Highly sensitive and selective determination of melamine in milk using glassy carbon electrode modified with molecularly imprinted copolymer

Electrochemical Sensors Based on the Electropolymerized Natural Phenolic Antioxidants and Their Analytical Application

The design and fabrication of novel electrochemical sensors with high analytical and operational characteristics are one of the sustainable trends in modern analytical chemistry. Polymeric film formation by the electropolymerization of suitable monomers is one of the methods of sensors fabrication. Among a wide range of the substances able to polymerize, the phenolic ones are of theoretical and practical interest. The attention is focused on the sensors based on the electropolymerized natural phenolic antioxidants and their analytical application. The typical electropolymerization reaction schemes are discussed. Phenol electropolymerization leads to insulating coverage formation. Therefore, a combination of electropolymerized natural phenolic antioxidants and carbon nanomaterials as modifiers is of special interest. Carbon nanomaterials provide conductivity and a high working surface area of the electrode, while the polymeric film properties affect the selectivity and sensitivity of the sensor response for the target analyte or the group of structurally related compounds. The possibility of guided changes in the electrochemical response for the improvement of target compounds' analytical characteristics has appeared. The analytical capabilities of sensors based on electropolymerized natural phenolic antioxidants and their future development in this field are discussed.

An enzyme-free electrochemiluminescence insulin probe based on the regular attachment of ZnO nanoparticles on a 3-D nickel foam and H2O2 as an efficient co-reactant

In this study, a highly sensitive, fast, and enzyme-free electrochemiluminescence (ECL) probe based on the decoration of zinc oxide nanoparticles on nickel foam is proposed for insulin determination. A silica film was employed as a size adjusting agent for the modification of the nickel foam surface with ZnO nanoparticles (ZnO NPs). The ECL of the ZnO NP/Ni foam was investigated in a natural medium in the presence of hydrogen peroxide (H₂O₂) as an efficient co-reactant. With increasing insulin concentration, a remarkable improvement in ECL signal was observed, which proved the enhancing effect of insulin on the ECL emission. The characterization of the ZnO-NP/Ni-foam electrode was performed via electrochemical impedance spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurement, X-ray diffraction, field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray analysis techniques. The fabricated electrode was applied for the trace analysis of insulin using the ultrasensitive ECL method in a phosphate buffer solution. Under the optimal conditions, the results showed excellent performance during insulin determination with a wide linear range of 3.57 × 10^-15 M to 2.94 × 10^-9 M, a low detection limit of 1.00 × 10^-16 M, and a relative standard deviation of 1.03%. The proposed ECL sensor with excellent reproducibility, long-term stability, and high selectivity was used for insulin determination in real serum samples with acceptable outcomes.

Molecularly Imprinted Electrochemical Sensors: Analytical and Pharmaceutical Applications Based on Ortho-Phenylenediamine Polymerization

Background:

The molecular imprinting technique has been applied in many fields including separation, artificial antibody mimics, catalysis, sensing studies, and drug delivery. The reasons for the popularity of this technique among the researchers are high selectivity due to the cavities that are formed on the polymer surface for the specific analyte, high robustness, high durability under extreme conditions and low cost. When these advantages are combined with the advantages of electrochemical methods such as rapid response time, ease of use, cheapness and miniaturizability, Molecularly Imprinted Polymer (MIP) based electrochemical sensors turn out to be a widely-preferred sensing tool.

Objective:

This article provides the reader with information on MIP-based electrochemical sensors and reviews the applications of the MIP sensors prepared by electropolymerization of orthophenylenediamine, a monomer whose mechanical and chemical stability is very high.

Results and Conclusion:

The literature survey summarized in this review shows that cyclic voltammetry is the most widely preferred electrochemical technique for electropolymerization of o-PD. The media chosen is generally acetate or phosphate buffers with different pH values. Although there are numerous solvents used for template removal, generally methanol and NaOH have been chosen.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given.