A molecularly imprinted polymer on chromium (ΙΙΙ) oxide nanoparticles for spectrofluorometric detection of bisphenol A

Construction of a ratiometric electrochemical sensor for Bisphenol A detection by coupling nonionic surfactant-decorated conductive carbon black with ferricyanide probe

In this work, a novel ratiometric electrochemical sensor for bisphenol A (BPA) detection was facilely constructed by coupling conductive carbon black (VXC-72R) with ferricyanide probe. The VXC-72R was decorated with nonionic surfactant Tween to enhance the sensitivity and coated on glassy carbon electrode (GCE), whereas K3[Fe(CN)6] was introduced into electrolyte solution as an internal reference probe to realize dual-signal outputs. The present ratiometric electrochemical sensor achieved a highly sensitive and selective detection of BPA in PBS solution (pH = 7.0), with a linear range of 0.08-40.0 μM and detection limit of 0.05 μM. Moreover, it has been successfully applied to the determination of BPA in real lake water and milk samples with the satisfactory recoveries rates of 94.8-102.3 %.

Immunodetection of Poorly Soluble Substances: Limitations and Their Overcoming

Immunoassays based on the specific antigen-antibody interactions are efficient tools to detect various compounds and estimate their content. Usually, these assays are implemented in water-saline media with composition close to physiological conditions. However, many substances are insoluble or cannot be molecularly dispersed in such media, which objectively creates problems when interacting in aquatic environments. Thus, obtaining immunoreactants and implementing immunoassays of these substances need special methodological solutions. Hydrophobicity of antigens as well as their limited ability to functionalization and conjugation are often overlooked when developing immunoassays for these compounds. The main key finding is the possibility to influence the behavior of hydrophobic compounds for immunoassays, which requires specific approaches summarized in the review. Using the examples of two groups of compounds-surfactants (alkyl- and bisphenols) and fullerenes, we systematized the existing knowledge and experience in the development of immunoassays. This review addresses the challenges of immunodetection of poorly soluble substances and proposes solutions such as the use of hydrotropes, other solubilization techniques, and alternative receptors (aptamers and molecularly imprinted polymers).

Green Prospective Approach of Chromium Zinc Oxide Nanoparticles for Highly Ultrasensitive Electrochemical Detection of Anti-hypotensive Medication in Various Matrices

A highly ultrasensitive sensor that relied on Cr/ZnO-NPs was developed to detect etilefrine hydrochloride (ETF) in different matrices via a particular green voltammetric technique. The X-ray diffraction pattern showed the nanomaterials of the polycrystalline hexagonal structure. The energy-dispersive X-ray spectrum approved the presence of Cr3+ inside the host zinc oxide framework. The morphological and topological characteristics were visualized using transmission electron microscopy and atomic force microscopy micrographs describing the nanoparticles in spherical-like shape with large-surface area. The energy gap (Eg) was evaluated from transmittance (T %) and reflectance (R %) spectra within the visible region. The optimization study indicated that the Cr/ZnO-NP/CPE sensor has high sensitivity, thanks to the distinctive physical and chemical properties of the fabricated electrode. A new approach showed a great selectivity for determining ETF in different matrices in the presence of other interferents like levodopa. Under optimal circumstances, the square-wave voltammetry revealed a linear response to ETF from 0.01 to 10 μmol L-1 (r = 0.9996) with quantification and detection limits of 9.11 and 2.97 nmol L-1, respectively. Finally, the proposed approach was effectively applied to estimate ETF in pharmaceutical dosage forms and biological fluids using simple, accurate, and selective electrochemical electrode. The greenness profile assessment of the developed method was performed using the Eco-Scale and green analytical procedure index. These tools indicated that the proposed method is an eco-friendly technique for the determination of ETF in different matrices.

Preparation of molecularly imprinted ratiometric fluorescence sensor for visual detection of tetrabromobisphenol A in water samples

A sensitive molecularly imprinted ratiometric fluorescence sensor was constructed for the first time to visually detect tetrabromobisphenol A (TBBPA). The blue fluorescent carbon quantum dots (CQDs) were coated with SiO₂ through the reverse microemulsion method to obtain a stable internal reference signal CQDs@SiO₂. The ratiometric fluorescence sensor was finally prepared using red fluorescent CdTe QDs as the response signal in the presence of CQDs@SiO₂. When the molecularly imprinted polymers were combined with TBBPA, the fluorescence of CdTe QDs (Ex = 365 nm, Em = 665 nm) was rapidly quenched, while that of CQDs (Ex = 365 nm, Em = 441 nm) remained stable, resulting in a noticeable fluorescence color change. Moreover, the fluorescence intensity ratio (I₆₆₅/I₄₄₁)₀/(I₆₆₅/I₄₄₁) of the sensor showed a linear response to TBBPA in the concentration range 0.1 to 10 μM with a low detection limit of 3.8 nM. The prepared sensor was successfully applied to detect TBBPA in water samples. The recoveries were in the range 98.2-103%, with relative standard deviations lower than 2.5%. Furthermore, a fluorescent test strip for visual monitoring of TBBPA was constructed to streamline the procedure. The excellent results demonstrate that the prepared test strip has a broad prospect for the offline detection of pollutants.

Imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extraction coupled with high performance liquid chromatography for analysis of bisphenol A

An effective method based on an imidazole ionic liquid functionalized ZIF-67 molecularly imprinted solid-phase extractant (ZIF-67@[Bmim][Br]@MIP) coupled with high performance liquid chromatography (HPLC) for the separation/analysis of bisphenol A (BPA) was established. ZIF-67@[Bmim][Br]@MIP was characterized by FTIR, XRD, SEM, TEM and BET. Several important factors, such as pH, amount of extractant, extraction time, and types of eluents were investigated in detail. Under the optimal conditions, the linear range of the method was 0.01-20.00 μg mL^-1, the detection limit was 5.0 ng mL^-1, and the linear correlation was good (R² = 0.9994). The detection of BPA in mineral water bottles, milk cartons and milk tea cups proved that the method was simple and effective, and could be used to separate and analyze BPA in real samples.

Precipitation Polymerization: A Powerful Tool for Preparation of Uniform Polymer Particles

Precipitation polymerization (PP) is a powerful tool to prepare various types of uniform polymer particles owing to its outstanding advantages of easy operation and the absence of any surfactant. Several PP approaches have been developed up to now, including traditional thermo-induced precipitation polymerization (TRPP), distillation precipitation polymerization (DPP), reflux precipitation polymerization (RPP), photoinduced precipitation polymerization (PPP), solvothermal precipitation polymerization (SPP), controlled/‘‘living’’ radical precipitation polymerization (CRPP) and self-stabilized precipitation polymerization (2SPP). In this review, a general introduction to the categories, mechanisms, and applications of precipitation polymerization and the recent developments are presented, proving that PP has great potential to become one of the most attractive polymerization techniques in materials science and bio-medical areas.

A Fluorimetric Method Based On Magnetic Molecularly Imprinted Polymer For Selective Detection Of Chlorferon

In the present work, reusable magnetic molecularly imprinted polymers have been used for the first time as an adsorbent for the determination of chlorferon. Magnetic molecularly imprinted polymers have been used for the selective separation of chlorferon from the solution and sensitive fluorimetric determination has been performed using the native fluorescence of chlorferon. The developed method is rapid and determination of chlorferon was completed in an hour. Limit of detection (LOD) of the method was found to be 0.0027 µM and the linearity of the calibration graph was observed within the range of 0.01-0.36 µM (2.5 - 75 µg L^-1). Adsorption isotherms point out the multilayer adsorption and the heterogeneous distribution of binding sites for imprinted polymer and homogeneous binding site for non-imprinted polymer. The adsorption capacities of imprinted polymer and non-imprinted polymer were calculated as 2.03 μmol g^-1 and 0.96 μmol g^-1, respectively and the imprinting factor was found to be 2.11. The interference effects of some organic compounds and characterization studies were also evaluated. The method has been applied to honey and tap water samples and the recoveries were found to be in the range of 91.3 and 101.1 %.

Application of Molecularly Imprinted Polymers in the Analysis of Waters and Wastewaters

The increase of the global population and shortage of renewable water resources urges the development of possible remedies to improve the quality and reusability of waste and contaminated water supplies. Different water pollutants, such as heavy metals, dyes, pesticides, endocrine disrupting compounds (EDCs), and pharmaceuticals, are produced through continuous technical and industrial developments that are emerging with the increasing population. Molecularly imprinted polymers (MIPs) represent a class of synthetic receptors that can be produced from different types of polymerization reactions between a target template and functional monomer(s), having functional groups specifically interacting with the template; such interactions can be tailored according to the purpose of designing the polymer and based on the nature of the target compounds. The removal of the template using suitable knocking out agents renders a recognition cavity that can specifically rebind to the target template which is the main mechanism of the applicability of MIPs in electrochemical sensors and as solid phase extraction sorbents. MIPs have unique properties in terms of stability, selectivity, and resistance to acids and bases besides being of low cost and simple to prepare; thus, they are excellent materials to be used for water analysis. The current review represents the different applications of MIPs in the past five years for the detection of different classes of water and wastewater contaminants and possible approaches for future applications.