Analytical & Bioanalytical Electrochemistry
Volume:11 Issue: 5, May 2019

In this research, the TiO2 film layered titanium foil (Ti/TiO2) electrode was performed for photo-assisted electrocatalytic determination of methanol in aqueous solution. TiO2 film was fabricated on the surface of titanium foil using anodizing this foil. The photoelectrochemical activity of methanol on the surface of the Ti/TiO2 electrode was investigated by cyclic voltammetry and hydrodynamic photoamperometry techniques. Also, hydrodynamic photoamperometry method was employed for methanol determination and for obtaining the best response. Also, pH and bias voltage were optimized based on the photocurrent differences value in the absence and presence of methanol. It was showed that the electrode photocurrent was linearly related to the methanol concentration in the range of 0.070-0.46 mM. The limit of detection was led to be 7.5 μM (3σ).

ZnO-CNTs and 1-butyl-3-methylimidazolium bromide (BMIB) ionic liquid were used as amplifiers for modification of carbon paste electrode (CPE) as simple and powerful electrochemical tool for analysis of tert-butylhydroquinone (TBHQ). The pH response on electro-oxidation signal of TBHQ was investigated as effective factor on voltammetric investigation. Under the optimized conditions, a linear dynamic rage 0.09–750 μmol L-1 was detected for determination of TBHQ at surface of CPE/BMIB/ZnO-CNTs. The CPE/BMIB/ZnO-CNTs was successfully used as electro-chemical food sensor for determination of TBHQ in food samples.

Sixteen electrochemical electrodes were prepared by modifying the electro-polymerized 3-methylthiophene to the below and above of the single-walled carbon nanotubes (SWCNTs) dispersion that dripped onto glassy carbon electrode. Determination of benserazide (BS) and levodopa (LD) in the presence of ascorbic acid (AA) was performed by differential pulse voltammetry (DPV) technique to find out which of these electrodes gave the best and fastest simultaneous response. The highest resolution and current densities were achieved with the electrode that 20 μL 1.0% SWCNT was dribbled onto the bare electrode. The morphology and structure of modified electrode were characterized by scanning electron microscopy. Under optimum conditions AA, BS and LD gave sensitive oxidation peaks at nearly 90, 210 and 320 mV, respectively. The oxidation currents increased linearly with concentration of BS (50-100 μM) and LD (5.0–9.5 μM) in phosphate buffer solution (pH 7.0). The detection limits obtained by DPV were 3.0 μM for BS and 1.1 μM for LD. Additionally, the proposed modified sensor was applied successfully to biological fluids and tablet samples. The results proved that the modified sensor showed excellent selectivity, repeatability and reproducibility with high stability and accuracy.

It is known, that conductivity of liquid media as well as biological objects directly related to the mobility of ions, which in turn depends on electric field strength. This article describes general principles and applications of method and hand-made conductometry device for measurement conductivity of a single biological cells and liquid media in pulsed electric field with rising strength. The device allows to determine the conductivity in the range 0.1-105 μS/cm (with an error about 3%) in the field strengths 0-10 kV/cm, pulse duration 50 μs, repetition period 5-10 s. Conductometric measurements were carried out on mouse and cow oocytes in 0.3 M solution of sucrose and some 0.3M aqueous solutions: xylitol, sorbitol, mannitol, glucose, sucrose, conventional distillate and deionized apyrogenic water. It was found that with rising in the field strength, the conductivity of cells first increases gradually and almost linearly in the range 0.2-1.3 kV/cm, and then sharper and finally exponentially, with strength more 2.8 kV/cm and 3.3 kV/cm for mouse and cow oocytes respectively, i.e., electric breakdown of the cell membrane occurs. The conductivity of liquid media is almost independent of the field strength, but small variations in some media have shown the presence of conductive impurities in them, which are absent in the solvent. Thus, the cell conductivity changes in rising field strength can detect and investigate all stages of membrane electroporation (reversible and irreversible electric breakdown) and the method can serve for estimating the purity of the initial reagents as well as quality control of other liquid media.

In this study, several heavy metal ions (Zn2+, Pb2+ and Cd2+) were extracted and online determined in water samples by ultrasound-assisted hollow fiber liquid phase micro-extraction (HF-LPME) coupled with stripping fast Fourier transform continuous cyclic voltammetry (SFFTCCV) as a novel electroanalytical technique. Initially, the heavy metal ions were extracted through a polypropylene membrane soaked in xylene and bis(2-ethylhexyl)phosphoric acid (DEHPA), into an acceptor solution located in the lumen of a hallo fiber (HF). The analytes were then determined through an electrochemical approach using a micro carbon paste electrode (micro-CPE) as a working electrode placed into the upper end of the HF. The optimum conditions for the proposed method were reached at scan rate of 6 V s−1, stripping potential: 200 mV, stripping time: 5 s, the sample solution pH: 5, the acceptor solution pH: 4, extraction time under the ultrasound irradiation: 60 min, membrane composition: 0.5 M DEHPA in xylene. Limit of detection (LOD) and limit of quantification (LOQ) were determined to be in the range of 0.1-1 and 1-5 ng.mL-1. Furthermore, the recovery percentages of 87%, 62% and 41% were obtained for Zn2+, Pb2+ and Cd2+ ions, respectively. Based on the results, the method presented adequate potential to be used for the simultaneous determination of the stated analytes in the sea, river and well water samples, under optimal conditions.

In this study, superparamagnetic iron oxide nanoparticles (SPIONs) are simply fabricated through a one-step electrodeposition method, and their in situ surface capping with dextran layer and crystal structure doping with zinc cations are simultaneously performed during their electrochemical synthesis. A simple conditions of room temperature, two-electrode electroplating, direct current synthesis and pH=6.7 were applied in the electrodeposition process. The fabricated SPIONs are characterized through Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating sample manometer (VSM), thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. These analyses results indicated that the prepared SPIONs have particles with 15nm size. The magnetic characters i.e. saturation magnetization (Ms), remanence (Mr) and coercivity (Hci) values of the fabricated SPIONs were measured to be 51.75 emu g–1, 0.16 emu g–1 and 3.35 Oe, respectively. It was found that the dextran surface capped-, zinc doped- SPIONs are proper candidates for biomedical investigations.

In this paper, EDTA-surface capped and cobalt-cations doped superparamagnetic iron oxide nanoparticles (EDTA/Co-SPIONs) are reported for the first time as a novel surface coated magnetic NPs. An easy and cheap electrochemical strategy is also developed for large-scale fabrication of EDTA/Co-SPIONs. For this aim, a simple cathodic base electrogeneration procedure was established where magnetite nanoparticles formation their surface capping with EDTA and crystal structure doping by Co cations were simultaneously achieved onto the cathode surface. The obtained EDTA/Co-SPIONs powder was analyzed through the structural, elemental and morphological analyses of FT-IR, EDAX, XRD, FE-SEM and DSC-TGA, and their magnetite (i.e. Fe3O4) crystal phase was verified by the XRD results, their 10 nm particle size was observed via FE-SEM microscopy, their structure doped with 10.69%wt cobalt cations was confirmed though EDAX data, and their surface coat with 10%wt. EDAT was cleared from the thermogravimetric data. VSM measurements proved the superparamagnetic behavior of the EDTA-capped EDTA/Co-IONs powder at the applied fields, where they presented proper saturation magnetization (Ms=36.55 emu g–1), negligible remanence (Mr=0.86 emu g–1) and low coercivity (Hci=9.74Oe). In final, it was concluded that the EDTA-capped Co2+ cations doped SPIONs with fine particles exhibit proper magnetic performances for biomedical uses.

An electrochemical potentiometric sensor was introduced for Fluoxetine (FLX) analysis in pharmaceutical formulations using conducting polymer coated on a solid-state contact. FLX is one of the antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. For this purpose, pyrrole was electrochemically polymerized on the surface of a solid contact made of graphite to form a thin layer of poly(pyrrole) (PPy). After this step, a thin layer of another polymeric composite composed of poly(vinyl chloride), dibutyl phthalate and ion-pair compound of FLX and phenyl borate was covered on the treated surface. The modified graphite rod was finally used as a working electrode in a potentiometric cell assembly. Linear concentration range of 1.0×10−6 to 1.0×10−3 mol L-1, lower detection limit of 6.3×10−7 mol L-1, 8s response time, and two months lifetime were the characterizations of the proposed sensor. Finally, FLX content of some pharmaceutical samples were analyzed by the prepared sensor accurately and precisely.

In this paper, we report well-dispersed superparamagnetic magnetite nanoparticles (SPMNs) surface-capped with polyvinylpyrrolidone (PVP) and structure-doped by Cu(II) ions. The SMNPs powder was obtained though galvanostatic two-electrode cathodic electrochemical synthesis. The prepared SPMNs samples were characterized via the structural and magnetical techniques of FE-SEM, EDS, TEM, XRD, FT-IR, and VSM. The magnetic data measured though VSM technique revealed superparamagnetic nature for the PVP-capped Cu-IONs sample, where relative high saturation magnetization, low remanence and negligible coercivity (i.e. Ms=45.01 emu/g, Mr=0.49 emu/g and Ce=7.3 Oe) were obtained for this sample. In the FT-IR data, all adsorption bands related the PVP polymer i.e. carbon-hydrogen, carbon-oxygen and carbon-nitrogen were detected and proved the surface-capped feature of the deposited iron oxide particles. It was also found that the fabricated magnetic powder had pure magnetite crystal structure doped by about 7.5%wt. copper cations and fine particle size of 5nm. Based on these results, the designed electrochemical procedure was introduced as an efficient and low cost synthetic way for fabricating the surface-capped metal cations doped magnetite ultra-fine particles.

Spherical-like cobalt aluminate nanoparticles were successfully synthesized by sol-gel method by new capping agent. The X-ray diffraction spectrum confirms the pure phase cobalt aluminate nanoparticles. The presence of stretching and bending vibrations of Co-O and Al-O confirmed by FT-IR analysis in the cobalt aluminate nanoparticles. The mean size of cobalt aluminate nanoparticles were examined by TEM techniques between 20 to 40 nm. The synthesized nanoparticle was used for determination of acyclovir. In the electrochemical section, the effects of pH, scan rate and Acyclovir concentration were studied. The peak current was linear with the acyclovir concentration in the range of 1μM to 30 μM and the detection limit was found to be 0.4μM.