Search

The application of distributed fiber optic strain and temperature measurement can be utilized to address a multitude of measurement tasks across a diverse range of fields, particularly in the context of structural health monitoring in the domains of building construction, civil engineering, and special foundation engineering. However, a comprehensive understanding of the influences on the measurement method and the sensors is essential to prevent misinterpretations or measurement deviations. In this context, this study investigated the effects of moisture exposure, including various salt solutions and a high pH value, on a distributed strain measurement using Rayleigh backscattering. Three fiber optic sensors with different coating materials and one uncoated fiber were exposed to five different solutions for 24 h. The study revealed significant discrepancies (∼38%) in deformation between the three coating types depending on the surrounding solution. Furthermore, in contrast to the prevailing literature, which predominantly describes swelling effects, a negative deformation (∼-47 με) was observed in a magnesium chloride solution. The findings of this study indicate that corresponding effects can impact the precision of measurement, potentially leading to misinterpretations. Conversely, these effects could be used to conduct large-scale monitoring of chemical components using distributed fiber optic sensing.

There is an urgent need to develop efficient and reliable coating materials for solid phase microextraction (SPME), in order to quantify and monitor pollutants in environmental waters. Herein, a highly graphitized porous carbon/reduced graphene oxide (PC/rGO) was successfully synthesized by pyrolysis of metal organic framework/graphene oxide precursors, and used as a SPME coating for ultrahigh enrichment of polycyclic aromatic hydrocarbons (PAHs) from water. The as-prepared PC/rGO exhibited high degree of graphitization, abundant number of micro/mesopores along with exceptional thermal stability, making it an ideal SPME coating material. The PC/rGO fiber offered an ultrahigh enrichment factor for PAHs (up to 126057), which could be attributed to the multiple interactions between the PC/rGO and PAHs, including hydrophobic and π-π interactions, partitioning, and mesopore filling effect. In the analysis of PAHs, the PC/rGO fiber showed a wide linearity (0.007-100 ng mL -1 ), low limits of detection (0.0005-0.005 ng mL -1 ), and good repeatability (RSDs <10.1%, n = 5) under optimized conditions. The established method was applicable for ultrasensitive determination of PAHs in different environmental waters and showed satisfactory recoveries. This study provides a novel way for constructing thermally stable SPME coating having efficient extraction performance., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Developing functional fiber coating for selective solid phase microextraction (SPME) of trace pollutants is critical in environmental analysis. Herein, the novel covalent organic frameworks (COFs) with three-dimensional (3D) frameworks and multiple interactions were designed and presented for the selective SPME of polychlorinated biphenyls (PCBs). Using tetra (p-aminophenyl) methane (TAM) and 1,3,5-triformylphloroglucinol (Tp) as the monomers, the 3D TpTAM-COF was synthesized and possessed a large specific surface area, high thermal stability, and spatial selectivity toward PCBs. Characterizations such as morphology, XPS, XRD, thermal stability, and enhancement factors (EFs) were studied. Multiple interactions including π-π conjugation, hydrophobic interaction, and selectivity toward non-planar structure were adopted, which resulted in a superior adsorption affinity toward PCBs on TpTAM-COF. Under the optimal conditions, the spatial selectivity toward PCBs, organic analogs (o-dichlorobenzene, biphenyl) and polycyclic aromatic hydrocarbons (naphthalene, pyrene, and anthracene)) was achieved. Efficient and selective adsorption of fifteen PCBs was fulfilled with the highest EF up to 10305. Using the HS-SPME-GC-MS method, the recoveries of PCBs in the river water and soil samples were determined to be 84.8 ± 7.8% ∼ 117.2 ± 8.5% (n = 3) and 84.4 ± 8.6% ∼ 114.7 ± 7.6% (n = 3), respectively. Compared with most commercial SPME fibers and other COFs-based fibers, the resultant TpTAM-COF-coated fibers possessed higher selectivity and EFs of PCBs. It proposed a promising approach for selective SPME of trace PCBs by multiple interactions in the steric structure of 3D COFs., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest. We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Efficient and selective solid-phase microextraction of polychlorinated biphenyls by using a three-dimensional covalent organic framework as functional coating”., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Owing to the severe toxicity and health hazard of polychlorinated biphenyls (PCBs) to humans, the efficient separation and determination of PCBs in dairy products is highly desirable and challenging. In this study, a new solid-phase microextraction (SPME) fiber was prepared by coating of a new molecularly imprinted phenolic resin (MIPR) in situ using a covalent grafting method. The MIPR coating, synthesized from 4-mercaptophenol and glutaraldehyde, provides rough surface with more adsorption sites; furthermore, the coating has a thickness of 1.0 μm, resulting in rapid equilibration. This new device has the advantages such as less coating peeling from the substrate and selective recognition enhancement of the coating. A highly selective and sensitive SPME-based method was developed using the developed fiber, coupled with GC-MS/MS, for the determination of polychlorinated biphenyls (PCBs) in milk samples. The developed MIPR-HS-SPME-GC-MS/MS method showed low detection limits (0.012-0.066 pg mL -1 ), good linearity (r ≥ 0.9991), satisfactory recovery (77.5-116.7%), efficient enhancement factors (362-2034 folds) and good reusability (50 cycles). Therefore, this is a simple and efficient strategy for monitoring trace PCBs in complex samples and is a potential alternative for improving the selectivity of SPME fibers by introducing MIPR into the fiber coating., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Fiber coating is a key part of solid-phase microextraction (SPME) technology, and it determines the selectivity, sensitivity, and reproducibility of the analytical method. A ketoenamine covalent organic framework called Tp-Azo-COF with rich electronegative N atoms was prepared as an SPME coating in this work. The Tp-Azo-COF coating had a large surface area of 1218 m 2 g -1 and good thermal and chemical stability, and it was applied for the extraction of organochlorine pesticides (OCPs). According to quantum chemistry calculations, the adsorption affinity of the Tp-Azo-COF coating for five OCPs was primarily affected by the halogen bond and hydrophobicity interaction. The extraction efficiencies of the Tp-Azo-COF coating for five OCPs were higher than those of three commercial SPME fiber coatings, and the enrichment factors ranged from 1061 to 3693. When combined with gas chromatography-tandem mass spectrometry, a wide linear range (0.1-1000 ng L -1 ), low limits of detection (0.002-0.08 ng L -1 ), and good fiber-to-fiber accuracy (4.3-10.9%) were achieved under optimal conditions. Moreover, the applicability of the developed method was evaluated by analyzing four samples (milk, green tea, tap water, and well water), and the recoveries were in the range of 83.4-101.6%, with relative standard deviations <8.6%. This research extends the application of the stabilized ketoenamine COF as a sample enrichment probe for OCP analysis.

Diffusion of the analytes across the diffusion boundary layers and subsequently through the fiber coatings determines the extraction kinetics of solid-phase microextraction in aqueous matrices. Besides, the matrix effects can distort the behaviors of the analytes transferring across the diffusion boundary layers. However, these processes were always studied via certain simplification, which often left the mass transfer through the fiber coatings unconsidered and the matrix effects partially investigated. Herein, a comprehensive study on the mass transfer processes in direct immersion solid-phase microextraction was presented. Under different agitation speeds, it was determined that the mass transfer coefficients across the diffusion boundary layers were three to six orders larger than those through the fiber coatings. However, the mass transfer across the diffusion boundary layers was generally the major rate-limiting step. In addition, the shuttle effect and the barrier effect, which were responsible for accelerating and retarding the extraction kinetics, respectively, were found to be the dominant matrix effect alternately under different agitation speeds. This study comprehensively illustrated the major rate-limiting step and the dominant matrix effects through recording the mass transfer coefficients., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An amino-functionalized ordered mesoporous polymer (OMP-NH 2 ) was synthesized and applied as a fiber coating for solid phase microextraction of polar phenols from environmental samples. The fiber coating was prepared by loading the OMP-NH 2 powder onto a stainless steel wire through silicone gel. Combined with GC-MS, the fibers were employed to quantify trace of phenols in water through headspace-SPME. The characterization showed the OMP-NH 2 to have a large specific surface area (420 m 2  g -1 ) and good thermal stability (>400 °C). Due to its mesoporous structure and favorable interactions via hydrogen bonding and π stacking interactions with phenols, the sorbent represents a promising candidate for the separation and enrichment of polar phenols. Extraction conditions, such as temperature, extraction time, salt concentration, pH value and desorption time, were fully optimized. Under the optimized conditions, the coating exhibits an enrichment effect that is ~2-10 times better than that of a commercial polyacrylate coating. Figures of merit include (a) low limits of detection (0.05-0.16 ng L -1 ), (b) wide linear ranges (0.2-10,000 ng L -1 ), and (c) high enrichment factors (510-2272). The relative standard deviations for one fiber and fiber-to-fiber were in the range of 4.0-6.1% and 4.6-7.4%, respectively. The method was applied to the determination of phenols in water samples and gave satisfactory recoveries between 85.4 and 112.2%. Graphical abstract An amino-functionalized ordered mesoporous polymer (OMP-NH 2 ) was synthesized by a solventless method and applied as headspace solid phase microextraction (HS-SPME) fiber coating for the extraction of polar phenols from the environmental samples.

Fibers are an important form of forensic evidence, but their evidential value can be severely limited when the identified characteristics of the fibers are common, such as blue cotton. Detecting chemical fiber treatments offers an avenue to further classify fibers and to improve their evidential value. In this report, we investigate the potential of fluoropolymer fiber coatings, used to impart oil and water-repellent properties in fabrics, for differentiating between fibers. The thin nature of these fiber surface modifications creates an analytical challenge for their detection on a single fiber, a typical sample size for forensic evidence. Specifically, pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) has shown promising selectivity but the sensitivity of the method is not adequate for single-fiber analysis of fluorinated coatings. To overcome this challenge, we utilize a newly developed elemental ionization source, plasma-assisted reaction chemical ionization (PARCI). The high sensitivity of py-GC-PARCI-MS for elemental fluorine analysis offers selective and sensitive detection of fluorinated pyrolysates among the non-fluorinated pyrolysates of the fiber core. As a result, fluoropolymer coatings are detected from 10-mm single-fiber samples. The technique is applied for classification of 22 fiber types, resulting in 4 distinct groups via hierarchical cluster analysis based on similarity of fluorine pyrograms. These results present the first study to classify fibers based on fluorinated coatings, and highlight the potential of py-GC-PARCI-MS for forensic analyses. Graphical Abstract ᅟ.

In spite of the effectiveness of the fiber coatings on interface modification of carbon fiber reinforced magnesium matrix composites, the cost and exclusive equipment for the coatings preparation are usually ignored during research work. In this paper, pyrolytic carbon (PyC) and TiO 2 were coated on carbon fiber surface to study the effects of fiber coatings on interfacial microstructure and mechanical properties of carbon fiber reinforced AZ91D composites (C f /AZ91D composites). It was indicated that both the two coatings could modify the interface and improve the mechanical properties of the composites. The ultimate tensile strength of the TiO 2 -C f /AZ91D and the PyC-C f /AZ91D composite were 333MPa and 400MPa, which were improved by 41.7% and 70.2% respectively, compared with the untreated-C f /AZ91D composite. The microstructure observation revealed that the strengthening of the composites relied on fiber integrity and moderate interfacial bonding. MgO nano-particles were generated at the interface due to the reaction of TiO 2 with Mg in the TiO 2 -C f /AZ91D composite. The volume expansion resulting from the reaction let to disordered intergranular films and crystal defects at the interface. The fibers were protected and the interfacial reaction was restrained by PyC coating in the PyC-C f /AZ91D composite. The principle to select the coating of fiber was proposed by comparing the effectiveness and cost of the coatings., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A metal organic framework-polyaniline (MOF/PANI) nanocomposite was electrodeposited on a stainless steel wire and used as a solid phase microextraction (SPME) fiber coating. The electropolymerization process was carried out under a constant deposition potential and applied to the corresponding aqueous electrolyte containing aniline and MOF particles. The employment of MOFs with their large and small cages and 3-D structures in synthesizing a nanocomposite was assumed to be efficient constitutes to induce more non-smooth and porous structures, approved by scanning electron microscopy (SEM) images. Three different MOFs were incorporated to synthesize the desired nanocomposites and the preliminary experiments showed that all of them, particularly the one containing MOF2, have higher extraction performances in compared with PANI. The applicability of the new fiber coating was examined by headspace-solid phase microextraction (HS-SPME) of some chlorobenzenes (CBs) from aqueous samples. Influencing parameters on the synthesize and extraction processes including the electrodeposition voltage and its duration time, the weight ratio of PANI and MOF, the ionic strength, desorption temperature and time, and extraction time and temperature were optimized. The developed method was validated by analyzing the spiked distilled water and gas chromatography-mass spectrometry (GC-MS). Under optimum condition, the relative standard deviation (RSD%) values for a double distilled water spiked with the selected CBs at 20ngL(-1) were 5-8% (n=3) and the detection limits were below 0.2ngL(-1). The linear dynamic range (LDR) of the method was in the concentration range of 0.5-1000ngL(-1) (R(2)>0.9994). The fiber-to-fiber reproducibility was found to be in the range of 4-7%. Eventually, various real-water samples were analyzed by the MOF/PANI-based HS-SPME and GC-MS and the relative recovery values were found to be in the range of 92-98%., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A fast and robust method was developed for the determination of ten triazole fungicides in fruit samples using direct immersion solid-phase microextraction coupled to gas chromatography with time-of-flight mass spectrometry detection (DI-SPME-GC-ToFMS). In this work, a newly developed concept of solid-phase microextraction (SPME) sorbent, which allows for direct immersion extraction in complex food matrices, has been applied in the analysis of 10 triazole fungicides in grapes and strawberries pulps. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction temperature, sample pH, and ionic strength, agitation speed, extraction and desorption times. Under optimized conditions, the method was linear for over 4 orders of magnitude in concentration, with linear regression coefficients (R(2)) greater than 0.99 for all test compounds in both matrices. Method reproducibility, as determined by analysis of spiked grapes and strawberries, was better than ±20%. The limits of quantitation objective (LOQs) ranged from 0.25 to 5 ng g(-1) for both matrices, well below the maximum residues levels allowed for those compounds in both matrices. The method was successfully applied in the analysis of commercial samples of grapes and strawberries. Finally, the new SPME method was compared to a modified version of t QuEChERS AOAC method: the limits of quantitation reached by SPME were at least one order of magnitude lower than those achieved by the QuEChERS method, whereas precision and accuracy were comparable for both methods., (Copyright © 2013 Elsevier B.V. All rights reserved.)