Molecularly Imprinted Polymers as Extracting Media for the Chromatographic Determination of Antibiotics in Milk

Electrospinning and Rheological Characterization of Polyethylene Terephthalate and Polyvinyl Alcohol with Different Degrees of Hydrolysis Incorporating Molecularly Imprinted Polymers

This study investigates the electrospinning and rheological properties of polyethylene terephthalate (PET) and polyvinyl alcohol (PVA) with varying degrees of hydrolysis (DH) for molecularly imprinted polymer (MIP) incorporation. The morphology and properties of the electrospun nanofibers were evaluated, revealing that PVA nanofibers exhibited smoother and more uniform structures compared to PET fibers. The rheological behavior of the polymer solutions was also characterized, showing that PVA 99 DH solution exhibited shear-thinning behavior due to the unique structural properties of the polymer chains. The introduction of MIP and NIP additives had no significant impact on the rheological properties, except for PVA 99 MIP and NIP solutions, which showed deviations from Newtonian behavior. The electrospun MIP nanofibers showed a conductivity of 1054 µS/cm for PVA (87-90% DH) and a viscosity of 165.5 mPa·s, leading to optimal fiber formation, while displaying a good adsorption capacity of 0.36 mg for PVA-MIP to effectively target pharmaceuticals such as emtricitabine and tenofovir disoproxil, showing their potential for advanced water treatment applications. The results suggest that the electrospinning process and rheological properties of the polymer solutions are influenced by the molecular structure and interactions within the polymer matrix, which can be exploited to tailor the properties of MIPs for specific applications.

Advances in Bioreceptor Layer Engineering in Nanomaterial-based Sensing of Pseudomonas Aeruginosa and its Metabolites

Pseudomonas aeruginosa is a pathogen that infects wounds and burns and causes severe infections in immunocompromised humans. The high virulence, the rise of antibiotic-resistant strains, and the easy transmissibility of P. aeruginosa necessitate its fast detection and control. The gold standard for detecting P. aeruginosa, the plate culture method, though reliable, takes several days to complete. Therefore, developing accurate, rapid, and easy-to-use diagnostic tools for P. aeruginosa is highly desirable. Nanomaterial-based biosensors are at the forefront of detecting P. aeruginosa and its secondary metabolites. This review summarises the biorecognition elements, biomarkers, immobilisation strategies, and current state-of-the-art biosensors for P. aeruginosa. The review highlights the underlying principles of bioreceptor layer engineering and the design of optical, electrochemical, mass-based, and thermal biosensors based on nanomaterials. The advantages and disadvantages of these biosensors and their future point-of-care applications are also discussed. This review outlines significant advancements in biosensors and sensors for detecting P. aeruginosa and its metabolites. Research efforts have identified biorecognition elements specific and selective towards P. aeruginosa. The stability, ease of preparation, cost-effectiveness, and integration of these biorecognition elements onto transducers are pivotal for their application in biosensors and sensors. At the same time, when developing sensors for clinically significant analytes such as P. aeruginosa, virulence factors need to be addressed, such as the sensor's sensitivity, reliability, and response time in samples obtained from patients. The point-of-care applicability of the developed sensor may be an added advantage since it enables onsite determination. In this context, optical methods developed for P. aeruginosa offer promising potential.

Detection and quantification of antibiotic residues in goat milk in Mahikeng Local Municipality

Goat milk could be used to reduce malnutrition since it is highly nutritious, and many people in rural communities in South Africa rear small ruminants for survival. However, the risk of food contamination by antibiotic residues is one of the significant problems facing public health, and is a result of the irresponsible use of veterinary drugs. One hundred goat farmers were interviewed using a questionnaire, and raw milk samples from 266 goats were collected and analysed for the presence of antibiotic residues. Screening for amoxicillin, tetracycline, sulfamethazine, erythromycin, and streptomycin residues was done using the enzymelinked immunosorbent assay (ELISA) while high-performance liquid chromatography (HPLC) was carried out for confirmation. The questionnaire shows that all (100%) of the participants acknowledged the use of antibiotics on their goats and 99% of them were aware of the possibility of antibiotic residues in milk. ELISA results for residues of erythromycin, sulfamethazine and amoxicillin exceeded the Codex Alimentarius maximum residue levels (MRLs) in 94.7%, 82.3%, and 35.3% of analysed samples, respectively. Tetracycline was present in all (100%) analysed milk samples, and streptomycin was detected in 18.7% of samples; however, these results were below the recommended MRLs. The HPLC method confirmed the presence of streptomycin and tetracycline residues in 90% and 40% of the samples analysed. However, the concentrations were below the accepted MRL standards. Approximately 76.6% of samples exceeded the established MRL for sulfamethazine and 10% for erythromycin. Amoxicillin was not detected by the HPLC method. The results obtained in this study indicate a high level of contamination of goat milk with antibiotic residues, which may harm the health of the consumers.

Advancements and greenification potential of magnetic molecularly imprinted polymers for chromatographic analysis of veterinary drug residues in milk

Milk, as a widely consumed nutrient-rich food, is crucial for bone health, growth, and overall nutrition. The persistent application of veterinary drugs for controlling diseases and heightening milk yield has imparted substantial repercussions on human health and environmental ecosystems. Due to the high demand, fresh consumption, complex composition of milk, and the potential adverse impacts of drug residues, advanced greener analytical methods are necessitated. Among them, functional materials-based analytical methods attract wide concerns. The magnetic molecularly imprinted polymers (MMIPs), as a kind of typical functional material, possess excellent greenification characteristics and potencies, and they are easily integrated into various detection technologies, which have offered green approaches toward analytes such as veterinary drugs in milk. Despite their increasing applications and great potential, MMIPs' use in dairy matrices remains underexplored, especially regarding ecological sustainability. This work reviews recent advances in MMIPs' synthesis and application as efficient sorbents for veterinary drug extraction in milk followed by chromatographic analysis. The uniqueness and effectiveness of MMIPs in real milk samples are evaluated, current limitations are addressed, and greenification opportunities are proposed. MMIPs show promise in revolutionizing green analytical procedures for veterinary drug detection, aligning with the environmental goals of modern food production systems.

Emerging trends in sensors based on molecular imprinting technology: Harnessing smartphones for portable detection and recognition

Molecular imprinting technology (MIT) has become a promising recognition technology in various fields due to its specificity, high efficiency, stability and eco-friendliness in the recognition of target. Molecularly imprinted polymers (MIPs), known as 'artificial receptors', are shown similar properties to natural receptors as a biomimetic material. The selectivity of recognition for targets can be greatly improved when MIPs are introduced into sensors, as known that MIPs, are suitable for the pretreatment and analysis of trace substances in complex matrix samples. At present, various sensors has been developed by the combination with MIPs for detecting and identifying trace compounds, biological macromolecules or other substances, such as optical, electrochemical and piezoelectric sensors. Smart phones, with their built-in sensors and powerful digital imaging capabilities, provide a unique platform for the needs of portability and instant detection. MIP sensors based on smart phones are expected to become a new research direction in the future. This review discusses the latest applications of MIP sensors in the field of detection and recognition in recent years, summarizes the frontier progress of MIP sensor research based on smart phones in the past two years, and points out the challenges, limitations and future development prospects.

Sonocatalytic degrading antibiotics over activated carbon in cow milk

Herein, an efficient, simple and economical approach to remove antibiotics (ABX), i.e. ceftiofur hydrochloride, sulfamonomethoxine sodium (SMM), marbofloxacin and oxytetracycline by sonication with activated carbon (AC) from cow milk has been successfully implemented. The pseudo-first-order kinetics constants for the sonolytic and sonocatalytic degrading SMM are 0.036 and 0.093 min-1, respectively. The synergistic efficiency of removing ABX by using sonocatalysis reached 1.8-4.0. Hydrophobic ABX underwent faster degradation than hydrophilic ABX in sonocatalytic systems. Adding 0.5 mmol L-1 H2O2, the optimal concentration, improved the sonocatalytic degradation rates of ABX by 9.1%-28.5%. Surface area and dose of AC play crucial roles in the sonocatalysis of ABX. By sonicating 50 mL of 5.52 μmol L-1 ABX in milk at 500 kHz and 259 W with 20 mg AC for 20-60 min resulted in residual ABX concentrations ranging from 42.6 to 95.1 μg L-1, which meet the relative maximum residue limits set by European Commission.

Development and Characterization of a Molecularly Imprinted Polymer for the Selective Removal of Brilliant Green Textile Dye from River and Textile Industry Effluents

In this paper, we present an alternative technique for the removal of Brilliant Green dye (BG) in aqueous solutions based on the application of molecularly imprinted polymer (MIP) as a selective adsorbent for BG. The MIP was prepared by bulk radical polymerization using BG as the template; methacrylic acid (MAA) as the functional monomer, selected via computer simulations; ethylene glycol dimethacrylate (EGDMA) as cross-linker; and 2,2'-azobis(2-methylpropionitrile) (AIBN) as the radical initiator. Scanning electron microscopy (SEM) analyses of the MIP and non-molecularly imprinted polymer (NIP)-used as the control material-showed that the two polymers exhibited similar morphology in terms of shape and size; however, N2 sorption studies showed that the MIP displayed a much higher BET surface (three times bigger) compared to the NIP, which is clearly indicative of the adequate formation of porosity in the former. The data obtained from FTIR analysis indicated the successful formation of imprinted polymer based on the experimental procedure applied. Kinetic adsorption studies revealed that the data fitted quite well with a pseudo-second order kinetic model. The BG adsorption isotherm was effectively described by the Langmuir isotherm model. The proposed MIP exhibited high selectivity toward BG in the presence of other interfering dyes due to the presence of specific recognition sites (IF = 2.53) on its high specific surface area (112 m2/g). The imprinted polymer also displayed a great potential when applied for the selective removal of BG in real river water samples, with recovery ranging from 99 to 101%.

Modification of Cotton Fabric with Molecularly Imprinted Polymer-Coated Carbon Dots as a Sensor for 17 α-methyltestosterone

Molecularly imprinted polymers@ethylenediamine-modified carbon dots grafted on cotton fabrics (MIPs@EDA-CDs/CF) and smartphone-based fluorescence image analysis were proposed and used for the first time for the detection of 17 α-methyltestosterone (MT). The EDA-CDs were synthesized and grafted on cotton fabric before coating with the MIPs. The MIPs were synthesized using the MT as a template molecule, methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, and azobisisobutyronitrile (AIBN) as an initiator. The MIPs@EDA-CDs/CF were characterized using FTIR, SEM-EDS, and RGB fluorescence imaging. The fluorescence images were also taken using a smartphone and the ImageJ program was used for RGB measurement. The Δ red intensity was linearly proportional to MT concentration in the range of 100 to 1000 μg/L (R2 = 0.999) with a detection limit of 44.4 μg/L and quantification limit of 134 μg/L. The MIPs@EDA-CDs/CF could be stored at 4 °C for a few weeks and could be reused twice. The proposed method could apply for the specific determination of MT in water and sediment samples along with satisfactory recoveries of 96-104% and an acceptable relative standard deviation of 1-6% at the ppb level.

Determination of trace antibiotics in water and milk via preconcentration and cleanup using activated carbons

CPAC-SPE-HPLC (coconut powdered activated carbon -SPE- HPLC) has been developed for the determination of antibiotic (ABX), sulfamonomethoxine sodium (SMM), oxytetracycline (OTC), ceftiofur hydrochloride (CEF) and marbofloxacin (MAR), in water and milk. Over 99.0% SMM and OTC were recovered from 20 mL of 0.5 μg/mL ABX solution using 10 mg-CPAC for adsorption and 2 mL of 30% NH₄OH/EtOH (1/19 v/v) for elution. Similarly, over 99.0% CEF and MAR were recovered using 15 mg-CPAC and 2 mL of 30% NH₄OH/n-PrOH (1/19 v/v). Moreover, the recovery efficiencies of various ABX from 5 to 80 mL of 0.02-2.00 μg/mL medicated milk containing 10 mM EDTA are ordered as follows: OTC (99.3%), SMM (99.1%) > CEF (68.9%) > MAR (61.4%). No interference towards HPLC analysis were observed with elution using 2 mL of 30% NH₄OH/EtOH (1/19 v/v). Furthermore, much lower limit of detections (0.02 μg/mL) than the maximum residual limits from European Commission (0.075-0.100 μg/mL) were obtained.

Advances in Detection of Antibiotic Pollutants in Aqueous Media Using Molecular Imprinting Technique-A Review

Antibiotics constitute one of the emerging categories of persistent organic pollutants, characterised by their expansion of resistant pathogens. Antibiotic pollutants create a major public health challenge, with already identifiable detrimental effects on human and animal health. A fundamental aspect of controlling and preventing the spread of pollutants is the continuous screening and monitoring of environmental samples. Molecular imprinting is a state-of-the-art technique for designing robust biomimetic receptors called molecularly imprinted polymers (MIPs), which mimic natural biomolecules in target-selective recognition. When integrated with an appropriate sensor transducer, MIP demonstrates a potential for the needed environmental monitoring, thus justifying the observed rise in interest in this field of research. This review examines scientific interventions within the last decade on the determination of antibiotic water pollutants using MIP receptors interfaced with label-free sensing platforms, with an expanded focus on optical, piezoelectric, and electrochemical systems. Following these, the review evaluates the analytical performance of outstanding MIP-based sensors for environmentally significant antibiotics, while highlighting the importance of computational chemistry in functional monomer selection and the strategies for signal amplification and performance improvement. Lastly, the review points out the future trends in antibiotic MIP research, as it transits from a proof of concept to the much demanded commercially available entity.

On the use of metal-organic frameworks for the extraction of organic compounds from environmental samples

The determination of trace metals and organic contaminants in environmental samples, such as water, air, soil, and sediment, is until today a challenging process for the analytical chemistry. Metal-organic frameworks (MOFs) are novel porous nanomaterials that are composed of metal ions and an organic connector. These materials are gaining more and more attention due to their superior characteristics, such as high surface area, tunable pore size, mechanical and thermal stability, luminosity, and charge transfer ability between metals and ligands. Among the various applications of MOFs are gas storage, separation, catalysis, and drug delivery. Recently, MOFs have been successfully introduced in the field of sample preparation for analytical chemistry and they have been used for sample pretreatment of various matrices. This review focuses on the applications of MOFs as novel adsorbents for the extraction of organic compounds from environmental samples.

Solid-Phase Extraction of Active Compounds from Natural Products by Molecularly Imprinted Polymers: Synthesis and Extraction Parameters

Molecularly imprinted polymers (MIPs) are synthetic polymers with a predetermined selectivity for a particular analyte or group of structurally related compounds, making them ideal materials for separation processes. Hence, in sample preparation, MIPs are chosen as an excellent material to provide selectivity. Moreover, its use in solid-phase extraction, also referred to as molecular imprinted solid phase extraction (MISPE), is well regarded. In recent years, many papers have been published addressing the utilization of MIPs or MISPE as sorbents in natural product applications, such as synthesis. This review describes the synthesis and characterization of MIPs as a tool in natural product applications.

Factors Affecting Preparation of Molecularly Imprinted Polymer and Methods on Finding Template-Monomer Interaction as the Key of Selective Properties of the Materials

Molecular imprinting is a technique for creating artificial recognition sites on polymer matrices that complement the template in terms of size, shape, and spatial arrangement of functional groups. The main advantage of Molecularly Imprinted Polymers (MIP) as the polymer for use with a molecular imprinting technique is that they have high selectivity and affinity for the target molecules used in the molding process. The components of a Molecularly Imprinted Polymer are template, functional monomer, cross-linker, solvent, and initiator. Many things determine the success of a Molecularly Imprinted Polymer, but the Molecularly Imprinted Polymer component and the interaction between template-monomers are the most critical factors. This review will discuss how to find the interaction between template and monomer in Molecularly Imprinted Polymer before polymerization and after polymerization and choose the suitable component for MIP development. Computer simulation, UV-Vis spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), Proton-Nuclear Magnetic Resonance (¹H-NMR) are generally used to determine the type and strength of intermolecular interaction on pre-polymerization stage. In turn, Suspended State Saturation Transfer Difference High Resolution/Magic Angle Spinning (STD HR/MAS) NMR, Raman Spectroscopy, and Surface-Enhanced Raman Scattering (SERS) and Fluorescence Spectroscopy are used to detect chemical interaction after polymerization. Hydrogen bonding is the type of interaction that is becoming a focus to find on all methods as this interaction strongly contributes to the affinity of molecularly imprinted polymers (MIPs).

Automated Solid Phase Extraction of Cd(II), Co(II), Cu(II) and Pb(II) Coupled with Flame Atomic Absorption Spectrometry Utilizing a New Sol-Gel Functionalized Silica Sorbent

In this study a simple and sensitive on-line sorbent extraction platform coupled with flame atomic absorption spectrometry for trace metals determination was developed. The system utilized for the first time a novel sol-gel thiocyanatopropyl functionalized silica as adsorbent for metal’s separation and preconcentration. The main factors affecting the performance of the on-line system were investigated and optimized. The effect of potential interfering species that occur naturally in environmental and biological samples, as well as some toxic elements, was evaluated. Under optimum conditions the enhancement factors ranged between 73 and 152 for the target analytes. The LODs of the proposed methods were 0.15 μg L−1 for Cd(II), 0.5 μg L−1 for Co(II), 0.5 μg L−1 for Cu(II) and 1.9 μg L−1 for Pb(II) for 120 s preconcentration time. The relative standard deviation values for all elements were less than 3.8%, indicating good method precision. Moreover, the sol-gel thiocyanatopropyl functionalized silica-packed microcolumns exhibited limited flow resistance and excellent packing reproducibility. Finally, the proposed method was utilized for the analysis of environmental and biological samples.

Recent advances in the extraction of triazine herbicides from water samples

Pesticides are excessively used in agriculture to improve the quality of crops by eliminating the negative effects of pests. Among the different groups of pesticides, triazine pesticides are a group of compounds that contain a substituted C₃ H₃ N₃ heterocyclic ring, and they are widely used. Triazine pesticides can be dangerous for humans as well as for the aquatic environment because of their high toxicity and endocrine disrupting effect. However, the concentration of these chemical compounds in water samples is low. Moreover, other compounds that may exist in the water samples can interfere with the determination of triazine pesticides. As a result, it is important to develop sample preparation methods that provide preconcentration of the target analyte and sufficient clean-up of the samples. Recently, a wide variety of novel microextraction and miniaturized extraction techniques (e.g., solid-phase microextraction and liquid-phase microextraction, stir bar sorptive extraction, fabric phase sorptive extraction, dispersive solid-phase extraction, and magnetic solid-phase extraction) have been developed. In this review, we aim to discuss the recent advances regarding the extraction of triazine pesticides from environmental water samples. Emphasis will be given to novel sample preparation methods and novel sorbents developed for sorbent-based extraction techniques.

Metal-Organic Frameworks in Bioanalysis: Extraction of Small Organic Molecules

The quantitative determination of xenobiotic compounds, as well as biotics in biological matrices, is generally described with the term bioanalysis. Due to the complexity of biofluids, in combination with the low concentration of the small molecules, their determination in biological matrices is a challenging procedure. Apart from the conventional solid-phase extraction, liquid-liquid extraction, protein precipitation, and direct injection approaches, nowadays, a plethora of microextraction and miniaturized extraction techniques have been reported. Furthermore, the development and evaluation of novel extraction adsorbents for sample preparation has become a popular research field. Metal-organic frameworks (MOFs) are novel materials composed of metal ions or clusters in coordination with organic linkers. Unequivocally, MOFs are gaining more and more attention in analytical chemistry due to their superior properties, including high surface area and tunability of pore size and functionality. This review discusses the utilization of MOFs in the sample preparation of biological samples for the green extraction of small organic molecules. Their common preparation and characterization strategies are discussed, while emphasis is given to their applications for green sample preparation.

Green bioanalytical sample preparation: fabric phase sorptive extraction

Fabric phase sorptive extraction (FPSE) is a recently introduced sample preparation technique that has attracted substantial interest of the scientific community dealing with bioanalysis. This technique is based on a permeable and flexible substrate made of fabric, coated with a sol-gel organic-inorganic sorbent. Among the benefits of FPSE are its tunable selectivity, adjustable porosity, minimized sample preparation workflow, substantially reduced organic solvent consumption, rapid extraction kinetics and superior extraction efficiency, many of which are well-known criteria for Green Analytical Chemistry. As such, FPSE has established itself as a leading green sample preparation technology of 21st century. In this review, we discuss the principal steps for the development of an FPSE method, the main method optimization strategies, as well as the applications of FPSE in bioanalysis for the extraction of a wide range of analytes (e.g., estrogens, benzodiazepines, androgens and progestogens, penicillins, anti-inflammatory drugs, parabens etc.).

Preparation of monodisperse, restricted-access, media-molecularly imprinted polymers using bi-functional monomers for solid-phase extraction of sarafloxacin from complex samples

Monodisperse restricted-access media bi-functional monomers with molecularly imprinted polymers (RAM-MIPs) were constructed using surface-initiated atom transfer radical polymerization. They were used as solid-phase extraction (SPE) adsorbents to enrich sarafloxacin (SAR) residues from egg samples, and influences on their performance were investigated. Optimum synthesis of RAM-MIPs was achieved by combining a bi-functional monomer (4-vinylpyridine-co-methacrylic acid, 1:3) with an 8:1:32:8 ratio of a template molecule, cross-linker, and restricted-access functional monomer. The SAR imprinting factor of RAM-MIPs was 6.05 and the selectivity coefficient between SAR and other fluoroquinolones was 1.86-2.64. Compared with traditional MIPs, the RAM-MIPs showed better SAR enrichment and selectivity during extraction of a complex protein-containing solution. Empty SPE cartridges were filled with RAM-MIP microspheres as SPE adsorbents. The limit of quantitation for SAR was 4.23 ng g^-1 (signal-to-noise ratio = 10) and the mean SAR recovery from spiked egg samples was 94.0-101.3%. Intra-day and inter-day relative standard deviations were 1.1-9% and 1.5-3.3%, respectively.

Magnetic solid-phase extraction of caffeine from surface water samples with a micro–meso porous activated carbon/Fe3O4 nanocomposite prior to its determination by GC-MS

A novel micro–meso porous activated carbon/Fe₃O₄ (Bm) composite was synthesized from the active charcoal precursor BAX-1500 and used in the magnetic solid-phase extraction (MSPE) of caffeine prior to its determination by gas chromatography-mass spectrometry (GC-MS). The main factors affecting the extraction and desorption steps of the MSPE procedure were investigated and optimized. These factors include extraction time, sorbent mass and salt addition for the adsorption step and type of eluent, desorption time and volume of desorption solution for the desorption step. Under optimum conditions, the absolute extraction recovery was found to be 91.1% and good linearity was observed in the investigated concentration range of 0.6–12.5 ng mL⁻¹ (R² = 0.9997). The limit of detection was 0.18 ng mL⁻¹ and the limit of quantification was 0.60 ng mL⁻¹. The method was successfully applied to the analysis of surface water samples. The proposed MSPE method is simple, rapid, sensitive and environmentally friendly.

A novel magnetic solid phase material based on a micro–meso porous activated carbon/Fe₃O₄ nanocomposite was used to extract caffeine from surface water samples. The method is efficient and rapid, and has minimum solvent consumption.

Dietary Exposure Assessment of Veterinary Antibiotics in Pork Meat on Children and Adolescents in Cyprus

In recent years, huge amounts of antibiotics have been administered to farm animals, and as a result, residues of these antibiotics can accumulate in livestock products and, once consumed, may be transmitted to humans. Farm animals' antibiotic treatment may therefore present a risk for consumers health, especially for children and adolescents. In children, the immune system is not fully developed, and thus, they are more susceptible than adults to resistant bacteria. A dietary exposure assessment was conducted on veterinary antibiotics found in raw pork meat among children and adolescents in Cyprus, since pork is the most consumed red meat in Cypriot population. The study was based on the results of the occurrence of 45 residual antibiotics in raw pork meat samples in Cyprus between 2012 and 2017 in combination with data on the consumption of pork meat on children and adolescents taken from the latest demographic report in Cyprus. Estimated daily intake (EDI) values of veterinary antibiotics for children aged 6-9 years old, were higher compared to EDI values for adolescents aged 10-17 years old. The percentage ratio of the estimated daily intake to the acceptable daily intake for all the veterinary antibiotic residues was less than 5.6. The results indicate that antibiotic residues in pork meat of inland production are below the acceptable daily intake and are of low risk to human health related to the exposure of antibiotics. Nevertheless, continuous exposure to low levels of antibiotic residues in respect to age vulnerability should be of a great concern.

Employing molecularly imprinted polymers in the development of electroanalytical methodologies for antibiotic determination

Antibiotics, although being amazing compounds, need to be monitored in the environment and foodstuff. This is primarily to prevent the development of antibiotic resistance that may make them ineffective. Unsurprisingly, advances in analyticalsciences that can improve their determination are appreciated. Electrochemical techniques are known for their simplicity, sensitivity, portability and low-cost; however, they are often not selective enough without recurring to a discriminating element like an antibody. Molecular imprinting technology aims to create artificial tissues mimicking antibodies named molecularly imprinted polymers (MIPs), these retain the advantages of selectivity but without the typical disadvantages of biological material, like limited shelf-life and high cost. This manuscript aims to review all analytical methodologies for antibiotics, using MIPs, where the detection technique is electrochemical, like differential pulse voltammetry (DPV), square-wave voltammetry (SWV) or electrochemical impedance spectroscopy (EIS). MIPs developed by electropolymerization (e-MIPs) were applied in about 60 publications and patents found in the bibliographic search, while MIPs developed by other polymerization techniques, like temperature assisted ("bulk") or photopolymerization, were limited to around 40. Published works covered the electroanalysis of a wide range of different antibiotics (β-lactams, tetracyclines, quinolones, macrolides, aminoglycosides, among other), in a wide range of matrices (food, environmental and biological).

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Bioanalytical HPLC Applications of In-Tube Solid Phase Microextraction: A Two-Decade Overview

In-tube solid phase microextraction is a cutting-edge sample treatment technique offering significant advantages in terms of miniaturization, green character, automation, and preconcentration prior to analysis. During the past years, there has been a considerable increase in the reported publications, as well as in the research groups focusing their activities on this technique. In the present review article, HPLC bioanalytical applications of in-tube SPME are discussed, covering a wide time frame of twenty years of research reports. Instrumental aspects towards the coupling of in-tube SPME and HPLC are also discussed, and detailed information on materials/coatings and applications in biological samples are provided.

Molecular-Imprinting-Based Surface-Enhanced Raman Scattering Sensors

Molecularly imprinted polymers (MIPs) receive extensive interest, owing to their structure predictability, recognition specificity, and application universality as well as robustness, simplicity, and inexpensiveness. Surface-enhanced Raman scattering (SERS) is regarded as an ideal optical detection candidate for its unique features of fingerprint recognition, nondestructive property, high sensitivity, and rapidity. Accordingly, MIP based SERS (MIP-SERS) sensors have attracted significant research interest for versatile applications especially in the field of chemo- and bioanalysis, showing excellent identification and detection performances. Herein, we comprehensively review the recent advances in MIP-SERS sensors construction and applications, including sensing principles and signal enhancement mechanisms, focusing on novel construction strategies and representative applications. First, the basic structure of the MIP-SERS sensors is briefly outlined. Second, novel imprinting strategies are highlighted, mainly including multifunctional monomer imprinting, dummy template imprinting, living/controlled radical polymerization, and stimuli-responsive imprinting. Third, typical application of MIP-SERS sensors in chemo/bioanalysis is summarized from both small and macromolecular aspects. Lastly, the challenges and perspectives of the MIP-SERS sensors are proposed, orienting sensitivity improvement and application expanding.

Facile and efficient removal of Pb(II) from aqueous solution by chitosan-lead ion imprinted polymer network

A new chitosan based imprinted polymer was prepared by copolymerization of 4-Vinylpyridine (VP) as a functional monomer and N,N'-Methylenebisacrylamide (MBA) as a crosslinker in the presence of Potassium peroxodisulfate (KPS) as an initiator to eliminate Pb(II) from aqueous solutions. The template ions were removed from ion imprinted polymer (IIPs) particles by leaching with 0.1 M nitric acid (HNO₃) that leaves cavities in the particles with the capability of selective extraction of the Pb(II) ions. Some properties of the bioadsorbent were further identified using Field Emission Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Thermal Gravimetric Analysis (TGA). In addition, the equilibrium adsorption data were examined through Langmuir and Freundlich isotherm models and it was found that adsorption data fit well with the Freundlich isotherm. The competitive adsorption studies clearly showed that the Pb(II)-IP has a much higher adsorption capacity for Pb(II) than the non-imprinted polymer (NIP) with the same chemical composition; furthermore, it has excellent selectivity for the targeted ion. In addition, the studies regarding the regeneration and reuse studies revealed that the Pb(II)-IP beads showed no significant decrease in their adsorption capacities.

Determination of sulfamerazine in aquatic products by molecularly imprinted capillary electrochromatography

A molecularly imprinted monolith was prepared and evaluated for the special selective separation of sulfamerazine (SMR) by capillary electrochromatography (CEC). The single-step in situ polymerization method was applied through thermally immobilized vinyl groups of itaconic acid and a derivatization capillary column using SMR as the template. The monolith with optimal selectivity and permeability was performed at 45°C for 7 h according to the molar ratios of 1 : 4 : 10 (template/functional monomer/cross-linker). Under the optimized separation conditions of 75% acetonitrile in 20 mM phosphate buffer with pH 5.0, 15 kV applied voltage and 20°C column temperature, the imprinted monolith showed strong recognition ability for SMR and high column performance. Finally, the molecularly imprinted monolith coupled with the CEC method was successfully developed for the quantification of SMR in aquatic products, which was properly validated by a good linear relationship, recoveries and limit of detection. The coupling technique of the molecularly imprinted technology and CEC achieved pre-treatment enrichment and separation analysis in only one miniaturized chromatographic column.

Chiral Stationary Phases for Liquid Chromatography: Recent Developments

The planning and development of new chiral stationary phases (CSPs) for liquid chromatography (LC) are considered as continuous and evolutionary issues since the introduction of the first CSP in 1938. The main objectives of the development strategies were to attempt the improvement of the chromatographic enantioresolution performance of the CSPs as well as enlarge their versatility and range of applications. Additionally, the transition to ultra-high-performance LC were underscored. The most recent strategies have comprised the introduction of new chiral selectors, the use of new materials as chromatographic supports or the reduction of its particle size, and the application of different synthetic approaches for preparation of CSPs. This review gathered the most recent developments associated to the different types of CSPs providing an overview of the relevant advances that are arising on LC.

Preparation of lysozyme-imprinted nanoparticles on polydopamine-modified titanium dioxide using ionic liquid as a stabilizer

Molecular imprinting of proteins has evolved into an efficient approach for protein recognition and separation. However, maintaining the structural stability of proteins during the preparation process of molecularly imprinted polymers (MIPs) remains challenging. Ionic liquids (ILs), being capable of maintaining the stability of proteins, might enable effective imprinting and accurate recognition of proteins. In this study, lysozyme (Lyz)-imprinted titanium dioxide (TiO₂) nanoparticles, TiO₂@Lyz-MIPs, have been successfully prepared for selective recognition and separation of Lyz. This was achieved by the free radical polymerization of hydroxyethyl acrylate (HEA) and poly(ethylene glycol) dimethacrylate (PEGDMA) on polydopamine (PDA)-modified TiO₂ nanoparticles using an IL, choline dihydrogen phosphate (chol dhp), as the stabilizer of Lyz. It was found that both PDA modification of TiO₂ and the use of chol dhp as stabilizer improved the adsorption capacity of TiO₂@Lyz-MIPs toward Lyz. When the concentration of HEA was 7 mg mL⁻¹, the ratio of monomer to crosslinker was 20 : 1, and the concentration of chol dhp was 12.5 mg mL⁻¹, the highest imprinting factor of 4.40 was achieved. TiO₂@Lyz-MIPs exhibited relatively high adsorption capacity with the maximum adsorption capacity up to 120 mg g⁻¹, which was more than four times higher than that of the non-imprinted polymers (NIPs) counterpart, TiO₂@Lyz-NIPs. The adsorption rate of Lyz by TiO₂@Lyz-MIPs was also much higher than that of TiO₂@Lyz-NIPs. TiO₂@Lyz-MIPs could successfully separate Lyz from diluted egg white, a complex mixture of proteins. Findings from this study indicate that effective recognition cavities toward Lyz were formed on the surface of Lyz-imprinted TiO₂ nanoparticles prepared using IL as the template stabilizer. This approach may facilitate the development of MIPs for efficient protein recognition and separation.

Molecular imprinting of proteins has evolved into an efficient approach for protein recognition and separation.

Applications of Metal-Organic Frameworks in Food Sample Preparation

Food samples such as milk, beverages, meat and chicken products, fish, etc. are complex and demanding matrices. Various novel materials such as molecular imprinted polymers (MIPs), carbon-based nanomaterials carbon nanotubes, graphene oxide and metal-organic frameworks (MOFs) have been recently introduced in sample preparation to improve clean up as well as to achieve better recoveries, all complying with green analytical chemistry demands. Metal-organic frameworks are hybrid organic inorganic materials, which have been used for gas storage, separation, catalysis and drug delivery. The last few years MOFs have been used for sample preparation of pharmaceutical, environmental samples and food matrices. Due to their high surface area MOFs can be used as adsorbents for the development of sample preparation techniques of food matrices prior to their analysis with chromatographic and spectrometric techniques with great performance characteristics.