Extraction of tetracycline in food samples using biochar microspheres prepared by a Pickering emulsion method

A chiral porous organic cage-modified restricted-access material achieves online analysis of serum samples containing enantiomers and positional isomers

Restricted-access materials (RAMs) allow biological samples to directly enter the chromatographic column for analysis owing to the steric exclusion function ability for biomolecules and extraction function for small-molecule analytes, which promoting the development of rapid, efficient, and automated in vivo drug analysis. Few reports on chiral RAMs that have been used to analyze enantiomers and positional isomers in serum by direct injection in currently. In this study, a chiral porous organic cage material RCC3 was innovatively introduced into the inner surface of silica gel and modified the outer surface with polyethylene glycol to prepare a novel type of chiral RAM-RCC3, and reported the use of chiral RAM-RCC3 as a stationary phase for the separation of chiral compounds and positional isomers in blank serum using high-performance liquid chromatography. The novel RAM-RCC3 column exhibited good performance in the online analysis of nine enantiomers and five positional isomers in serum samples. The effects of analyte mass, temperature, and composition of the mobile phase on the separation of o-, m-, and p-nitrophenol in serum samples using the RAM-RCC3 column were also investigated. Even after 300 injections, the RAM-RCC3 column exhibited good reproducibility and stability. These results indicate the potential of the chiral RAM-RCC3 column as a stationary phase for direct injection analysis of both chiral separation and positional isomers in biological samples, which also rendering it suitable to be further developed as a new type of RAM for online analysis of various small molecules in biological samples.

Ecofriendly and biocompatible biochars derived from waste-branches for direct and efficient solid-phase extraction of benzodiazepines in crude urine sample prior to LC-MS/MS

Biochars (BCs) derived from waste-branches of apple tree, grape tree, and oak were developed for direct solid-phase extraction (SPE) of five benzodiazepines (BZDs) in crude urine samples prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination. Scanning electron microscopy, elemental analyzer, X-ray diffractometry, N2 adsorption/desorption experiments, and Fourier transform infrared spectrometry characterizations revealed the existence of their mesoporous structure and numerous oxygen-containing functional groups. The obtained BCs not only possessed high affinity towards BZDs via π-π and hydrogen bond interactions, but also afforded the great biocompatibility of excluding interfering components from undiluted urine samples when using SPE adsorbents. Variables affecting SPE of target analytes were systematically optimized including pH, ionic strength, dilution ratio, washing solution, desorption solvent, and its volume. The method of BC-based SPE combined with LC-MS/MS exhibited a wide linear range of 0.03-100 ng/mL, a low detection limit of 0.01-0.08 ng/mL, and satisfactory recovery of 77.6-106% for the studied BZDs. Notably, this method allowed the possibility of direct loading of undiluted urine samples and avoided tedious filtration and dilution steps, which significantly simplified the pretreatment process. Additionally, these BC sorbents derived from waste-branches were ecofriendly and cost-effective, providing a sustainable alternative for the traditional SPE sorbents. Thus, the proposed method has promising application for ecofriendly, simple, efficient, and reliable monitoring of BZDs in urine samples.

Research on the Selective Extraction of Oxibendazole Residues in Animal-Derived Food Using Molecularly Imprinted Polymers

To achieve specific adsorption-based sample preparation for the poorly soluble veterinary drug oxibendazole, this study employed 4-vinylpyridine as the functional monomer and conducted radical polymerization on the surface of functionalized silica nanoparticles to synthesize a surface molecularly imprinted polymer (OBZMIP). This OBZMIP exhibited good adsorption capacity for oxibendazole within 30 min, with its adsorption behavior conforming to the pseudo-second-order kinetic and Langmuir models, predicting a maximum adsorption capacity of 4.93 mg/g. After five adsorption-desorption cycles, the adsorption capacity remained unchanged, demonstrating excellent reusability. In a mixed system containing eight similar compounds, the selectivity coefficients ranged from 1.3 to 16.9, indicating outstanding specific recognition ability. Utilized as an adsorbent packing material for solid-phase extraction, the prepared OBZMIP demonstrated significantly high recovery rates in the extraction of oxibendazole from four distinct meat samples. Therefore, OBZMIP holds promising applications in the selective extraction of veterinary drug oxibendazole residues during the pretreatment of meat samples.

Green hairy basil seed mucilage biosorbent for dispersive solid phase extraction enrichment of tetracyclines in bovine milk samples followed by HPLC analysis

Unmodified hairy basil seed mucilage (Ocimum basilicum L.), with attractive features as structural functionality and adsorption capacity, was employed as a green biosorbent for dispersive solid phase extraction and enrichment of oxytetracycline, tetracycline, and doxycycline before quantitation by HPLC-UV for the first time. Hairy basil crushed seed increased the contacting surface area and was completely dispersed in the sample solution to extract tetracyclines under acidic condition with the assistance of ultrasonic waves. The analytes in the extraction phase were separated on a C18 column under isocratic condition with a mobile phase consisted of acetonitrile and trifluoroacetic acid. Influence of chemical and physical variables on the extraction efficiency of the developed method was investigated and optimized systematically. Under the optimal condition of all experimental parameters, good linear ranges were obtained at 15.0-500 μg L-1 for tetracyclines with determination coefficients more than 0.9994. Limits of detection (LODs) and limits of quantitation (LOQs) ranged 5.0-7.0 and 15.0 μg L-1, respectively. Relative standard deviations (RSDs) of the proposed method at 100 and 300 μg L-1 for TCs were less than 13 % and 10 %, respectively with percentage TC recoveries from spiked standard ranging 83.1-109.9 %. This simple, reliable, cost-effective, and environmentally friendly method was successfully applied for the analysis of tetracycline residues in milk. The greenness of the proposed method was assessed using the Analytical Eco-Scale and AGREE protocol.

Inhibition performance of almond shell hydrochar-based fish oil emulsion gel on Klebsiella pneumonia inoculated fish skin and its characteristics

In this study, the inhibition potential against Klebsiella pneumoniae (K. pneumoniae) and the characterization of fish oil (FO) emulsion gel (EGE) containing almond shell hydrochar (AH) were investigated. Oily water of mullet liver was emulsified using tween 80, then gelled using gelatin and finally immobilized into hydrochar using an ultrasonic homogenizer. Characteristics and surface analysis of hydrochar-based emulsion gel (HEGE) were examined using FTIR and SEM. Stability, particle size distribution and zeta potential of HEGE were measured. In this study, a zeta potential of -18.46 indicated that HEGE was more stable than EGE (35.7 mV). The addition of hydrochar to the emulsion gel containing micro-droplets enabled the structure to become fully layered and stable. Time-dependent inactivation of K. pneumoniae exposed to HEGE and fixed in 6 mm-fish skin was evaluated for the first time in this study. While the highest log reduction and percent reduction in the bacterial count were achieved within 5 min with 0.87 CFU/cm2 and 86.60% with EGE, the lowest log reduction and percent reduction were achieved with 0.003 CFU/cm2 and 0.082% with HEGE in 30 min. In conclusion, the almond shell hydrochar-immobilized emulsion gel is a functional adsorbent that can inhibit K. pneumonia, and its stability and performance make it a unique candidate for further studies in this field.

Molecularly Imprinted Polymers Using Yeast as a Supporting Substrate

Molecularly imprinted polymers (MIPs) have gained significant attention as artificial receptors due to their low cost, mild operating conditions, and excellent selectivity. To optimize the synthesis process and enhance the recognition performance, various support materials for molecular imprinting have been explored as a crucial research direction. Yeast, a biological material, offers advantages such as being green and environmentally friendly, low cost, and easy availability, making it a promising supporting substrate in the molecular imprinting process. We focus on the preparation of different types of MIPs involving yeast and elaborate on the specific roles it plays in each case. Additionally, we discuss the advantages and limitations of yeast in the preparation of MIPs and conclude with the challenges and future development trends of yeast in molecular imprinting research.

Biochar nanosphere-functionalized carbon fibers for in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons in environmental water followed by liquid chromatography and diode array detection

In order to improve the extraction ability of carbon fibers (CFs) for microextraction of polycyclic aromatic hydrocarbons (PAHs), biochar nanospheres derived from glucose were in-situ grown onto the surface of CFs via hydrothermal synthesis. The surface morphology and elemental composition of biochar nanospheres-CFs were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. Thereafter, the biochar nanosphere-CFs were pulled into the polyetheretherketone tube for solid-phase microextraction, and the tube was combined with high-performance liquid chromatography-diode array detector to online detect PAHs. With the help of π-stacking, hydrophobic, and hydrophilic effect of biochar nanospheres, the extraction efficiency of CFs was greatly enhanced (enrichment factor increased by 293% compared with  the original). The conditions affecting the analytical performance (sampling volume, sampling rate, methanol content, and desorption time) were investigated. Under the optimal conditions, an online analytical method for microextraction and determination of several PAHs was developed, and satisfactory results were achieved. The limits of detection were 0.003-0.010 ng mL-1 owing to high enrichment effect (2973-3600), linearity ranged from  0.010-15.0 ng mL-1, and relative standard deviations were 0.4%-1.6% (intra-day) and 2.4%-4.4% (inter-day), respectively. The method was applied to analyze environmental water samples (rain water, snow water, and river water), and spiked recoveries within 80.0%-119% were obtained.

Preparation of biochar-based surface molecularly imprinted polymers and evaluation of their selective adsorption and removal of carbaryl from rice and corn

The residue of carbaryl in food is a threat to human health. In this study, activated soybean shell biochar (A-SBC) was used as a carrier, methacrylic acid (MAA) was used as a functional monomer, and carbaryl was used as a template molecule to synthesize the activated biochar surface molecularly imprinted polymer (A-SBC@MIP). The synthesized A-SBC@MIP was characterized by SEM, FT-IR, XRD and XPS techniques, and then applied as adsorbent for carbaryl removal. The adsorption capacity of A-SBC@MIP for carbaryl was 8.6 mg‧g-1 and the imprinting factor was 1.49 at the optimum ionic strength and pH. The kinetic and isothermal data indicated that it had fast mass transfer rate and high binding capacity(Qmax=47.9 mg‧g-1). A-SBC@MIP showed good regenerative properties and the adsorption of carbaryl was excellent in its structural analogues. A solid-phase extraction (SPE) column composed of A-SBC@MIP was developed for the detection of rice and corn under optimized conditions, with recoveries of 93-101% for the spiked carbaryl. The limit of detection (LOD) of the method was 3.6 μg‧kg-1 with good linearity (R2=0.994) in the range of 0.01-5.00 mg‧L-1. The results show that the developed MIPs-SPE can enrich carbaryl from food samples as a specific and cost-effective method.

Triblock copolymer–grafted restricted access materials with zwitterionic polymer outer layers for highly efficient extraction of fluoroquinolones and exclusion of proteins

High-selectivity and high-exclusion restricted access materials (RAMs) benefit the analysis of biological samples. Herein, triblock copolymer-functionalized poly(4-vinylbenzyl chloride-co-divinylbenzene) (P_VBC/DVB) microspheres were prepared via the sequential surface-initiated atom radical polymerization of hydrophobic styrene (St), ionic vinylimidazole (VIm), and zwitterionic sulfobetaine methacrylate (SBMA), affording RAMs with multiple interaction-adsorption sites and zwitterionic polymer exclusion sites on the internal and external surfaces of P_VBC/DVB. The preferential extraction of fluoroquinolones (FQs) is realized based on the hydrophobic/π-π/ion exchange interactions due to the grafted poly-St-VIm, and the zwitterionic poly-SBMA block in the triblock copolymers can efficiently exclude various proteins. A sensitive detection method for FQs in chicken was established by solid phase extraction with RAMs as adsorbent combined with UPLC-MS/MS, achieving wide linearity (2.0-200.0 ng mL^-1), low limit of detection (0.5 μg kg^-1) and limit of quantification (1.5 μg kg^-1), and good inter- and intraday precision with satisfactory recoveries (104.1%-117.7% and 115.3%-121.2% with RSDs < 12%).

A sensitized ratiometric fluorescence probe based on N/S doped carbon dots and mercaptoacetic acid capped CdTe quantum dots for the highly selective detection of multiple tetracycline antibiotics in food

A ratiometric fluorescent probe based on N/S doped carbon dots (N/S-CQDs) and mercaptoacetic acid capped CdTe quantum dots (TGA-CdTe QDs) with sensitized and self-calibration functions was constructed to sensitively detect multiple tetracycline antibiotics (TCs). N/S-CQDs could attach stably to TGA-CdTe QDs and form a new composite ratiometric fluorescent probe that had a more than tenfold increase in sensitivity to TCs compared with each single QD. The probe could detect four common TCs as the color of the probe changed from bright red to dark red, and the limit of detection (LOD) was 1.47 × 10^-2-1.78 × 10^-2 mg/L. Practical applications of the probe in food and urine were also verified with recovery rates of 95.21%-104.97%. Due to the abundant spectral fingerprints provided by both QDs, this novel probe could accurately recognize not only different single TCs but also mixed TC samples even in actual samples combined with chemometrics.

A review of antibiotics and antibiotic resistance genes (ARGs) adsorption by biochar and modified biochar in water

Antibiotics have been used in massive quantities for human and animal medical treatment, and antibiotic resistance genes (ARGs) are of great concern worldwide. Antibiotics and ARGs are exposed to the natural environment through the discharge of medical wastewater, causing great harm to the environment and human health. Biochar has been widely used as a green and efficient adsorbent to remove pollutants. However, pristine and unmodified biochars are not considered sufficient and efficient to cope with the current serious water pollution. Therefore, researchers have chosen to improve the adsorption capacity of biochar through different modification methods. To have a better understanding of the application of modified biochar, this review summarizes the biochar modification methods and their performance, particularly, molecular imprinting and biochar aging are outlined as new modification methods, influencing factors of biochar and modified biochar in adsorption of antibiotics and ARGs and adsorption mechanisms, wherein adsorption mechanism of ARGs on biochar is found to be different than that of antibiotics. After that, the directions of biochar and modified biochar worthy of research and the issues that need attention are proposed. It can be noted that under the current dual carbon policy, biochar may have wider application prospects in future.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

Preparation and evaluation of a chitosan modified biochar as an efficient adsorbent for pipette tip-solid phase extraction of triazine herbicides from rice

The low allowable limit of triazine herbicides (THs) in rice makes it imperative to develop novel sample pretreatment methods for extraction and preconcentration of THs. Herein, a phosphoric acid activated biochar (PBC) was prepared and modified by chitosan (CS). For THs with different polarities, CS-PBC with multiple interaction sites exhibited satisfactory chemisorption. On this basis, a CS-PBC-based pipette tip-solid phase extraction (PT-SPE) was developed combined with HPLC to extract THs from rice. Low limits of detection (1.41-3.35 ng g^-1), satisfactory linearity (0.01-2.00 μg g^-1, R² > 0.9974) and recoveries (96.13-116.25 %) were obtained with acceptable inter-day and intra-day precision (RSD ≤ 13.60 %). CS-PBC showed superior performance to three commercial single-mode adsorbents and comparable results to a hydrophilic-lipophilic balance adsorbent. The study explored the feasibility of PT-SPE for extracting THs from rice and broadened the application of plant biochar as an environmentally-friendly matrix in food sample pretreatment.

Green synthesis of walnut shell hydrochar, its antimicrobial activity and mechanism on some pathogens as a natural sanitizer

Hydrochar of waste walnut shells (WSH) was synthesized in the eco-friendly subcritical water medium (SWM) and its potential to fight against Klebsiella pneumoniae (K. pneumoniae), Staphylococcus aureus (S. aureus), Candida albicans (C. albicans) and Candida parapsilosis (C. parapsilosis) was investigated. Minimum Inhibitory Concentration (MIC) values of the WSH were 3.01 g/mL, 2.06 g/mL, 1.95 g/mL, and 3.12 g/mL for K. pneumoniae, S. aureus, C. albicans and C. parapsilosis, respectively. Survival of the pathogens was investigated by 3 min surface disinfection test exposure to WSH. While the highest inhibition was seen for C. parapsilosis (96.67%) on paper surface with 0.3 g/mL of bovine serum albumin (BSA), the lowest inhibition was determined for C. albicans (6.44%) on the plastic glass surface with 3 g/mL of BSA. An increase in protein, DNA, and potassium ion (K⁺) leakage was observed after microorganisms were incubated with WSH. This study provided an experimental basis for the practical application of WSH as a natural sanitizer agent.

Recent advances and applications of molecularly imprinted polymers in solid-phase extraction for real sample analysis

Sample pretreatment is essential for the analysis of complicated real samples due to their complex matrices and low analyte concentrations. Among all sample pretreatment methods, solid-phase extraction is arguably the most frequently used one. However, the majority of available solid-phase extraction adsorbents suffer from limited selectivity. Molecularly imprinted polymers are a type of tailor-made artificial antibodies and receptors with specific recognition sites for target molecules. Using molecularly imprinted polymers instead of conventional adsorbents can greatly improve the selectivity of solid-phase extraction, and therefore molecularly imprinted polymer-based solid-phase extraction has been widely applied to separation, clean up and/or preconcentration of target analytes in various kinds of real samples. In this article, after a brief introduction, the recent developments and applications of molecularly imprinted polymer-based solid-phase extraction for determination of different analytes in complicated real samples during the 2015-2020 are reviewed systematically, including the solid-phase extraction modes, molecularly imprinted adsorbent types and their preparations, and the practical applications of solid-phase extraction to various real samples (environmental, food, biological, and pharmaceutical samples). Finally, the challenges and opportunities of using molecularly imprinted polymer-based solid-phase extraction for real sample analysis are discussed.

Novel molecularly imprinted malachite green bifunctional imprinted microspheres through Pickering emulsion polymerization

The molecular imprinting process and solid particles confer MIP-MGs with excellent selective recognition and strong synergy of adsorption-photocatalysis towards MG removal.

Facile Synthesis of Mixed-Mode Weak Anion-Exchange Microspheres via One-Step Pickering Emulsion Polymerization for Efficient Simultaneous Extraction of Strongly and Weakly Acidic Drugs from Reservoir Water

Poly(2-(diethylamino)ethyl methacrylate-co-divinylbenzene) (poly(DEAEMA-co-DVB)) microspheres with mixed-mode weak anion-exchange (WAX) character were successfully fabricated for the first time via facile one-step Pickering emulsion polymerization. The obtained poly(DEAEMA-co-DVB) particles had good spherical geometry, uniform particle size in the range of 30-40 µm, a large specific surface area of 575 m²/g, and a pore size range of 5-30 nm, according to the SEM and nitrogen adsorption-desorption results. Using these mixed-mode WAX microspheres as packing material, a reliable and robust analytical method based on solid phase extraction and high performance liquid chromatography with ultraviolet detection (SPE-HPLC-UV) was developed for simultaneous determination of six strongly and weakly acidic nonsteroidal anti-inflammatory drugs (NSAIDs, niflumic acid, diflunisal, naproxen, ketoprofen, mefenamic acid, and diclofenac) in reservoir water. Under optimized conditions, it was applicable to preconcentrate up to 500 mL of reservoir water samples on the WAX cartridges with satisfying recoveries (88-96%) for all the NSAIDs tested. The limits of detection were in the range of 0.002-0.025 μg L^-1, respectively. Our results showed that the developed mixed-mode WAX poly(DEAEMA-co-DVB) phase containing a tertiary amine with a pKa value of approximately 10.7 could be used for simultaneous clean-up and preconcentration of strongly and weakly acidic organic pollutants in real environmental water, which could not be achieved by single use of quaternary ammonium strong anion-exchange phase or weaker primary and secondary amine anion-exchange.