Graphene derivatives-based electrodes for the electrochemical determination of carbamate pesticides in food products: A review.

Graphene (GR) composites have great potential for the determination of carbamates pesticides (CPs) by electrochemical methods. Since the beginning of the 20th century, GR has shown remarkable promise as electrode material for various sensors. The contamination of food products with harmful CPs is a major problem as they do not always damage human health immediately, but can be harmful after prolonged exposure. A range of advantages can be gained from their electrochemical determination, such as high sensitivity, reasonably selectivity, rapid detection, low limit of detection, and easy electrode fabrication. Furthermore, these electrochemical techniques are robust, reproducible, user-friendly, and conform to both "green" and "white" analytical chemistry. This review is focused on results published in the last ten years in the field of electrochemical determination of CPs in food products using GR and its derivatives.

Electrochemical Sensors for the Detection of Reactive Oxygen Species in Biological Systems: A Critical Review.

Reactive oxygen species (ROS) involving superoxide anion, hydrogen peroxide and hydroxyl radical play important role in human health. ROS are known to be the markers of oxidative stress associated with different pathologies including neurodegenerative and cardiovascular diseases, as well as cancer. Accordingly, ROS level detection in biological systems is an essential problem for biomedical and analytical research. Electrochemical methods seem to have promising prospects in ROS determination due to their high sensitivity, rapidity, and simple equipment. This review demonstrates application of modern electrochemical sensors for ROS detection in biological objects (e.g., cell lines and body fluids) over a decade between 2011 and 2021. Particular attention is paid to sensors materials and various types of modifiers for ROS selective detection. Moreover, the sensors comparative characteristics, their main advantages, disadvantages and their possibilities and limitations are discussed.

Quantitative determination of new anti-inflammatory drug indomenthyl and its metabolite in rabbit plasma by HPLC-MS/MS.

Background: Indomenthyl is an innovative anti-inflammatory drug with a high analgesic activity. Indomenthyl releases indomethacin under the influence of neutrophil esterases in the inflammation focus. Methodology/results: This research is aimed at developing a highly sensitive method for the quantitative determination of indomenthyl and its active metabolite indomethacin in rabbit plasma by HPLC-MS/MS. Protein precipitation and extraction with acetonitrile were used for analyte isolation from plasma according to the QuEChERS principle. The target quantitative ion pairs m/z were respectively 496.4 → 358.0 for indomenthyl, 358.0 → 139.5 for indomethacin, and 340.1 → 202.1 for the IS. Conclusion: The calibration curve was linear over the range 0.1-1000 ng mL-1. The technique was applied to the pharmacokinetic study at a dose of 25 mg kg-1 to rabbits.

A Laser Reduced Graphene Oxide Grid Electrode for the Voltammetric Determination of Carbaryl.

Laser-reduced graphene oxide (LRGO) on a polyethylene terephthalate (PET) substrate was prepared in one step to obtain the LRGO grid electrode for sensitive carbaryl determination. The grid form results in a grid distribution of different electrochemically active zones affecting the electroactive substance diffusion towards the electrode surface and increasing the electrochemical sensitivity for carbaryl determination. Carbaryl is electrochemically irreversibly oxidized at the secondary amine moiety of the molecule with the loss of one proton and one electron in the pH range from 5 to 7 by linear scan voltammetry (LSV) on the LRGO grid electrode with a scan rate of 300 mV/s. Some interference of the juice matrix molecules does not significantly affect the LSV oxidation current of carbaryl on the LRGO grid electrode after adsorptive accumulation without applied potential. The LRGO grid electrode can be used for LSV determination of carbaryl in fruit juices in the concentration range from 0.25 to 128 mg/L with LOD of 0.1 mg/L. The fabrication of the LRGO grid electrode opens up possibilities for further inexpensive monitoring of carbaryl in other fruit juices and fruits.

A copper nanoparticle-based electrochemical immunosensor for carbaryl detection.

A hapten-protein conjugate with copper nanoparticles (Hap-Car-BSA@CuNPs) was first synthesized in the present work for the determination of carbaryl. The copper nanoparticles (CuNPs) of the conjugate were used as electrochemical labels in the direct solid-phase competitive determination of carbaryl residues in flour from different crops. The signal was read by linear sweep anodic stripping voltammetry (LSASV) of copper (through the electrochemical stripping of accumulated elemental copper) on a gold-graphite electrode (GGE). To form a recognition receptor layer of monoclonal antibodies against the carbaryl on the surface of the GGE, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 1-hydroxy-2,5-pyrrolidinedione (NHS) were used as the best covalent cross-linkers. The concentrations of the antibodies and the Hap-Car-BSA@CuNPs conjugate were optimized for carbaryl detection by the electrochemical immunosensor. The electrochemical immunosensor can be used for highly sensitive determination of carbaryl residues in flour samples in the concentration range 0.8-32.3 µg·kg-1, with a limit of detection 0.08 µg·kg-1. The present work paves the path for a novel method for monitoring carbaryl in other food products, drinks, and soil samples.

An electrochemical sensor for detecting selenium in biological fluids on an arenediazonium tosylate-modified metal electrode.

This article presents the results on using a new electrochemical sensor modified with arenediazonium salts (MGE-Cu-COOH) to determine selenium in biological fluids (blood serum). It was shown that the sensitivity of the determination of selenite ions using this modified electrode is higher compared to that of the unmodified one (MGE-Cu). The effect of the concentration of arenediazonium tosylates on various substituents was studied, and the conditions for the production of the electrochemical sensor were developed. The surface of the modified electrode was investigated using SEM. The increase in the effective surface area of the electrode was found to be due to the formation of a system of ultramicroelectrodes. In biological samples, the LOD and LOQ of selenium were established at the levels of 0.057 and 0.166 µg l-1, respectively. Finally, the correctness of the results on selenium determination in real samples by the "input-found" method, which correlates well with the known value, was verified.

Study of total antioxidant activity of human serum blood in the pathology of alcoholism.

The total antioxidant activity (TAA) of human serum blood of patients suffering from alcoholism was tested by cathode voltammetry with a model process of oxygen electroreduction. A known spectrophotometrical method was used for comparison. As results the total antioxidant activity of serum blood of patients with alcoholism was estimated by voltammetry during therapy in hospital. It was shown the TAA of serum blood of patients in pathology before and after treatment is lower than that one of healthy people. However, during the process of 10 days of alcoholism treatment the TAA coefficient increases. The relationship between the coefficient of total antioxidant activity of human serum blood and the stage of treatment was detected.

Study of OH radicals in human serum blood of healthy individuals and those with pathological schizophrenia.

The human body is constantly under attack from free radicals that occur as part of normal cell metabolism, and by exposure to environmental factors such as UV light, cigarette smoke, environmental pollutants and gamma radiation. The resulting "Reactive Oxygen Species" (ROS) circulate freely in the body with access to all organs and tissues, which can have serious repercussions throughout the body. The body possesses a number of mechanisms both to control the production of ROS and to cope with free radicals in order to limit or repair damage to tissues. Overproduction of ROS or insufficient defense mechanisms leads to a dangerous disbalance in the organism. Thereby several pathomechanisms implicated in over 100 human diseases, e.g., cardiovascular disease, cancer, diabetes mellitus, physiological disease, aging, etc., can be induced. Thus, a detailed investigation on the quantity of oxygen radicals, such as hydroxyl radicals (OH(•)) in human serum blood, and its possible correlation with antioxidant therapy effects, is highly topical. The subject of this study was the influence of schizophrenia on the amount of OH(•) in human serum blood. The radicals were detected by fluorimetry, using terephthalic acid as a chemical trap. For all experiments the serum blood of healthy people was used as a control group.