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The photoluminescent (PL) properties of lanthanide metal-organic frameworks (Ln-MOFs) are intrinsically subtle to water molecules, which remains the major challenge that severely limits their applications as fluorescent probes in aqueous samples. Herein novel composite fluorescent probes were prepared by growing Ln-MOFs (Tb-MOF, Eu-MOF, and Tb/Eu-MOF) on carboxylated porous graphene oxide (PGO-COOH). The 3D thorny composites presented significantly longer fluorescent lifetimes and higher quantum yields than that of the bare Ln-MOFs and exhibited long-term PL stabilities in aqueous samples up to 15 days. The stable and improved PL properties demonstrated that the highly hybrid composite structures protected the MOF components from the adverse effects of water. Furthermore, the unexpected antenna effect of the PGO-COOH substrate on Ln3+ was supposed to be another reason for the improved PL properties. The composites present ultralow detection limits as low as 5.6 nM for 2,4-dinitrotoluene and 2.3 nM for dipicolinic acid as turn-off and ratiometric fluorescent probes, respectively, which was attributed to the incoporation of PGO-COOH that dramatically enahnced inner filter effects and effectively protected the energy transfer process in the MOF components from the interference of the surrounding water. This work presents an effective strategy for creating ultrasensitive and stable fluorescent probes based on Ln-MOFs for applications in aqueous samples.

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.

In this contribution, low-cost and robust biochar material fabricated from waste peanut shells manifest highly-efficient adsorption capability and was prepared into a solid-phase microextraction fiber coating on the external surface of a stainless-steel wire. It was observed from scanning electron microscopy that, a homogeneity of cavities makes up the external surface of the coating, and Raman signals revealed that it contained graphite structures. Coupled with gas chromatography-mass spectrometry (GC-MS), headspace SPME (HS-SPME) based on the novel fiber was applied for the analysis of six polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. Under the selected optimum conditions in both extraction and desorption processes, satisfactory analytical performances were achieved, which included good intra-fiber repeatability (relative standard deviations, RSDs in the range from 6.93% to 10.86%, n = 6) and inter-fiber reproducibility (RSDs from 5.61% to 13.59%, n = 4), together with low limits of detection (LODs, 1.09–2.46 ng L−1) and limits of quantification (LOQs, 3.62–8.20 ng L−1), as well as a satisfactory linear range for the analysis of the target PAHs (10–2000 ng L−1). This established method also showed good reliability in the analysis of target PAHs in river water as well as pond water in the downtown area of Guangzhou, China, as the spiked recoveries were in the range from 81% to 116%.

Herein, a new strategy to increase the sensitivity of a lanthanide metal-organic framework (Ln-MOF) to UO22+ was proposed by using polymeric ligands. By utilizing [Tb(1,3,5-benzenetrisbenzoate)]n (Tb-TBT) MOF as the host, preloaded 2-vinyl terephthalic acid (VTP) was polymerized in situ, which produced a novel fluorescent composite denoted as PVTP⊂Tb-TBT. Benefiting from the coordination of PVTP to the Tb nodes, the polymeric chains performed both as molecular scaffolds that improved the water stability of the framework and as additional antennae that sensitized the photoluminescence of the Tb nodes. More importantly, the detection sensitivity and selectivity of PVTP⊂Tb-TBT to UO22+ were much improved compared to those of Tb-TBT. Detailed characterizations indicated that the incorporation of PVTP efficiently enriched UO22+ in the probe, which promoted the energy dissipation to UO22+. Besides, UO22+ was also supposed to release PVTP from PVTP⊂Tb-TBT and, thus, exposed the open metal sites to water molecules, which interrupted the sensitization effect of PVTP and induced a nonradiative energy dissipation. A limit of detection (LOD) as low as 0.75 nm was recorded by suspending the PVTP⊂Tb-TBT probe in a water sample, far below the limit in drinking water set by the United States Environmental Protection Agency (130 nm). Furthermore, a remotely controlled sampling and an on-site analysis of real water samples were realized by facilely loading PVTP⊂Tb-TBT on thin films (TFs). The LOD for UO22+ was 2.5 nm by using the TFs. This study reports a new strategy for boosting the sensitivity and selectivity of Ln-MOF to monitor UO22+ and expands the application of the strategy to an on-site analysis.

Recent works of designing excellent adsorbents emphasized on the specific surface areas and porosities of the materials. This study presents the influence of morphological modulation on extraction efficiencies of materials for the first time. Sea urchin-like nanoporous carbon (NPC), derived from metal organic framework (MOF), was synthesized and fabricated as solid phase microextraction (SPME) device. The morphological modulated structure of the NPC, with enhanced effective adsorption sites produced by the pointed and sharp edges, could improve the extraction efficiencies of the NPC. Comparing with the unmodulated one, NPC with morphological modulation possessed higher extraction efficiencies (2 flod) as well as accelerated sampling rates (5 flod) on benzene series compounds (BTEX), improving the sensitivity of the sampling method (limits of detection ranged from 0.08 ng L−1 to 0.36 ng L−1). Moreover, it was also the first time that the moisture sensitive MOF-derived NPC was exploited as the SPME adsorbent. In general, this study was expected to be an important advance in broadening the approaches on designing a superior SPME adsorbents not only emphasizing on the specific surface area as well as porosity but also the morphology.

3D graphene-carbon nanotubes (G-CNTs) composite with unique morphology and structure was prepared by one-step insertion of CNTs into graphene. Subsequently, the G-CNTs composite as a fiber coating material for solid-phase microextraction (SPME) was fabricated on the surface of a stainless steel wire by direct coating method. The prepared coating was tested by the extraction of benzene homologues (BTEX, benzene, toluene, ethylbenzene and m-xylene). Compared with a commercial polydimethylsiloxane (PDMS) fiber, the home-made coating exhibited higher extraction performance for BTEX, and the reasons were discussed systematically. Under the optimized conditions, the prepared coating coupled with chromatography-mass spectrometry (GC–MS) for the analysis of BTEX exhibited wide linear ranges, low limits of detection (3 S/N) (LODs, 0.59–2.68 ng L−1), low limits of quantification (10 S/N) (LOQs, 1.96–8.92 ng L−1), good repeatability (3.2–5.5%, n = 6) and reproducibility (3.7–9.1%, n = 3). Finally, the developed method was successfully applied to the analysis of BTEX in environmental water samples with satisfactory recoveries (84.7–108.1%). This study is expected to further the exploration of high-performance SPME coating materials, and broaden the applications of graphene-based materials.

Adsorption capacity is the major sensitivity-limited factor in solid-phase microextraction. Due to its light-weight properties, large specific surface area and high porosity, especially tunable pore structures, the utilization of porous organic polymers as solid-phase microextraction adsorbents has attracting researchers' attentions. However, these works mostly concentrated on the utilization of specific porous organic polymers for preparing high-performance solid-phase microextraction coatings. The relationship between pore structures and adsorption performance of the porous organic polymers still remain unclear. Herein, three porous organic polymers with similar properties but different pore distributions were prepared by condensation polymerization reaction of phloroglucinol and terephthalaldehyde, which were fabricated as solid-phase microextraction coatings subsequently. The adsorption capacity of the porous organic polymers-coated fibers were evaluated by using benzene and its derivatives (i.e.,benzene, toluene, ethylbenzene and m -xylene) and polycyclic aromatic hydrocarbons as the target analytes. The results showed that the different adsorption performance of these porous organic polymers was mainly caused by their different pore volumes instead of their surface areas or pore sizes. Finally, the proposed method by using the mesoporous organic polymer coating was successfully applied to the determination of benzene and its derivatives in environmental water samples. As for analytical performance, high pre-concentration factors (74–2984), satisfactory relative recoveries (94.5 ± 18.5–116.9 ± 12.5%), intraday precision (2.44–5.34%), inter-day precision (4.62–7.02%), low limit of detections (LODs, 0.10–0.29 ng L −1 ) and limit of quantifications (LOQs, 0.33–0.96 ng L −1 ) were achieved under the optimal conditions. This study provides an important idea in the rational design of porous organic polymers for solid-phase microextraction or other adsorption applications.

Polyaniline/silver (PANI/Ag) composites were prepared with a one-step synthesis method, and fabricated into solid-phase microextraction fiber coatings through three different means, i.e. in situ growth, gluing and chemical bonding. This work explored the utility of the as-fabricated PANI/Ag SPME fibers as dual-functional platforms for microextraction and matrix-free laser desorption/ionization (LDI) of the target analyte. The results showed that after incorporating Ag into the PANI polymer, the LDI efficiency was improved by over two times, which was 92.8% the LDI efficiency of the commercial LDI plate. In addition, the in situ grown fiber coatings were observed the most sensitive as dual platforms for the analysis of bifenthrin. The signal intensity was increased over twenty times by using in situ grown fiber, comparing to direct analysis with commercial LDI plate, which were attributed to the excellent extraction ability of PANI backbone, as well as the high LDI efficiency of the PANI/Ag composites. Low detection limit (lower than 10ngL-1) and good fiber-to-fiber repeatability (relative standard deviation 11.0%, n=3) were obtained by using the in situ grown coating for the analysis of bifenthrin, and bifenthrin in real water samples was successfully analyzed. The work successfully coupled SPME with matrix-free LDI, which greatly simplified the analytical process and improved the analytical sensitivity.

Tetrodotoxin (TTX) is one of the most toxic substances of non-protein in nature. In present study, a rapid and sensitive method based on in vivo solid-phase microextraction (SPME) coupled to liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed to detect the endogenous TTX in pufferfish (Fugu). Fiber evaluation experiments demonstrated that, compared with the commercial PDMS and PA fibers, the home-made electrospun PS@PDA-GA fibers exhibited much better extraction performance towards to TTX in water (120 times and 20 times, respectively), under the optimized conditions. Then, the home-made SPME fibers were employed to extract TTX in spiked homogeneous fish muscle samples, and a LC-MS-MS was used for the analysis. The reproducibilities (RSDs of inter and intra fiber were 12.1%, and 7.9% respectively), linear range (10-1000ngg-1, R2=0.9963) and sensitivity (the LOD was 2.3ngg-1) of the method were found to be excellent and satisfactory for further in vivo experiments. Especially the LOD of the established method is lower than the National Standard Method of China (GB/T 23217-2008, LOD 50ngg-1). Subsequently, the method was successfully applied to detect the TTX in the dorsal muscle of living pufferfish, and the accuracy was verified with traditional liquid extraction (LE) method. In general, this is the first study to detect TTX in pufferfish by in vivo sampling method, which provided a promising alternative method for the studies of TTX, and also advanced the implementation of SPME for more in vivo studies.

In this contribution, it was discovered that even distribution of a metal-organic framework (MOF) [e.g. copper 1,4-benzenedicarboxylate (CBDC)] within polymeric matrixes (e.g. polyimide) resulted in a high-efficient coating material on the surface of a stainless steel wire (SSW). Consequently, a home-made solid phase microextraction (SPME) fiber was fabricated for fast determination of target analytes in real water samples. Scanning electron microscope images indicated that the coating possessed homogenously porous surface. Coupled with gas chromatography-mass spectrometry (GC-MS) and direct immersion SPME (DI-SPME) technique, the fiber was evaluated through the analysis of five polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. Under optimized extraction and desorption conditions, the established method based on the home-made fiber exhibited good repeatability (4.2–12.7%, n = 6) and reproducibility (0.9–11.7%, n = 3), low limits of detection (LODs, 0.11–2.10 ng L−1), low limits of quantification (LOQs, 0.36–6.99 ng L−1) and wide linear ranges (20–5000 ng L−1). Eventually, the method was proven applicable in the determination of PAHs in real samples, as the recoveries were in a satisfactory range (81.7–116%).

The concentration of five rapidly metabolized anesthetics in living tilapias was determined in this study, by the presented method coupling in vivo solid phase microextraction (SPME) to gas chromatography-mass spectrometry (GC-MS), which was the first time that in vivo sampling method was adapted in detecting the anesthetic residue in the living aquatic product. The analytical performance of the developed method was evaluated in homogenized tilapia dorsal muscle, and the results demonstrated that the present method possessed low detection limits 1.7–9.4 ng g −1 ), wide linear ranges (10 or 30–5000 ng g −1 ), and satisfactory reproducibility (relative standard deviations no more than 8.1% and 10.8% for inter-fiber and intra-fiber assays, respectively). Standard curves were established in homogenized tilapia dorsal muscle for calibrating in vivo SPME in living tilapias. And the concentrations determined by in vivo SPME were close to those determined by the liquid extraction. By using the present method, one anesthetic residue was detected above the detection limit in tilapias from the local markets. Comparing to traditional methods, the present one exhibited superior time-efficiency and cost performance, as the extraction time was only ten minutes, which was short to successfully avoid the possible loss of analytes caused by elimination and sample storage. In addition, owing to the time-efficiency of the present method, the elimination of the anesthetics in tilapias was traced successfully in the laboratory.

A novel disposable styrene based solid-phase microextraction (SPME) fiber was synthesized for the detection of lipid-lowering and antihypertensive drugs in real aquatic environment. Styrene and poly(ethylene glycol) diacrylate were co-polymerized on quartz fibers by thermal polymerization in capillary molds. The polymeric fiber possessed a homogeneous, dense as well as porous surface, showing excellent chemical and mechanical stability. The performance of the fiber was evaluated through the extraction of seven pharmaceuticals by coupling SPME with high performance liquid chromatography-tandem mass spectrometry under the optimized extraction conditions. The extraction efficiency of the fiber was up to 278 times of PDMS fiber and the enrichment factors ranged from 55 to 1183. The limits of detection were in the range from 1.7 ng L−1 to 11.7 ng L−1, with good reproducibility. Moreover, the fiber was used in the real water samples of the Pearl River Delta. The recoveries of the target analytes from river water and sea water samples at different spiked concentrations were in the range from 84.1% to 133.4% and from 81.5% to 105.5%, respectively.

The development of carbon sorbents with high specific surface areas remains a hot research field in analytical community. In the current study, a novel three-dimensional hierarchical flower-like magnesium glycollate sphere was synthesized. Then, the obtained magnesium glycollate sphere was carbonized to obtain magnesia-carbon composite material with enhanced performance. The flower-like carbon material exhibited good adsorption capacity towards polycyclic aromatic hydrocarbons due to the large surface area, the strong π-π interaction force and hydrophobic forces. The flower-like MgO&C material was used as a solid-phase microextraction fiber coating for the analysis of polycyclic aromatic hydrocarbons in real river water samples. Good linearity (5–1000 ng L−1), satisfactory relatively recoveries (86.2–113.5%) and low limits of detections (0.01–0.20 ng L−1) were obtained under the optimized conditions.

Herein, through a facile and energy-friendly approach, thermally stable manganese-derived amorphous stacked nanosheet (MASNS) coatings with controlled wetting property ranging from superhydrophilicity to superhydrophobicity were synthesized. The superhydrophobic MASNS coating exhibited remarkable selectivity and sensitivity in the solid phase microextraction (SPME) of non-polar aromatic analytes, even amid the abundance of polar compounds, due to the superhydrophobic effect and the stacked lamellar structures. The established method was applied to the determination of polycyclic aromatic hydrocarbons (PAHs), featuring low LODs (i.e., 0.14–0.24 ng L−1) and wide linear ranges (e.g., 10–10000 ng L−1). Extraction and desorption conditions were optimized to unleash the potential of the fiber before it was applied to the analysis of target analytes in real water samples, where satisfactory recoveries were obtained (81.7%–114.2%). This work might provide critical insights for the scalable production of superhydrophobic nanosheets as affordable and high-performance adsorbents.

Due to the growing requirement of drug development and the increasing concern of pharmaceutical presence in the environment, bioanalysis of pharmaceuticals has raised much attention to researchers in recent years. However, the complex sample matrices and extremely low content of pharmaceuticals in biological samples are the major constraints. Therefore, great efforts have been made to overcome the subsistent difficulties in recent years, which depend mostly on sample preparation techniques. As a growing trend, developing sample preparation methodologies highlighting high throughput, automatic, on-site, non-invasive and in vivo analysis is highly recommended, which contributes greatly to both biomedical and environmental analysis. Herein, recent advances in sample preparation techniques for quantitative bioanalysis of pharmaceuticals in the past decade are reviewed and summarized, and the relative merits of each sample preparation technique are discussed. Besides, novel techniques such as electromembrane extraction and microfluidic devices are also addressed. Finally, sample preparation techniques which possess the potential for in vivo pharmaceutical analysis will be highlighted as the future trend, and prospects including miniaturization, high specificity and portability will also be discussed.

Solid-phase extraction (SPE) is a popular technique for environmental sample pretreatment. However, SPE usually requires complex sample pretreatment processes, which is time-consuming and inconvenient for real-time and on-site monitoring. Herein, a solvent-free, rapid, and user-friendly SPE device was developed by coating the polydimethylsiloxane (PDMS)/divinylbenzene (DVB) sorbent on the inner wall of a sample bottle. The extraction process and desorption process were both carried out in the bottle. The analytes trapped in the sorbent were thermally desorbed and simultaneously sucked out from the bottle by an air sampling tube equipped on field-portable GC-MS. Different to previous work, the sample pretreatment process didn’t require any complicated and time-consuming steps, such as centrifugation or filtration. The total analysis time for each sample was less than 25 min, which was feasible for rapid on-site detection, and thus avoided the losses and contamination of samples in conventional sample storage and transportation processes. Under optimal conditions, the proposed SPE method exhibited wide linear ranges, low detection limits (0.010–0.036 μg L−1, which were much lower than the maximum levels restricted by the US Environmental Protection Agency and the Chinese GB3838-2002 standard), good intra-bottle repeatability (6.13–7.17%, n = 3) and satisfactory inter-bottle reproducibility (4.73–6.47%, n = 3). Finally, the method was successfully applied to the rapid detection of BTEX in the field. The recoveries of BTEX in spiked water samples ranged from 89.1% to 116.2%. This work presents a novel SPE approach for rapid on-site monitoring in water samples.

Detection of pollutants in animals and plants is crucial for understanding their capability and assessing the risk they pose to the environment and ecology. At present, the research on this area has been benefited from the advances in in vivo solid-phase microextraction (SPME), which reduces the sacrifice of animals and plants, facilitates on-site sampling and sample preparation, enables detection of unstable analytes, and facilitates long-term monitoring. This study summarizes the recent applications of in vivo SPME in detecting pollutants in animals and plants. The samplers, quantification methods, and various cutting-edge applications are discussed in detail. The future trends of using in vivo SPME in environmental analysis are also discussed.

An in vivo uptake and elimination tracing study based on solid phase microextraction (SPME) was conducted to investigate the accumulation, persistence and distribution of organochloride pesticides (OCPs) and organophosphorus pesticides (OPPs) in malabar spinach (Basella alba L.) plants. Uptake and elimination of the pesticides were traced in leaves, stems and roots of living malabar spinach plants. Root concentration factor (RCF), distribution concentration factor (DCF) and transpiration stream concentration factor (TSCF) were calculated based on the in vivo tracing data. The tracing data showed that the OCPs were much more accumulative and persistent than the OPPs in roots, while they were similarly accumulative and persistent in leaves and stems. RCF values of the OPPs or OCPs were likely to increase with the increase in LogKow values except fenthion. Obtained DCF values indicated that OPPs and OCPs were more accumulative in the organs containing more lipids. TSCF values showed that the translocation of OPPs and OCPs from roots to foliage was firstly dependent on the hydrophobicity of the compounds, but also significantly affected by the water solubility. This is the first study of generating RCF, DCF and TSCF data in living plants by in vivo sampling method, which provides a foundation to promote the application of in vivo SPME and improve understanding of contaminant behaviors in living plants.

Solid-phase microextraction (SPME) kinetics in semisolid samples should be different from that in aqueous and gaseous samples, as convection is negligible in semisolid samples but dominates mass transfer in bulk phases of aqueous and gaseous samples. This study developed a mathematical model for describing SPME kinetics in semisolid samples by considering the diffusion of analytes in two compartments, i.e., the fiber coating and the ever-increasing diffusion domain in the sample matrix. The mathematical model predicted that SPME and the desorption of preloaded analytes from the fiber would be isotropic in semisolid samples, while SPME in semisolid samples would not follow the first order kinetics as in aqueous and gaseous samples. The predictions were proven true in the experiment of four pharmaceuticals in agarose gel. In return, it was observed in the experiment that SPME kinetics would deviate more significantly from the first order kinetics for the analytes with higher partition coefficients between t...

A novel solid-phase microextraction (SPME) fiber was prepared by gluing poly(diallyldimethylammonium chloride) (PDDA) assembled graphene oxide (GO)-coated C18 composite particles (C18@GO@PDDA) onto a quartz fiber with polyaniline (PANI). The fiber surface coating was sequentially modified with bioinspired polynorepinephrine, which provided a smooth biointerface and makes the coating suitable for in vivo sampling. The novel custom-made coating was used to extract acidic pharmaceuticals, and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was employed for analysis. The custom-made coating exhibited a much higher extraction efficiency than the previously used commercial polydimethylsiloxane (PDMS) and polyacrylate (PA) coatings. The custom-made coating also possessed satisfactory stability (the relative standard deviations (RSDs) ranged from 1.60% to 10.3% for six sampling-desorption cycles), interfiber reproducibility (the RSDs ranged from 2.61% to 11.5%), and resistance to matrix effects. The custom-made fibers were used to monitor the presence of acid pharmaceuticals in dorsal-epaxial muscle of living fish, and satisfactory sensitivities (limits of detection ranged from 0.13 ng/g to 7.56 ng/g) were achieved. The accuracies were verified by the comparison with liquid extraction. Moreover, the novel fibers were successfully used to monitor the presence of acidic pharmaceuticals in living fish, which demonstrated that the custom-made fibers were feasible for possible long-term in vivo continuous pharmaceutical monitoring.

In vivo solid-phase microextraction (SPME) sampling method coupled with gas chromatography-mass spectrometry (GC-MS) analysis was employed to trace the uptake and elimination of organophosphorus pesticides (OPPs) in two kinds of edible plants, cabbage (Brassica parachinensis) and aloe (Barbadensis). The metabolism of fenthion in aloe was also investigated by the liquid chromatography tandem mass spectrometry analysis (LC-MS/MS) to understand the fate of OPPs in living plants better. Transpiration stream concentration factor (TSCF) and depuration rate constants of the OPPs in living plants were obtained therein. The health risk of the OPPs treated aloe was estimated by the maximum residue limit (MRL) approach, and it revealed that the OPPs were rather safe for their fast degradable property. However, peak concentration of fenthion-sulfoxide was found to exceed the MRL and was higher than that of the parent fenthion, which indicated the potential risk of pesticide metabolites. This study highlighted the application of in vivo SPME for contaminant tracing in different living edible plants. The in vivo tracing method is very convenient and can provide more data to evaluate the risk of different pesticides, which are very important for the safety of agriculture production.

Headspace solid-phase microextraction (HS-SPME) of low volatile analytes from complex aqueous samples can be substantially facilitated by elevating the temperature of the samples. However, many SPME coatings prepared from novel sorptive materials may suffer from low stabilities in hot water steam. Herein, a superhydrophobic metal-organic framework (MOF) derived from decorating the metal-oxo nodes of the amino-functionalized UiO-66(Zr) with phenylsilane was prepared and successfully developed into a novel SPME fiber coating. The highest extraction efficiencies towards the semi-volatile ultraviolet (UV) filters were achieved when the aqueous samples were heated up to 100 °C. It was notable that the lab-made coating exhibited extraordinary stability towards hot water steam, probably because the hydrophobic groups capped on the MOF prevented water molecules from entering and deconstructing its lattice. Even after being treated with water steam under 100 °C for 21 h, the extraction performance of the coating remained unchanged, and the crystal structure of the MOF maintained. Furthermore, a negligible matrix effect was observed even in the samples containing humic acid. Under the optimal extraction and thermal desorption conditions, a method for determining UV filters in aqueous samples was established, which possessed low detection limits (0.6–2.1 ng L−1), wide linear ranges (10–50000 ng L−1), good inter-fiber reproducibility (2.3–6.0%, n = 6), and satisfying intra-fiber repeatability (1.8–5.8%, n = 3). The method was successfully applied in quantifying UV filters in environmental water samples. In addition, the lab-made NH2-UiO-66(Zr)-shp-coated fiber was also suitable for the analysis of polycyclic aromatic hydrocarbons (PAHs). This study provided an effective strategy for preparing MOF coatings that can maintain their crystalline structures and high extraction performances in high-temperature steam.

A novel, low-cost and effective in-needle solid-phase microextraction device was developed for the enrichment of trace polycyclic aromatic hydrocarbons in water samples. The in-needle solid-phase microextraction device could be easily assembled by inserting hydrofluoric acid-etched wires, which were used as adsorbent, into a 22-gauge needle tube within spring supporters. Compared with the commercial solid-phase microextraction fiber, the developed device has higher efficiency for the extraction of polycyclic aromatic hydrocarbons with four to six rings from water samples using the optimized extraction conditions. With gas chromatography equipped with a flame ionization detector, the limits of detection for the polycyclic aromatic hydrocarbons with four to six rings ranged from 0.0020 to 0.0067 ng/mL. The relative standard deviations for one needle and needle-to-needle extractions were in the range of 5.2-9.9% (n = 5) and 3.4-12.3% (n = 5), respectively. The spiked recoveries of the polycyclic aromatic hydrocarbons in tap water samples ranged from 73.2 to 95.4%. This in-needle solid-phase microextraction device could be a good field sampler because of the low sample loss over a long storage time.

Analysis of organic pollutants is usually accomplished in centralized laboratories. However, the time-delayed and time-consuming process is insufficient and risky for precisely detection due to the contamination of vials, the losses of analytes during transportation and storage. Herein, a rapid and highly sensitive on-site detection approach was developed without using any vials by coupling an on-site pre-equilibrium solid phase microextraction (SPME) sampling method with a portable gas chromatography mass spectrometer (portable GC-MS), for the determination of three families of persistent organic pollutants (polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons). Based on sampling-rate (SR) calibration method, the concentrations of target analytes in aquatic systems could be easily determined. Limits of detection (LODs) in the low parts-per-tillion levels (≤5.25 ng·L−1) were obtained for most of the investigated analytes with a total analysis time only ∼30 min. The proposed on-site detection approach was then successfully applied in the determination of persistent organic pollutants in real aquatic environment. A comparable result obtained by liquid extraction (LE) equipped with laboratorial GC-MS demonstrated the accuracy of the on-site detection method. In general, this study demonstrated a rapid and highly sensitive on-site approach, avoiding any risks of contamination during sampling and analysis, for determination of POPs as well as the potential applications for other organic pollutants in aquatic phase.

Miniaturized sample pretreatment platforms have simplified analytical tasks in diverse disciplines. Herein, a novel pipet microextraction (PME) device is reported by making use of the photothermal property of a light-heatable sorbent (LHS) for the first time. Efficient and staining-free heating treatment of small volumes of liquids confined in the PME device is now enabled through light illumination. The light-induced heating treatment is capable of dramatically accelerating solvent elution rates, effectively unlocking bound toxin from its antibody, and rapidly quenching enzymatic activities, thus, provides PME with higher efficiencies and enables its new applications in antibody-intermediated sampling of targeted toxin from stained food surfaces and powders, as well as in accurate revelation of enzymatic reaction kinetics. This study offers a new perspective of designing efficient and versatile microextraction platforms and demonstrates their potential applications in different fields including public security, new drug development, and environmental protection.

In recent years, great concerns have been raised about salicylic acid (SA) and its derivatives as plant regulators. Therefore, precise determination of the distribution of SAs in the living plants is necessary for not only fundamental researches but also the regulating mechanisms. In this study, a custom-made solid phase microextraction (SPME) fiber based on diallyl dimethyl ammonium chloride-assembled graphene oxide-coated C18 composite (C18@GO@PDDA) was proposed for in vivo detection of salicylic acid, acetylsalicylic acid (ASA), 4-methyl salicylic acid（4-SA）and 3-methyl salicylic acid (3-SA) in aloe plants. Under the optimized conditions, the analytical performance evaluated in homogenized aloe plant tissues exhibited low detection limits (1.8–2.8 μg g−1), wide linear ranges (10–5000 μg g−1), and satisfactory reproducibility (relative standard deviations less than 8.4% and 9.3% for inter-fiber and intra-fiber assays, respectively). Under cadmium stress, the developed method was applied for the in vivo tracing of four salicylic acids in aloe plants. A 48-h in vivo tracing revealed that salicylic acids were involved in the pathway of cadmium stress tolerance. To our best knowledge, it is the first effort to realize the in vivo analysis of SA and its derivatives in plants, and it has a made a great step forward in the area of plant hormone analysis.

Solid-phase microextraction (SPME) coupled with liquid chromatograph (LC) is widely used to detect polar and ionic organic compounds, including various pharmaceuticals and endogenous bioactive compounds. In this study, a small-sized insert tube for use in the commercial autosampler vial was designed for eluting the extracted analytes from SPME fibers for LC analysis. By using this custom-made insert tube as an alternative to the commercial insert tube, the volume of the elution solvent was reduced by four-fifths. Even though smaller fractions of the analytes were eluted from the fiber coatings, the analyte concentrations in the elution solutions were substantially increased by using the custom-made insert tube. Therefore, larger amounts of the analytes could be injected to LC and higher signal-to-noise ratios could be achieved, even at smaller injection volumes. Since the elution in the custom-made insert tube was nonexhaustive, four strategies were developed to figure out the extracted amounts in the fiber coatings. In combination with the sampling-rate calibration method, these strategies were successfully used to determine the concentrations of fluoxetine in living tilapias. This study provides a simple but effect way for improving the analytical sensitivity when coupling SPME with LC.

Magnetic molecularly imprinted polymers (MMIPs) have superior advantages in sample pretreatment because of their high selectivity for target analytes and the fast and easy isolation from samples. To meet the demand of both good magnetic property and good extraction performance, MMIPs with various structures, from traditional core-shell structures to novel composite structures with a larger specific surface area and more accessible binding sites, are fabricated by different preparation technologies. Moreover, as the molecularly imprinted polymer (MIP) layers determine the affinity, selectivity, and saturated adsorption amount of MMIPs, the development and innovation of the MIP layer are attracting attention and are reviewed here. Many studies that used MMIPs as sorbents in dispersive solid-phase extraction of complex samples, including environmental, food, and biofluid samples, are summarized. Graphical abstract The application of magnetic molecularly imprinted polymers (MIPs) in the sample preparation procedure improves the analytical performances for complex samples. MITs molecular imprinting technologies.

Fluoroquinolones (FQs) are a group of antimicrobial agents that have been widely used for therapeutic purposes in clinical medicine for human and veterinary diseases, as well as in aquaculture production. Their residues, however, may survive in foods of animal origin, thus causing health risks for human. In this study, a rapid and sensitive method based on in vivo solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed to detect the residues of five FQs in cultured puffer fish (Takifugu obscurus). In vitro fiber evaluation experiment demonstrated that, compared with the thicker polydimethylsiloxane (PDMS) coating (165µm), the custom-made biocompatible C18-PAN fibers (45µm) exhibited much higher extraction efficiencies towards FQs (approximately 9-31 times). The custom-made C18-PAN coating also possessed excellent reproducibility in fish muscle with the intra-fiber relative standard deviations (RSDs) ranging from 11.2% to 14.3% (n = 6) and inter-fiber RSDs ranging from 13.1% to 16.1% (n = 6), which was suitable for in vivo sampling. The custom-made SPME fibers were subsequently applied to determine fluoroquinolones in dorsal-epaxial muscle of living puffer fish. The accuracies were verified through the comparison with traditional liquid extraction (LE) method, and the sensitivities were demonstrated to be satisfying with the limits of detection (LODs) ranging from 0.3ngg-1 to 1.5ngg-1. In general, this study presented a convenient and high-efficient method to determine fluoroquinolones in puffer fish by in vivo sampling.

For the purpose of obtaining a more comprehensive flavor profile, volatile compounds in traditional Chinese dry-cured hams were studied by dual-fiber solid-phase microextraction (SPME) using two fibers simultaneously. By using the selected pair of fibers and under the optimal extraction time, there were total seventy-two volatile compounds identified, which was higher than the mono-fiber SPME method using a single fiber. Out of the seventy-two compounds, twenty-six compounds were not detected by using mono-fiber SPME and five among them are classified as the major aromatic compounds in the literatures. Due to the higher coverage and less tendency for the occurrence of competition among the volatiles, the total amount of volatiles extracted by dual-fiber SPME (510.02 ng/kg) was higher than mono-fiber SPME. Three grades of dry-cured hams were successfully distinguished based on dual-fiber SPME. The volatile compounds belonged to nine chemical families and differed in different grades of dry-cured hams. These results show that dual-fiber SPME is capable of analyzing flavor profiles more comprehensively and distinguishing traditional Chinese dry-cured hams.

Graphene, a novel class of carbon nanostructures, has received great attention as sorbents due to its fascinating structures, ultrahigh specific surface area, and good extraction ability. In this paper, a new type of hierarchical graphene was synthesized through employing a mild and environment-friendly method. Such 3D interconnected graphene own a high specific surface area up to 524 m2 g−1, which is about 2.5 fold larger than the graphene, since the synthetic material has interlayer pores between nanosheets and in-plane pores. Then a superior solid-phase microextraction fiber was fabricated by sequentially coating the stainless steel fiber with silicone sealant film and hierarchical graphene powder. Since the novel hierarchical graphene possessed large surface area and good adsorption property, the as-prepared fiber exhibited good extraction properties of the organochlorine pesticides (OCPs). As for the analytical performance, the as-prepared fiber achieved low detection limits (0.08–0.80 ng L−1) and wide linearity (10–30,000 ng L−1) under the optimal conditions. The repeatability (n=5) for single fiber were between 5.1% and 11%, while the reproducibility (n=3) of fiber-to-fiber were range from 6.2% to14%. Moreover, the fiber was successfully applied to the analysis of OCPs in the Pearl River water.

Although bile acids (BAs) have been suggested as important biomarkers for endocrine diseases, the identification and quantification of different BAs are still challenges due to their enormous species and wide range concentrations. Herein, a copolymer probe based on β‐cyclodextrin (β‐CD) is fabricated through a simple in‐mold photopolymerization for the selective extraction of BAs. Through the unique stereochemical affinity between BAs and the cavity of β‐CD, the custom probe shows superior enriching capacities to series BAs. Moreover, the outstanding extraction ability is proved to be consistent in various interfering conditions, including pH changing and the addition of complex matrix. Further comparison shows that the stereostructure of the nucleus of BAs plays a vital role during the formation of the β‐CD/BA complex, indicating the potential for efficient extraction of other BAs, including their structural analogues or some unknown ones. The developed probe is used for solid phase microextraction, and the limits of detection are lower than 0.075 ng mL−1 by coupling to high performance liquid chromatography‐tandem mass analysis. The results in this study highlight the potential for effective improvement of immediate detection and profiling of BAs in real samples, which will make a tremendous impact in the analytical field or clinical diagnosis.

Elucidating the availability of the bound analytes for the mass transfer through the diffusion boundary layers (DBLs) adjacent to passive samplers is important for understanding the passive sampling kinetics in complex samples, in which the lability factor of the bound analyte in the DBL is an important parameter. In this study, the mathematical expression of lability factor was deduced by assuming a pseudo-steady state during passive sampling, and the equation indicated that the lability factor was equal to the ratio of normalized concentration gradients between the bound and free analytes. Through the introduction of the mathematical expression of lability factor, the modified effective average diffusion coefficient was proven to be more suitable for describing the passive sampling kinetics in the presence of mobile binding matrixes. Thereafter, the lability factors of the bound polycyclic aromatic hydrocarbons (PAHs) with sodium dodecylsulphate (SDS) micelles as the binding matrixes were figured out according to the improved theory. The lability factors were observed to decrease with larger binding ratios and smaller micelle sizes, and were successfully used to predict the mass transfer efficiencies of PAHs through DBLs. This study would promote the understanding of the availability of bound analytes for passive sampling based on the theoretical improvements and experimental assessments.