Analytical and Bioanalytical Chemistry Research
Volume:7 Issue: 3, Summer 2020

Bioelectrocatalysis is a phenomenon concerned with biological catalysts, which accelerate the electrochemical reactions. Bioelectrocatalysis has been widely explored by the research community in various directions. Enzymes can catalyze different chemical reactions in living organisms by enzymes as the most important biological catalysts. These enzymatic biocatalysts are commercially available and commonly called enzyme electrodes. Electron transfer between the active center of the enzyme and the electrode can be performed either by direct electron transfer (DET) or by means of mediators (i.e. mediated electron transfer (MET)), which are discussed in details in the presented review. Therefore, different strategies have been used to increase the efficiency and stability of bioelectrocatalysis. In this review, different strategies of the bioelectrode designs have been discussed and the application of the common bioelectrodes used in the biosensors have been presented in the various fields. Moreover, a summary of the research status in the applications of bioelectrocatalysis in biosensors and biofuel cells was provided.

Migration of chemicals from plastic containers into drinks and liquids containing them, is supposed to be a hazardous phenomenon and results in many health problems. Sample preparation is of great importance due to trace amounts analysis of these compounds. In this research, dispersive liquid–liquid microextraction is applied for the extraction and preconcentration of the migrated compounds prior to their detection and determination by gas chromatography equipped with mass spectrometry or flame ionization detector. The method is on the basis of forming droplets of a water–immiscible organic solvent (extractant) into an aqueous phase by means of a disperser solvent. As a result, there would be a large contact area between the extractant and aqueous phase containing the analytes which boosts mass transfer. After centrifuging, the extractant is sedimented at the bottom of the aqueous phase and an aliquot of it is removed and injected into the separation system. Various experimental conditions which influence the extraction efficiency were optimized. Under the optimum conditions, the extraction recoveries were ranged from 52–63%. The relative standard deviations were ≤ 7.2% for intra– (n = 6) and inter–day (n = 4) precisions at a concentration of 20 µg L–1 of each analyte. The limits of detection were in the range of 0.18–0.38 µg L–1. Eventually the applicability of the proposed method for appraising the compounds migrated from the plastic containers was evaluated by analyzing the target compounds in different drinks and liquids stored in the plastic bottles.

In this study, an easy, fast, sensitive and accurate technique has been described for extraction and quantitative analysis of fluoxetine and propafenone using off-line coupling of ionic liquid–based dispersive liquid–liquid micro-extraction with high performance liquid chromatography. The effective extraction variables including: the ionic liquid volume, the type and volume of dispersive solvent, the pH, the extraction and centrifugation time, and the volume of diluent solvent have been investigated and optimized. The optimum chromatographic conditions were also obtained for the drugs determination. Under optimum conditions, the analytical curves were linear (r > 0.999) within a wide concentration range (0.01–2.00 μg mL-1). Relative standard deviations (precision) and detection limits for both drugs have been smaller than 5% and 0.005 μg mL-1, respectively. The proposed method has been used successfully to detect and determine fluoxetine and propafenone in the capsule formulation and the spiked plasma samples; respectively, with the quantitative recovery results (94–97%).

The presented study describes the solvent extraction process of Zn(II) and Pb(II) from aqueous solutions by a cation exchanger extractant named bis(2-ethylhexyl)phosphoric acid (DEHPA). The results confirm that both of the extraction efficiency and extraction selectivity depend on the employed organic diluent. The applied extractant was selective towards zinc ions; this selectivity did not depend on the employed organic diluent. Keep in mind the possible interaction of the studied metal ions with the polyether compounds (PEGs) dissolved in the aqueous phase, the role of the presence of two PEGs with molecular masses 200 (PEG200) and 2000 (PEG2000) on the selectivity characteristics of the proposed extraction system was appraised. The evaluated PEGs play the role of masking agents by complexing the lead ions in the aqueous phase, while the zinc ions did not interact with them. These interactions result in the transposition of the extraction curves of lead as a function of pH, towards higher pH regions, whereas the extraction curves of zinc remained almost unchanged. By replacing the organic diluent (CCl4), by another one capable to dissolve the complexed lead ions with PEG200 (e.g. chloroform), a synergistic extraction was observed. This latter observation clearly showed the decisive impact of the employed solvent on the effect of the investigated PEGs to act as a masking or synergistic agent in the studied solvent extraction system.

In this work, electrochemical behavior of Caffeic Acid (CA) in absence and presence of aromatic amines such as 4-amino-1,3-Dimethyluracil (4A-DMU), p-toluidine (p-TI), and Sulfacetamide (SA) have been performed by cyclic voltammetry technique in water (sodium acetate, c = 0.15 M)/ethanol (80:20, v/v) mixture. In this way, the effect of different parameters such as concentration and scan rate indicated that the oxidation mechanism of caffeic acid (CA) in the presence of aromatic amines can be EC and ECE. At the working electrode surface, Caffeic Acid (CA) oxidized to correponding o-benzoquinone (CAOX) with two electrons and two protons process. In the following, the Michael-type addition reaction has occurred between o-benzoquinone and aromatic amines. In the second cycle, a new oxidation peak appears in negative potentials than Caffeic Acid (CA) oxidation peak because of the electron-donating properties of amines. Cyclic voltammetry technique can recognize chemical and electrochemical processes in solution and electrode surface, respectively.

In the present study, hollow fiber liquid-phase microextraction (HF-LPME) method was used to preconcentrate trace amount of phenol prior to its spectrophotometric determination. Phenol reacted with 4-aminoantipyrine (4-AAP) reagent in presence of potassium hexacyanoferrate (III) and then was extracted into the octanol extractant inserted into the lumen and pores of hollow fibers. Some factors such as concentrations of 4-aminoantipyrine, potassium hexacyanoferrate (III) and ammonium chloride, the rate of stirring, and extraction time were optimized using response surface method based on the central composite design (CCD). Under the optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.5 and 5 μg L-1, respectively. Also, the relative standard deviation (RSD %) and enrichment factor (EF) were obtained as 4.9 % and 174, respectively. In addition, the suggested method was implemented to measure of phenol concentration in some real samples, including wastewater of wood and textile factories, as well as the extracts of mint, and green tea. The accuracy was investigated by the recovery of phenol from real samples in the range of 82.3 – 112%. The results showed that the proposed method is simple, rapid, eco-friendly, and accurate for preconcentration and analysis of phenol.

In this work, we introduced a sensitive electrochemical sensor in order to accurately detect metanil yellow (MY). Multi-walled carbon nanotube-chitosan (MWCNTs-Chit) nanocomposite was applied to fabricate the sensor on the glassy carbon electrode. The scanning electron microscopy (SEM) was used to investigate the physical morphology of the modified electrode surface. The rate of the electron transfers between MY and electrode can be quickened by the attendance of MWCNTs-Chit nanocomposite due the high surface area, good conductivity as well as excellent catalytic property. Sensitive quantitative detection of the MY was carried out by the monitoring increase of differential pulse voltammetric (DPV) responses of the sensor. The prepared MWCNTs-Chit/GC electrode illustrated a linear response to MY concentration in the range of 1.0 µM to 300.0 µM with a sensitivity and a limit of detection (S/N=3) of 20.0 nAµM-1 and 0.3 µM, respectively. Accordingly, in order to determine MY in real samples with satisfactory results, we applied the proposed sensor.

So far, several methods, including DPPH, FRAP, and TEAC have been suggested for considering the antioxidant capacity, each with disadvantages, including the need for expensive tools, low sensitivity, and complexity. One of the most accurate methods is the TEAC method, due to the use of protein enzymes, which possess disadvantages such as activity in the limited temperature range, and instability against hydrolysates and hard storage conditions. Therefore, antioxidant capacity measurements using the peroxidase-like trivalent deoxyribozyme used. The results showed that trivalent deoxyribozyme had more catalytic activity than monomeric deoxyribozyme. Also, kinetic parameters such as kcat, Km, and Vmax were calculated in the presence of H2O2, which equal to 4.32 (min-1), 8.744 (µM), and 0.864 (µM/min), respectively. The results of calculating RAC for the extracts of Dacrocephalum and Black cardamom plants were estimated to be 28.59 and 11.79, respectively. Also, the limit of detection (LOD) was found for Trolox, Ferulic acid, and Caffeic acid obtained about o.27, 0.14 and 0.28 (µM) by UV-vis spectroscopy. Also, LOD is 5.0, 2.0, and 2.5 (µM) by the naked eye for the mentioned antioxidants, respectively. These results indicated that antioxidant capacity measurements using the peroxidase-like trivalent deoxyribozyme have advantages such as cheapness, simplicity, observation with naked eyes, stability, and high sensitivity to the other methods.

This paper describes the kinetics of the electropolymerization of 4-amino-3-methyl-1,2,4-triazole-5-thiol (MTSNH) on a brass substrate in alkaline solution containing methanol. Our laboratory has developed a new synthesis strategy for MTSNH. This compound was purified and characterized by 1HNMR and 13CNMR spectroscopies. The electrochemical study was investigated using cyclic polarization, chronoamperometry, electrochemical impedance techniques and scanning electronic microscopy. The polymeric film was achieved by successive cyclic voltammetry sweep between 0 and 2.2 V at the scan rate of 10mV/s. The effect of the scan rate for 10-3 M of MTSNH in a basic solution of potassium hydroxide 0.1 M containing methanol shows that the increase of the scan rate is accompanied by the increase of the intensity of the first oxidation peak, which indicates the acceleration of the studied process. We have also shown that the monomer oxidation reaction is essentially irreversible and controlled by a diffusion process. The protective effect of the film formed on brass has been studied in a 3% NaCl. The results showed important inhibition efficiency, about 83% for 1 h of testing time.

Erythromycin is one of the typical macrolides, which is isolated by the Saccharopolyspora ‎erythraea. It has been listed in WHO essential medicine for improvement of the efficiency of ‎health system. In this study, magnetic iron nanoparticles were coated with cetyl as a non-polar ‎functional group and characterized by various techniques such as Infrared Spectroscopy, ‎thermal gravimetric analysis‎, scanning electron microscopy and vibrating sample ‎magnetometer. The as-prepared nanoparticles were used to extract erythromycin from the milk ‎samples. Separation was performed on a pentaflurophenyl column (150*2mm,3μm) using a ‎mobile phase consisting 70% acetonitrile and 30% ammonium acetate (10mM, pH3.5) with a ‎high performance liquid chromatography system coupled with tandem mass spectrometry‏.‏‎ The ‎separation was fast and completed in less than 5 minutes, under the optimized condition. Stable ‎isotope of erythromycin was used as internal standard in the sample preparation and calibration ‎curve. It was found that relative recovery of the method was 92.6%. The proposed method was ‎convenient and quick preparation method was achieved using external magnetic field without ‎centrifugation and filtration‏.‏‎ The detection limit and coefficient of determination were 2.4 ‎μg/L and R2 = 0.9983, respectively. The intra- and inter-day precisions of the proposed method ‎in different levels of spiked sample were in the range of 5.6-8.5% and 8.4-12.5%, respectively.‎