparation and data processing to characterize the extent of equilibrium of HOCs on the RR-SPME (100-μm thickness of polydimethylsiloxane (PDMS) coating) by incorporating performance reference compounds (PRCs). A fast (4 h) PRC loading protocol was identified with using a ternary solvent mixture (i.e., acetone-methanol-water mixture (4:4:2, v/v)) to accommodate diverse carrier solvents of the PRCs. The isotropy of the RR-SPME was validated by a paired, co-exposure approach with 12 different PRCs. The aging factors measured with the co-exposure method approximately equal to one, indicating the isotropic behavior was not changed after storage at 15 °C and −20 °C for 28 days. As a method demonstration, the PRC-loaded RR-SPME samplers were deployed in the ocean off Santa Barbara, CA (USA) for 35 days. The PRCs approaching the extents of equilibrium ranged from 20 ± 15.5 % to 96.5 ± 1.5 % and showed a declining trend along with log KOW increase. A generic equation relationship was deduced based on a correlation relationship of desorption rate constant (k2) and log KOW to extrapolate non-equilibrium correction factor from the PRCs to the HOCs. The merit of the present study is manifested by its theory and implement to enable the RR-SPME passive sampler to be utilized in environmental monitoring.

Comparison of Individual Sensors in the Electronic Nose for Stress Detection in Forest Stands.

Forests are increasingly exposed to natural disturbances, including drought, wildfires, pest outbreaks, and windthrow events. Due to prolonged droughts in the last years in Europe, European forest stands significantly lost vitality, and their health condition deteriorated, leading to high mortality rates, especially, but not limited to, Norway spruce. This phenomenon is growing, and new regions are being affected; thus, it is necessary to identify stress in the early stages when actions can be taken to protect the forest and living trees. Current detection methods are based on field walks by forest workers or deploying remote sensing methods for coverage of the larger territory. These methods are based on changes in spectral reflectance that can detect attacks only at an advanced stage after the significant changes in the canopy. An innovative approach appears to be a method based on odor mapping, specifically detecting chemical substances which are present in the forest stands and indicate triggering of constitutive defense of stressed trees. The bark beetle attacking a tree, for example, produces a several times higher amount of defense-related volatile organic compounds. At the same time, the bark beetle has an aggregation pheromone to attract conspecifics to overcome the tree defense by mass attack. These substances can be detected using conventional chemical methods (solid-phase microextraction fibers and cartridges), and it is proven that they are detectable by dogs. The disadvantage of classic chemical analysis methods is the long sampling time in the forest, and at the same time, the results must be analyzed in the laboratory using a gas chromatograph. A potential alternative novel device appears to be an electronic nose, which is designed to detect chemical substances online (for example, dangerous gas leaks or measure concentrations above landfills, volcanic activity, etc.). We tested the possibility of early-stage stress detection in the forest stands using an electronic nose Sniffer4D and compared the individual sensors in it for detecting the presence of attacked and dead trees. Our results indicate the promising applicability of the electronic nose for stress mapping in the forest ecosystem, and more data collection could prove this approach.

Piperazine-linked metal covalent organic framework-coated fibers for efficient electro-enhanced solid-phase microextraction of chlorophenols

Conductive covalent organic frameworks (COFs) have received considerable attention and are critical in various applications such as electro-enhanced solid-phase microextraction (EE-SPME). In this work, a novel piperazine-linked copper-doped phthalocyanine metal covalent organic framework (CuPc-MCOF) was synthesized with good stability and high electrical conductivity. The synthesized CuPc-MCOF was then used as an EE-SPME coating material for extraction of five trace chlorophenols (CPs), including 2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4,5,6-tetrachlorophenol (2,4,5,6-TCP), exhibiting excellent extraction performance because of various synergistic forces between CuPc-MCOF fibers and CPs. By combining EE-SPME with gas chromatography-tandem mass spectrometry (GC–MS/MS), a sensitive method for CPs detection was established with a low limit of detection (0.8–5 ng L−1) and good reproducibility (RSD≤8.4%, n = 3). This method was then successfully applied to the analysis of trace CPs in real samples of seawater and seafood. Results showed that the developed CuPc-MCOF coating material possessed superior extraction performance and potential application in extraction of trace polar pollutants from complex samples.

Two-Dimensional Nitrogen-Doped Carbon Nanosheets Derived from g-C3N4 /ZIF-8 for Solid-Phase Microextraction in Exhalation of Esophageal Cancer Patients

Here, two-dimensional (2D) nitrogen-doped carbon nanosheets (CNSs) were prepared through carbonizing MOFs (ZIF-8) in-situ grown using graphitic carbon nitride (g-C3N4) as a template. The developed ZIF-8 CNS was then used as solid-phase microextraction (SPME) fiber coating for beneficiation of five biomarkers in exhalation of patients with esophageal cancer and in gas chromatography-mass spectrometry (GC-MS) for determination. The ZIF-8 CNS fiber exhibits satisfactory enrichment factors (3490-5631), wide linearity (5-1000 μg L-1), and low detection limits (0.26-0.96 μg L-1). The relative standard deviations (RSDs) for six replicate extractions of the same ZIF-8 CNS fiber were between 2.0-3.9% (intra-day) and 2.8-5.2% (inter-day). The reproducibility of three fibers prepared by the same approach was in the range 6.8-12.3% (RSD). The developed ZIF-8 CNS fiber can persist in 120 SPME cycles with no prominent loss of extraction efficiency and precision. The high enrichment factors of the 2D ZIF-8 CNS coatings are attributed to the high specific surface area, ultrathin thickness, and nano-pore or interlayer channels; moreover, nitrogen doping also endows the π system with a strong electron absorption ability, which will enhance the π-π interaction between the ZIF-8 CNS and the aromatic ring. Ultimately, the self-made ZIF-8 CNS-coated SPME fiber was applied to the analysis of exhaled breath samples. The recoveries of spiked analytes are between 84 and 105%.

The Preparation of Covalent Bonding COF-TpBD Coating in Arrayed Nanopores of Stainless Steel Fiber for Solid-Phase Microextraction of Polycyclic Aromatic Hydrocarbons in Water.

Covalent organic framework (COF)-TpBD was grafted on the arrayed nanopores of stainless steel fiber (SSF) with (3-aminopropyl) triethoxysilane as the cross-linking agent. The prepared SSF bonded with COF-TpBD showed high thermal and chemical stability and excellent repeatability. The prepared SSF bonded with COF-TpBD was also used for the solid-phase microextraction (SPME) of seven kinds of polycyclic aromatic hydrocarbons (PAHs) in actual water samples, followed by gas chromatography with flame ionization detection (GC-FID) determination, which exhibited low limits of detection (LODs), good relative standard deviation (RSD) and high recoveries.

Modified Graphenized Pencil Lead by CoNi2S4 Nanostructure as a SPME Fiber for Analysis of PAHs from Water Samples

The main goal of this study is the hierarchical synthesis nanostructure CoNi2S4 on the graphenized pencil lead (GPL) and application as solid phase microextraction (SPME) fiber for determination of environmental pollutants. The synthesized nanostructure fiber was investigated by scanning electron microscope, energy dispersive X-ray, X-ray diffraction, Fourier transforms infrared spectroscopy and thermogravimetric analysis. The efficiency of the modified fiber as a new extraction phase for SPME was evaluated by the determination of polyaromatic hydrocarbons (PAHs) from river water samples. The extracted PAHs were monitored by GC-FID. The affecting parameters on the extraction process such as pH, temperature, salinity, stirring speed, and extraction time were investigated. The analytical parameters for determination of PAHs by CoNi2S4/GPL fiber were studied. Under the optimized conditions, the linearity range of calibration curve was obtained from 0.0001 to 10 µg L−1. The range of correlation coefficients (R 2) and limits of detections were resulted from 0.998 to 0.987 and 0.0001 to 0.003 µg L−1, respectively. The proposed fiber was successfully used to evaluate PAHs in spiked river samples and RSD % values were obtained in the range of 3.8 − 9.3%.

Metal organic framework/covalent organic framework composite for solid-phase microextraction of polycyclic aromatic hydrocarbons in milk samples

Based on the excellent physicochemical properties of metal organic framework (MOF) and covalent organic framework (COF), a novel MOF/COF composite was designed and prepared as coating fiber for headspace solid-phase microextraction (HS-SPME). Based on the amino group on the surface of as-synthesized UiO-66-NH2, porphyrin-based COF was covalently grown on the MOF surface by using tetra(4-aminophenyl)porphyrin and 4,4′-biphenyldicarboxaldehyde as building blocks to fabricate a novel MOF/COF composite. Subsequently, the composite was physically coated on the surface of polished stainless-steel wire for HS-SPME of polycyclic aromatic hydrocarbons (PAHs) by gas chromatography-flame ionization detection (GC-FID) determination. The morphology and structure of the MOF/COF composite was characterized by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and N2 adsorption–desorption. Influential adsorption and desorption parameters were optimized and the extraction mechanism was also discussed. Under optimal conditions, an HS-SPME/GC-FID method based on MOF/COF composite coated fiber was established for the analysis of PAHs in milk samples. The linear ranges of this method were 0.2–50.0 ng mL−1 (R2 > 0.9908), and the limits of detection and quantitation were in the range of 0.02–0.07 ng mL−1 and 0.07–0.24 ng mL−1, respectively. The relative standard deviations (RSDs) for PAHs were all less than 7.05 %, which indicated eminent repeatability and reproducibility of the established method. Besides, the enrichment factors for PAHs were relatively high in the range of 2003 to 7763, and the recoveries for milk samples were ranged from 85.43 % to 115.8 % with satisfactory RSDs of 0.92–9.00 %.

A multi-site recognition molecularly imprinted solid-phase microextraction fiber for selective enrichment of three cross-class environmental endocrine disruptors.

Molecularly imprinted solid-phase microextraction fibers with multi-site recognition were prepared for the simultaneous enrichment of three cross-class environmental endocrine disruptors (EEDs) in environmental water. The surface morphology of the multi-site recognition molecularly imprinted fibers was characterized using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and surface area and pore size analyzer. Under optimal extraction conditions, the molecularly imprinted fibers showed higher extraction capacity to bisphenol F, diethyl phthalate, and methyl paraben than non-imprinted polymer fibers and commercial fibers. Compared with commercial solid-phase microextraction fibers, the multi-site recognition molecularly imprinted fibers showed superior extraction performance at different concentrations of analytes. The selectivity study confirmed that the multi-site recognition molecularly imprinted solid-phase microextraction fibers were highly selective not only for specific template molecules but also for bisphenols, parabens, and phthalates. Furthermore, the method achieved a limit of detection of 0.003-0.02 μg L-1 for the three cross-class EEDs in environmental water samples with recoveries ranging from 75.76% to 112.69% and relative standard deviations below 11.46%. Thus, the novel MIP fibers with multi-site recognition prepared in this work have provided a promising approach in the field of specific adsorption and a strategy for the simultaneous and sensitive monitoring of multiple cross-class trace EEDs.

Rational design of ordered porous nanoparticles for selective extraction of nitrobenzene compounds

The presence of nitrobenzene compounds (NBCs) in the environment has imparted severe threats to public health. Herein, highly selective extraction of polar NBCs from aqueous samples is achieved by rational design of novel extractants. The extraction efficiencies to NBCs are much higher than other analytes (e.g., BTEX, phenols) with subtle differences in structures and molecular dimensions. This extractant (termed as PF-CROSS) was designed by constructing micropores in nanoparticles and reserving electron-donating phenolic hydroxyl groups within the hydrophobic cavities. Owing to the shielding of the phenolic hydroxyl groups from water by the hydrophobic cavities, the polar interactions and π-π electron donor-acceptor specific interactions between the NBCs and PF-CROSS presented, which were confirmed based on Fourier transform infrared (FTIR) spectroscopy, and were further demonstrated to play important roles in selective extraction of NBCs through theoretical modeling. Moreover, the steric effect provided by the micropores further enhanced the extraction selectivity. By fabricating PF-CROSS into solid-phase microextraction fibers, the detection limits of developed method reached as low as 0.32–5.39 ng L−1 for NBCs in water samples. This study provides an efficient and cost-effective extraction phase for highly sensitive detection of NBCs, which is also promising for the recycling of NBCs in the future.

A molecularly imprinted fiber array solid-phase microextraction strategy for simultaneous detection of multiple estrogens.

A kind of selective enrichment material based on a homemade molecularly imprinted polymer (MIP) fiber array with high adsorption capacity was developed for the accurate analysis of estrogens in food samples. Here, the MIP with 17β-estradiol as the template was obtained by in situ polymerization. The chemical composition, morphologies, surface area, and pore size of the polymer were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmett-Teller theory. The extraction time, desorption solvent, desorption time, ionic strength, and the pH of solution were investigated to ascertain the best extraction conditions. Under the optimal extraction conditions, three fiber coatings of 17β-estradiol MIP and commercial polyacrylate (PA) were bound to a homemade handle to assemble the fiber array, respectively. The findings showed that the three-fiber array of the MIP significantly improved the extraction capacity by 145 times compared to PA. The MIP fiber array showed high adsorption capacity for the template molecule 17β-estradiol and its structural analogues estrone, bisphenol F, bisphenol B, and bisphenol A, with enrichment factors of 99.60-133.16. A molecularly imprinted polymer solid-phase microextraction fiber array (MIP-SPME fiber array) coupled with high-performance liquid chromatography-diode array detection was used for the analysis and detection of the five estrogens in milk and yogurt samples. Satisfactory recoveries were achieved ranging from 74.75-119.41% with <9.42% relative standard deviations. The developed method for the simultaneous determination of trace estrogens in food samples exhibited a limit of detection of 0.33 μg L-1. The MIP-SPME fiber array provided an available strategy for improving the selectivity and adsorption capacity of SPME for trace target component analysis in complex matrices and increasing the sensitivity of the analytical method.

Characterising earth scent

Environmental context Everyone is familiar with the earth odour that comes from digging in the soil. We measured the chemicals comprising this odour and studied how the environment influences how much of these chemicals are released from disturbed soils. Understanding what conditions affect emission of these compounds from soils could provide new technologies for remotely assessing soil health and what people are doing to soils. Rationale Earth scent is the odour emitted from soils. This scent, primarily comprising the alcohols geosmin and 2-methylisoborneol (MIB), has not been fully characterised, but offers high potential for use as an environmental interrogation tool. Methodology We utilised our field-based, solid-phase microextraction fibre method to test the hypothesis that soil activity and soil property variation can be detected in situ by comparing biogenic volatile emissions. Results We eliminated sources of error utilising field-based sampling with these fibres, concluding that room temperature storage for up to 7 days is acceptable with minimal loss. Variation in individual fibre affinity for both compounds was higher than expected but no measured concentrations were observed to constitute outliers. Disturbance of minor soil volumes led to significantly higher emission of both compounds over background levels. Soil texture and soil cover had a significant effect on the emission of both compounds. Simulated rainfall, producing the characteristic odour known as petrichor, initiates elevated emission of geosmin. Background (undisturbed soil) concentrations of MIB were occasionally detectable during some sampling events, but geosmin concentrations in the air were always below detection limits without soil disturbance. Virtually all background and disturbed soil samples contained much higher concentrations of MIB compared to geosmin, but geosmin variation between replicates and experimental units was much lower. Discussion Soil disturbance and soil property variation can be remotely detected using emission of volatile compounds. Correlating emission from the soil with respect to disturbance events and environmental properties could yield a powerful new tool for acquiring soil information.

A Facile and in situ Preparation Technique for Solid-Phase Microextraction Fibers with MOFs Coating

In this study, a facile preparation technique for in situ growth of MOFs-based-coated solid-phase microextraction (SPME) fibers is proposed. NH2-MIL-53 can be grown on the Al wire simply by immersing the Al wire in the solution of growth seeds and metal–organic frameworks (MOFs) successively, thereby obtaining the SPME fiber. The as-prepared fiber was combined with gas chromatography flame ionization detection (GC-FID) for the determination of non-steroidal anti-inflammatory drugs (NSAIDs) in water samples. Compared with NH2-MIL-53-coated fiber prepared with the gluing method, MIL-53-coated fiber prepared by in situ self-growth and commercial polyacrylate (PA) fiber, the as-prepared fiber demonstrated the better extraction performance, owing to more exposed adsorption sites and stronger interactions with the target. Moreover, the fiber exhibited a long service life due to multifaceted stability. After optimization of extraction and desorption conditions, the analytical method had a low-detection limit (0.002–0.05[Formula: see text][Formula: see text]g[Formula: see text]L[Formula: see text], a wide linear range (0.01–500[Formula: see text][Formula: see text]g[Formula: see text]L[Formula: see text] and good reproducibility (relative standard deviation [Formula: see text]5.84%) and provided good results for actual water samples. MOFs-based SPME fibers grown on metal wires using a facile in situ technique can maximize the extraction advantage of MOFs coating, which well promotes the application and development of MOFs in solid-phase microextraction technology.

Standard Water Generating Vials for Lipophilic Compounds

The study of non-polar compounds in aqueous environments has always been challenging due to their poor solubility in aqueous media. The low affinity of non-polar compounds toward polar solutions facilitates their attachment to glassware, which results in unstable sample concentrations. To address this challenge, and to enable the preparation of a stable mixture of hydrophobic compounds in an aquatic environment, we introduce an in-vial standard water generating system consisting of a vial containing appropriate aqueous solution and a polydimethylsiloxane thin film spiked with target compounds. In this system, a solution with a stable analyte concentration is attained once equilibrium between the thin-film and aqueous solution has been achieved. The developed standard water system was studied using endocannabinoids and phospholipids as model hydrophobic compounds of biological importance, with results indicating that the concentration of hydrophobic compounds in water can remain stable over multiple days. The results also showed that analytes released from the thin film can compensate for analyte loss due to extractions with solid-phase microextraction fibers, thereby re-establishing equilibrium. Thus, the vial is suitable for the repeatable generation of non-polar standards for routine analysis and quality control. The results of this work show that the developed system is stable and reproducible and therefore appropriate for studies requiring the measurement of free concentrations and accurate quantification.

Predicting the bioavailability of nitro polycyclic aromatic hydrocarbons in sediments: ZIF-8/h-BN solid-phase microextraction versus Tenax extraction

The occurrence of nitrated polycyclic aromatic hydrocarbons (NPAHs) in sediments has been widely reported, but research on NPAH bioavailability is lacking. In this study, a self-made zeolite imidazolate framework-8/hexagonal boron nitride (ZIF-8/h-BN) solid-phase microextraction (SPME) fiber and commercial Tenax are compared as efficient tools to predict the bioavailability of NPAHs in sediments with bioassays using Cipangopaludina chinensis. During the process of SPME, the NPAH concentrations on the ZIF-8/h-BN fibers reached extraction equilibrium after 72 h. The fiber extraction of NPAHs in sediments was well-fitted by the pseudo first-order kinetic model with a rate constant of 2 × 10−2 h−1 (R2 > 0.98). The extraction rates ranking of NPAHs in sediments was 2-nitrobiphenyl>1-nitropyrene>5-nitroacenaphthene>2-nitrofluorene. Compared with SPME, NPAH concentrations reached equilibrium after 168 h for the Tenax extraction. The orders of magnitude of fast, slow, and very slow desorption rate constants were 10−1, 10−2, and 10−4, respectively. At extraction equilibrium (168 h), the SPME was close to the bioavailability of the NPAHs in sediments to Cipangopaludina chinensis with a slope statistically approximated to one. In addition, the linear regression for SPME (R2 = 0.7285) was slightly higher than that of the Tenax extraction (R2 = 0.7168) over a short time (6 h). This could be because the coating material of ZIF-8/h-BN can rapidly adsorb freely dissolved NPAHs, and the SPME fibers can accurately predict the bioaccumulated concentrations of NPAHs in exposed organisms by measuring the concentration of NPAHs in the pore water of sediment. This study provides a time-saving and easy procedure to predict the bioavailability of NPAHs in sediments.

Carbonized MXene-polyvinylpyrrolidone as an adsorbent for solid-phase microextraction of polycyclic aromatic hydrocarbons from tea beverages prior to GC analysis

MXene-polyvinylpyrrolidone (MXene-PVP) was first prepared by physically doping combined with spray drying, which can overcome the aggregation of the MXene. Then, the MXene-PVP was carbonized to result in a carbonized MXene-PVP (MXene-PVP-C), which was then immobilized on stainless steel wire by sol–gel approach to prepare a new solid-phase microextraction (SPME) fiber. The prepared MXene-PVP-C coated fiber was studied for the extraction of 10 polycyclic aromatic hydrocarbons (PAHs) from tea beverages by using SPME method prior to gas chromatographic detection. The main SPME parameters, including extraction temperature, extraction time, salt concentration, sample solution pH and stirring rate, were investigated by central composite design methodology. Under the optimized conditions, the developed method gave the limits of detection of 0.03–0.15 µg/L, and the limits of quantification of 0.10–0.50 µg/L for the PAHs. The method recoveries for the PAHs in spiked tea beverages ranged from 78.6 % to 122 %. The single-fiber and fiber-to-fiber relative standard deviations were lower than 8.2 % and 9.6 %, respectively.

Unraveling the impact of the capsule material on the aroma of brewed coffee by headspace analysis using a HiSorb probe followed by reverse fill/flush flow modulation GC×GC-MS.

The present paper discusses the use of a high-concentration-capacity tool, HiSorb, to investigate the impact of capsule material on the aroma profile of espresso-brewed coffee. The specific high-concentration-capacity probe used is characterized by a sorbent volume (63 μL) intermediate between the solid-phase microextraction (SPME) fiber (0.6 μL) and the stir-bar sorptive extraction rod (126 μL). The extraction performance of the HiSorb was compared, in terms of both absolute signal and compound coverage, with both an equivalent sorbent (polydimethylsiloxane) and a divinylbenzene/carboxen/polydimethylsiloxane SPME fiber using both targeted and untargeted approaches. The HiSorb showed superior extraction compared with the SPME fibers. The HiSorb was then optimized in terms of extraction time and temperature and used to investigate the volatile profile of 23 espresso-brewed coffees prepared with capsules made of different materials-aluminum, compostable, and aluminum multilayer pack-prepared using a refillable capsule. Comprehensive two-dimensional gas chromatography equipped with a reverse fill/flush flow modulator and coupled to mass spectrometry was used to obtain a chromatographic fingerprint of the volatile profile of the brewed coffee. The data were aligned and compared using a tile-based approach, and the results were obtained by performing raw data mining within the same software platform. The data mining enabled the extraction of informative features responsible for the differentiation between the different capsule materials, showing a significant depletion in aroma intensity in the compostable capsule.

At-Line Sampling and Characterization of Pyrolytic Vapors from Biomass Feedstock Blends Using SPME-GC/MS-PCA: Influence of Char on Fast Pyrolysis.

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) analysis was used for the at-line sampling of pyrolytic vapors produced during the fast pyrolysis of biomass. The pure and binary blends of switchgrass (SWG) and pine harvest residues (PT6) were used as biomass feedstocks. Sequential SPME sampling allowed for monitoring of changes in the pyrolysis vapors as char accumulated in the fluid bed. The relative concentration and composition of the pyrolysis vapors desorbed from the SPME fibers were investigated using GC-MS, and the resulting chromatograms were analyzed using principal component analysis (PCA) to compare the composition of the pyrolysis vapors over the course of the pyrolysis run. The chemical compositions of both carbohydrate and lignin fragments varied as the char builds up in the reactor bed. Fragments derived from cellulose and hemicelluloses included anhydrosugars, furans, and light-oxygenated compounds. Lignin fragments included methoxyphenols, phenolic ketones, aldehydes, and low-molecular-weight aromatics. The composition of the carbohydrate fragments changed more than those of the lignin fragments as the char built up in the fluid bed. This combination of SPME-GC/MS-PCA was a novel, easy, and effective method for measuring the composition and changes in the composition of pyrolysis vapors during the fast pyrolysis process. This work also highlighted the effect of char build-up on the composition of the overall pyrolysis vapors.