Preparation of silica-supported carbon by Kraft lignin pyrolysis, and its use in solid-phase extraction of fluoroquinolones from environmental waters

Innovative chitin-glucan based material obtained from mycelium of wood decay fungal strains

Fungi are an alternative source to animal-based chitin. In fungi, chitin fibrils are strongly interconnected and bound with glucans that justify the unique matrix. The present study aimed to extract chitin and glucans from the mycelium of several wood decay fungal strains in order to obtain flexible materials and to check correlations between chitin content and the mechanical properties of these materials. Five strains were chosen in consideration of their different cell wall chemical composition (high content of α-glucans, β-glucans or chitin) to evaluate how these differences could influence the mechanical and chemical characteristics of the material. The fungal strains were cultivated in liquid-submerged dynamic fermentation (both flasks and bioreactor). Chitin and glucans were crosslinked with acetic acid and plasticized with glycerol to obtain flexible sheets. Abortiporus biennis, Fomitopsis iberica and Stereum hirsutum strains were found to adapt to produce material with adequate flexibility. The obtained materials were characterized by Thermogravimetric analysis (TGA) for the understanding of the material composition. The material obtained from each species was mechanically tested in terms of tear strength, elongation at break, and Young's modulus.

The Ultratrace Determination of Fluoroquinolones in River Water Samples by an Online Solid-Phase Extraction Method Using a Molecularly Imprinted Polymer as a Selective Sorbent

Fluoroquinolones (FQs) are broad-spectrum antibiotics widely used to treat animal and human infections. The use of FQs in these activities has increased the presence of antibiotics in wastewater and food, triggering antimicrobial resistance, which has severe consequences for human health. The detection of antibiotics residues in water and food samples has attracted much attention. Herein, we report the development of a highly sensitive online solid-phase extraction methodology based on a selective molecularly imprinted polymer (MIP) and fluorescent detection (HPLC-FLD) for the determination of FQs in water at low ng L−1 level concentration. Under the optimal conditions, good linearity was obtained ranging from 0.7 to 666 ng L−1 for 7 FQs, achieving limits of detection (LOD) in the low ng L−1 level and excellent precision. Recoveries ranged between 54 and 118% (RSD < 17%) for all the FQs tested. The method was applied to determining FQs in river water. These results demonstrated that the developed method is highly sensitive and selective.

Use of hydroxypropyl β-cyclodextrin hybrid monolithic material as adsorbent for dispersive solid-phase extraction of fluoroquinolones from environmental water samples

In this study, the hydroxypropyl β-cyclodextrin hybrid monolithic material was fabricated and firstly applied as adsorbent for dispersive solid-phase extraction coupled with high-performance liquid chromatography to detect trace-level seven fluoroquinolones in water samples. The prepared hydroxypropyl β-cyclodextrin hybrid monolithic material was characterized by fourier transform infrared spectroscopy, scanning electron microscopy and adsorption experiments, which showed excellent specific adsorption to the target fluoroquinolones. Under the optimized conditions, the extraction methodology showed satisfactory precision with relative standard deviations between 2.6 and 5.6%, good linearity (R² ≥0.9990) and satisfactory recoveries (82.5∼91.8%). The limits of detection and limits of quantification of the method were in the range of 0.4∼1.2 ng mL^-1 and 1.4∼4.0 ng mL^-1 respectively, which confirmed the possibility of quantifying trace levels. Furthermore, the material could be reused at least five times. These results demonstrated that the hydroxypropyl β-cyclodextrin hybrid monolithic material was a promising adsorbent for fluoroquinolones, and the established method combined dispersive solid-phase extraction with high-performance liquid chromatography was suitable for the determination of fluoroquinolones in aqueous samples. This article is protected by copyright. All rights reserved.

Macro-microporous zeolitic imidazole framework-8/cellulose aerogel for semi-automated pipette tip solid phase extraction of fluoroquinolones in water

In this study, Zeolitic Imidazole Framework-8/cellulose aerogel (ZIF-8/CA) hybrid was successfully fabricated through a simple doping method and ZIF-8 acted as the major component for adsorption. In order to elucidate the adsorption mechanism deeply, molecular simulation was adopted to the expound the interaction modes between ZIF-8 and the fluoroquinolones (FQs). ZIF-8/CA was used as the adsorbent for semi-automated pipette tip solid phase extraction (PT-SPE). In combination with high performance liquid chromatography tandem fluorescence detector (HPLC-FLD), the established method was successfully employed to determine trace amount of FQs in water samples. Extraction parameters such as the content of ZIF-8, pH of sample solution, volume of sample, flow rate of sampling, type and volume of elution solvent were investigated. Under the optimized conditions, satisfactory linearity was achieved with the correlation coefficient (R²) ranging from 0.9954 to 0.9992. The limits of detection were in the range of 0.337-1.707 ng L^-1. And the recoveries varied from 75.9% to 96.8% with RSD less than 8.0%. The established method was demonstrated to be sensitive, efficient and convenient.

Preparation of amine-modified lignin and its applicability toward online micro-solid phase extraction of valsartan and losartan in urine samples

In the present work, with the focus on an environmentally-friendly approach, some gels were prepared by synthesizing amine-modified lignin, extracted from sugarcane bagasse, and further esterification and subsequent freeze-drying. These lignin-based gels were implemented as extractive phases in an online micro-solid phase extraction (μSPE) setup in conjunction with high performance liquid chromatography (HPLC) with UV detector. The developed method was used for analytical determination of valsartan and losartan in urine samples. To study the effect of the functionalization process, the efficiency of the unmodified lignin and the functionalized lignin were compared both in the absence and the presence of graphene oxide (GO), presumably as a suitable doping agent. Surprisingly, higher extraction efficiency for the functionalized lignin, compared to both unmodified lignin and GO was observed. The amination process for the prepared gel was analyzed and proved by CHNS elemental analysis and Fourier transform infrared (FT-IR) spectroscopy. The morphology of sorbet was investigated via scanning electron microscope (SEM) imaging and a nanoscale cauliflower feature was observed. The method was optimized and subsequently applied to the analysis of the urine samples. Limits of detection (LOD) of 8 and 6 µg L ^- 1, limits of quantification (LOQ) of 27 and 20 µg L ^- 1 and linear dynamic range (LDR) of 27-2000 and 20-2000 µg L ^- 1 with intraday relative standard deviations (RSD%) of 4 and 3% were obtained for valsartan and losartan, respectively. The whole online μSPE-HPLC setup was conveniently used for the analysis of a patient urine sample and a quantity of 352 μg L ^- 1 of losartan was found. Acceptable relative recoveries (109-108 and 95-94% for valsartan and losartan) revealed the analytical potential of the method for the determination of drugs in complex urine samples.

Magnetic Photocatalyst for Wastewater Tertiary Treatment at Pilot Plant Scale: Disinfection and Enrofloxacin Abatement

In this work, we have tested a photocatalytic material consisting of a core of SiO2/Fe3O4 coated with TiO2 (Magnox) for plausible tertiary wastewater treatment. For this, a pilot plant of 45 L equipped with an Ultraviolet light (UVC) lamp was employed to study the degradation of a model contaminant, enrofloxacin (ENR), as well as water disinfection (elimination of Escherichia coli and Clostridium perfringens). The influence of different operational conditions was explored by means of dye (rhodamine-B) decolorization rates, analyzing the effects of photocatalyst quantity, pH and recirculation flow rates. The magnox/UVC process was also compared with other four Advanced Oxidation Processes (AOPs): (i) UVC irradiation alone, (ii) hydrogen peroxide with UVC (H2O2/UVC), (iii) Fenton, and (iv) photo-Fenton. Although UVC irradiation was efficient enough to produce total water disinfection, only when employing the AOPs, significant degradations of ENR were observed, with photo-Fenton being the most efficient process (total enrofloxacin removal in 5 min and c.a. 80% mineralization in 120 min, at pH0 2.8). However, Magnox/UVC has shown great pollutant abatement effectiveness under neutral conditions, with the additional advantage of no acid or H2O2 addition, as well as its plausible reuse and simple separation due to its magnetic properties.

Preparation of magnetic hydrogel microspheres of lignin derivate for application in water

A low-cost and well-separated approach is introduced for adsorption pollutants in water. Chemical modified lignin is prepared with diethylenetriamine to enhance the reaction activities, then used to prepare lignin derivate magnetic hydrogel microspheres (LDMHMs) via blending with Fe₃O₄. The LDMHMs are successful prepared by the determination of FT-IR data, and the morphology shown from SEM imagine indicates the LDMHMs are in nanosized. The prepared LDMHMs are used as adsorbents for organic dyes, such as methylene blue (MB), methyl orange (MO) and malachite green (MG), the plateaus data are 43 mg/g, 39 mg/g and 155 mg/g, respectively. For inorganic pollutions, such as Pb²⁺, Hg²⁺ and Ni²⁺, the plateaus data are 33 mg/g, 55 mg/g and 23 mg/g, respectively. The adsorption data of unmodified lignin are 2.6 mg/g (Pb²⁺), 3.3 mg/g (Hg²⁺), 2.1 mg/g (Ni²⁺), 8 mg/g (MB), 10 mg/g (MG) and 2 mg/g (MO) in the same condition. The adsorbents are recycled by magnetic separation, regenerating from acid condition and reused for multiple cycles. The regeneration ratios are all above 90%, indicating a highly reusability and further reducing the cost of the treatment.

Polypyrrole nanotubes for electrochemically controlled extraction of atrazine, caffeine and progesterone

Polypyrrole (PPy) was electrochemically synthesized with charge control on the surface of a steel mesh. Two different morphologies (globular and nanotubular) were created and characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The modified electrodes were used as extraction phases in solid-phase extraction (SPE) and electrochemically controlled solid-phase extraction (EC-SPE) of atrazine, caffeine and progesterone. Raman spectroscopy was employed for the structural characterization of PPy after long exposure to the analytes. The electrochemical behavior was studied by cyclic voltammetry which revealed the higher capacitive behavior of polypyrrole nanotubes because of the huge superficial area, also no electrocatalytical behavior was observed evidencing the strong adsorption of the analytes on the PPy surface. The effects of the PPy oxidation state on the extraction performance were evaluated by in-situ electrochemical sorption experiments. The sorption capacity was evaluated by gas chromatography coupled to mass spectrometry (GC-MS). The method displays good stability, repeatability and reproducibility. The limits of detection range between 1.7-16.7 μg L^-1. Following the extraction of river water samples, it was possible to identify the presence of other endogenous organic compounds besides the analytes of interest. This indicates the potential of the method and material developed in this work. Graphical abstract Schematic representation of a steel mesh electrode covered with polypyrrole nanotubes used as extraction phase for separation of contaminants from aqueous samples. The oxidation level of polypyrrole was electrochemically tuned by which the adsorption of analytes is deeply affected.

Metal-organic framework-monolith composite-based in-tube solid phase microextraction on-line coupled to high-performance liquid chromatography-fluorescence detection for the highly sensitive monitoring of fluoroquinolones in water and food samples

In this study, a new metal-organic framework-monolith composite for in-tube solid phase microextraction phase (IT-SPME) of fluoroquinolones (FQs) was prepared. 4-Vinylbenzoic acid was copolymerized with ethylenedimethacrylate in a fused silica capillary to form porous monolith. After that, zeolitic imidazolate frameworks (ZIF-8) were synthesized in situ within the pores and the surface of the monolith by controlled layer-by-layer self-assembly of Zn²⁺ and imidazole. The introduction of ZIF-8 enhanced the surface area of monolith composite, and thus, improving the extraction performance of IT-SPME for FQs obviously. Under the optimized conditions, a highly sensitive method for the monitoring of FQs residue in water and honey samples was developed by the on-line combination of IT-SPME with high-performance liquid chromatography with fluorescence detection (HPLC-FLD). The limits of detection (S/N = 3) for the targeted FQs in water and honey samples were as low as 0.14-0.61 ng/L and 0.39-1.1 ng/L, respectively. The relative standard deviations (RSDs) for intra-day and inter-day assay variability were less than 10% in all samples. The established on-line IT-SPME-HPLC-FLD was successfully used to detect ultra-trace FQs in environmental water and honey samples. Recoveries at different spiked concentrations ranged from 80.1% to 119% and 80.2-117% for water and honey samples, respectively, with satisfactory reproducibility. Compared to up-to-date reported methods, the proposed approach exhibits some features such as high sensitivity, convenience, partial automation, low consumptions of sample and solvent.

Simultaneous determination of sulfonamides and fluoroquinolones from environmental water based on magnetic double-template molecularly imprinting technique

In this work, a fast and selective method based on magnetic extraction is presented for the simultaneous extraction of sulfonamides (SAs) and fluoroquinolones (FQs), followed by liquid chromatography-tandem mass spectrometry detection. In this method, magnetic surface double-template molecularly imprinted polymers (MSdt-MIPs) with superparamagnetic property and high selectivity toward both SAs and FQs were synthesized and directly applied to the simultaneous extraction of SAs and FQs from environmental water as magnetic adsorbents. The extraction and enrichment procedures could be accomplished in one single step by stirring the mixture of MSdt-MIPs and water sample, and the MSdt-MIPs with adsorbed analytes were easily separated from the water sample by a magnet afterwards. The adsorption mechanism of MSdt-MIPs was investigated by employing the adsorption thermodynamic and kinetic studies, and the selectivity of the MSdt-MIPs toward target analytes was evaluated through the selectivity test. For validation of the proposed method, the matrix effect was evaluated and compared to that of the traditional SPE method. Excellent linearity (R > 0.9990) for both SAs and FQs were obtained in the concentration range of 20-2000 ng L^-1, and the limits of detection are in the range of 3.0-4.7 ng L^-1 for SAs while 4.1-6.1 ng L^-1 for FQs. Finally, the proposed method was successfully applied to the simultaneous determination of SAs and FQs in several environmental water samples.

Thermally condensed humic acids onto silica as SPE for effective enrichment of glucocorticoids from environmental waters followed by HPLC-HESI-MS/MS

Pristine humic acids (HAs) were thermally condensed onto silica microparticles by a one-pot, inexpensive and green preparation route obtaining a mixed-mode sorbent (HA-C@silica) with good sorption affinity for glucocorticoids (GCs). The carbon-based material, characterized by various techniques, was indeed applied as the sorbent for fixed-bed solid-phase extraction of eight GCs from river water and wastewater treatment plant effluent, spiked at different concentration levels in the range 1-400 ng L^-1. After sample extraction, the target analytes were simultaneously and quantitatively eluted in a single fraction of methanol, achieving enrichment factor 4000 and 1000 in river water and wastewater effluent, respectively. Full recovery for all compounds, was gained in the real matrices studied (80-125% in river water, 79-126% in wastewater effluent), with inter-day precision showing relative standard deviations (RSD) below 15% and 18% (n = 3), for river and wastewater effluent, correspondingly. The high enrichment factors coupled with high-performance liquid chromatography tandem mass spectrometry quantification (MRM mode) provided method quantification limits of 0.009-0.48 ng L^-1 in river water and 0.06-3 ng L^-1 in wastewater effluent and, at the same time, secure identification of the selected drugs. As also evidenced by comparison with literature, HA-C@silica proved to be a valid alternative to the current commercial sorbents, in terms of extraction capability, enrichment factor, ease of preparation and cost. The batch-to-batch reproducibility was assessed by recovery tests on three independently prepared HA-C@silica powders (RSD lower than 7%).

Development and Validation of a Reproducible and Label-Free Surface Plasmon Resonance Immunosensor for Enrofloxacin Detection in Animal-Derived Foods

This study describes the development of a reproducible and label-free surface plasmon resonance (SPR) immunosensor and its application in the detection of harmful enrofloxacin (ENRO) in animal-derived foods. The experimental parameters for the immunosensor construction and regeneration, including the pH value (4.5), concentration for coating ENRO-ovalbumin conjugate (ENRO-OVA) (100 μg·mL⁻¹), concentration of anti-ENRO antibody (80 nM) and regeneration solution (0.1 mol·L⁻¹ HCl) were evaluated in detail. With the optimized parameters, the proposed SPR immunosensor obtained a good linear response to ENRO with high sensitivity (IC₅₀: 3.8 ng·mL⁻¹) and low detection limit (IC₁₅: 1.2 ng·mL⁻¹). The proposed SPR immunosensor was further validated to have favorable performances for ENRO residue detection in typical animal-derived foods after a simple matrix pretreatment procedure, as well as acceptable accuracy (recovery: 84.3–96.6%), precision (relative standard deviation (n = 3): 1.8–4.6%), and sensitivity (IC₁₅ ≤ 8.4 ng·mL⁻¹). Each SPR chip for analysis can be reused at least 100 times with good stability and the analysis cycle containing the steps of sample uploading/chip regeneration/baseline recovery can be completed within 6 min (one cycle) and auto-operated by a predetermined program. These results demonstrated that the proposed SPR immunosensor provided an effective strategy for accurate, sensitive, and rapid detection for ENRO residue, which has great potential for routine analysis of large numbers of samples for measuring different types of compounds.