Analytical & Bioanalytical Electrochemistry
Volume:14 Issue: 2, Feb 2022

Pb(II) is an important pollutant, known for seriously affecting humans and animals. The contemporary industrial activities and their emissions of various pollutants, lead ion included, have exacerbated such effects and have hence raised concern and attention on the implications on peoples’ health. Subsequently the quick, selective and accurate detection of lead ions in different environmental samples is receiving marked attention. Among the various tools and techniques developed and used for such purposes, electrochemical sensors constitute a prominent class. Yet in many cases, developing effective sensors, calls for developing selective ion receptors, and hence myriads of research projects have aimed at developing efficient selectophores for species like Pb(II) ions. The different ionophores developed have had their own pros and cons, and therefor different techniques have been used for designing more efficient alternative materials. An important approach in this regard, has been the application of ion imprinting technology for developing highly selective materials for use in ion-selective sensors. This review, tends to provide an outlook on the applications of ion imprinted polymers in developing Pb(II)-selective sensors, based on a review of the publications cited in Scopus database, on the development of Pb(II) sensors.

Lithium-ion batteries (LIB) have attracted enormous attention in the past decades due to their outstanding features, such as high energy density, long cycle life, low self-discharging capacity. Although Lithium-ion batteries have been an energy storage system for commercial electronics, issues regarding its safety raised doubt about its usage for energy storage. This paper presents a bilayer Li-ion battery separator produced by the wet method for its Polyethylene (PE) base layer, which has been reinforced by a nonwoven polyethylene terephthalate layer by electrospinning. This separator has appropriate porous morphology, 41% porosity, BET specific surface area of 39.3 m2/gr, an average pore diameter of 22 nm, electrolyte uptake of 216%, a tensile strength of 100 MPa, the ionic conductivity of 0.451 mS/cm, Excellent electrochemical stability up to 4.6 volts, acceptable cyclic performance and charge and discharge capacity which provides the expected characteristics of a suitable separator and, above all, due to the presence of a layer PET provides a shutdown safety window of about 100 degrees Celsius by improving its dimensional stability under high temperatures.

A composite of multi-walled Carbon nanotube (MWCN) and polyvinyl chloride (PVC) along with a synthesized neutral carrier 4,7-diaza-2,3,8,9-dibenzo-15-crown-5 (I) has been tried for its selective binding behavior for Ca(II) ions. Compound (I) works as an ionophore, exhibiting high selectivity for calcium ions, when taken with poly(vinyl chloride), sodium tetraphenylborate (NaTPB), MWCNT and  tris(2-ethylhexyl) phosphate (TEP) in the ratio 10:100:3:3:50 (w/w). This composition was used to fabricate a solid contact calcium(II)- selective potentiometric sensor. The developed all solid-state sensor worked well in the concentration range of 1.6×10-7-1.0×10-1 M, with a near Nernstian slope of 28.8+1.0 mV/decade of activity. The response time of this sensor was approximately 10 s. It exhibited a detection limit of 9.1×10-8 M. It worked satisfactorily in the pH range 3.5-7.0. The lifetime of the developed sensor was observed as six weeks and it exhibited good selectivity towards calcium ions over other cations.  It was successfully used as an indicator electrode in the potentiometric titration of Ca(II) with EDTA. It produced comparable results for the determination of the activity of calcium ions in real samples.

A unique potentiometric ion-selective PVC membrane sensor was developed based on tramadol-(tetraphenylborate) as the sensing element, tetraphenylborate as an additive, and dibutyl phthalate (DBP) as the plasticizer solvent for the measurement of Tramadol in pharmaceutical preparations. Different parameters such as the electrode conditioning time, the effect of electrode materials, and the impact of pH solution on the electrode performance were evaluated. The electrode showed a Nernstian slope of 59.5±0.4 mV/decade for tramadol ions. The potentiometric sensor reported here has been optimized to provide excellent analytical performance with a linear in the concentration spectrum 1.0×10-7-1.0×10-1 mol L-1 and a limit of quantification of 7.0×10-8 mol L-1. The sensor has a reaction time of 5 seconds and can be utilized in the pH range of 2.0 to 7.0. With a mean relative standard deviation of less than 2%, the approach is effective and reliable. The current electrode would be used to detect tramadol hydrochloride in biological samples with excellent results.

In the presented study, for the first time, simultaneous electrochemical measurements of ascorbic acid (AA), melatonin (Mel), and tryptophan (Trp) were discussed. The CuO-CeO2-rGO-MWCNTs nanocomposite was prepared, then applied for amendment of glassy carbon electrode (GCE) surface to the measurement of target analytes using differential pulse voltammetry (DPV) technique. Electrical impedance spectroscopy (EIS) techniques displayed that CuO-CeO2-rGO-MWCNTs/GCE has the lowest electron transfer resistance (Rct) in comparison to GCE and was suitable for electrochemical applications. The synthesized compounds were analyzed by powerful methods including Scanning Electron Microscopy (SEM) and, X-ray Diffraction (XRD). At the CuO-CeO2-rGO-MWCNTs/GCE, three oxidation peaks appeared at 0.309, 0.631, and 0.855 V for AA, Mel, and Trp and the peaks separation of ΔEp (AA and Mel)=322 mV, and ΔEp (Mel and Trp)=224 mV in the electrochemical potential window of 0.0-1.1 V. In optimum DPV condition and pH=5.0, a dynamic range of AA (0.01-28 µM), Mel (0.01-12.6 µM) and Trp (0.01-13.5 µM) with the detection limit of 9, 8 and 7.3 nM for AA, Mel, and Trp, respectively, were acquired. The provided modified electrode was successfully used to monitor the analytes in human biological fluids.

This paper investigates the influence of grain size reduction, from 120 to 5 µm, on the electrochemical response of Fe-18.5% Cr ferritic stainless steel in 0.01 M NaOH alkaline solution. To analyze the electrochemical characteristics of the material, the potentiodynamic polarization, open circuit potential measurement, cyclic voltammetry, electrochemical impedance spectroscopy, and Mott-Schottky analysis were carried out. Open circuit potential analysis demonstrated that the passive layer developed on a coarse-grained sample is more stable than a fine-grained one. Based on electrochemical impedance spectroscopy measurements, it was concluded that grain refinement reduces the thickness of the passive protective layer and degrades the corrosion resistance of material. Polarization measurements showed that refinement of grain structure reduces the corrosion resistance of the investigated ferritic stainless steel exposed to NaOH solution. The Mott-Schottky analysis demonstrated that the protected layer formed on the surface of the fine-grained sample has donor and acceptor densities (2.43×1021, and 0.4×1021 cm-3, respectively) higher than that formed on the surface of the coarse-grained counterpart (2.29×1021, and 0.36×1021 cm-3, respectively).

In this study, an electrochemical sensitive sensor based on thioglycolic acid decorated cadmium selenide (CdSe) doped graphene oxide modified graphite electrode was successfully developed for the simultaneous determination of morphine and methadone. The electrode process was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV).Nanocomposite structure was characterized by FTIR and EDX and XRD. Taguchi’s experimental design method was applied to determine the optimum operating conditions such as pH, bandwidth, scan rate and buffer concentration. And according to the results, pH and buffer concentration were determined as the most effective parameters on the performance of the modified electrode. Under optimized conditions, the calibration curve for methadone presents two linear ranges of current versus analytes concentration in the range of 0.1 to 20 μM and 20 to 323 μM, and 0.05 to 350 μM for morphine, with the detection limits of 0.03μM. For methadone 0.04μM for morphine (3sb / B).The quantification limits, and precision were found to be acceptable. Finally, the developed method was successfully applied for target analytes determination in blood sera taken from different volunteers.

Nitro-tyrosine is produced via tyrosine nitration by reactive nitrogen species such as peroxynitrite and NO2. Nitrotyrosine presence in the body is an indicator for cell damage and inflammation issue. Hence, the monitoring of this biomarker is an important task. Since nitro-tyrosine is produced from tyrosine, these two molecules are present concurrently in the real samples. In this work electrooxidation of nitro-tyrosine and tyrosine was checked on glassy carbon and carbon paste electrodes (CPE) utilizing cyclic voltammetry and differential pulse voltammetry methods. It was found that nitro-tyrosine creates an oxidation signal at the GC electrode, whereas, no significant oxidation peak was found for tyrosine in the GC electrode. In the case of CPE, However, both nitro-tyrosine and tyrosine showed oxidation peaks which were separated by about 0.1 V/Ag/AgCl. Applying DPV led to better resolution of oxidation peaks of tyrosine and nitro-tyrosine. Moreover, the separation of the peaks was improved when DPV was replaced with CV.  Solution pH and the binder content of the carbon paste electrode were optimized in order to achieve maximum signal for both compounds. The calibration curves were established utilizing CPE and DPV techniques.

Based on the results of the complexation reaction between 1-acenaphthoquinone 1-thiosemicarbazone (L) and some metal ions in methanol, it was found that the ligand forms a stable 1:1 complex with Ni2+ ions among the range of ions tested. Accordingly, this hydrazone derivative was chosen and evaluated as an ionophore for use in the construction of polymeric membrane sensors with selectivity towards Ni ions. The resulting membrane electrode, under optimal conditions, had a Nernstian slope of 29.5±0.2 mV/decade over a wide concentration window of 1.0×10-6-1.0×10-1 M, and its limit of detection was as low as 5.0×10-7 M.  The electrode had very good selectivity coefficients for other commonly occurring cations in its response range. The proposed potentiometric sensors possess response times of 10 sec, good reversibility, and are applicable for over 12 weeks after their first use. The response of the membrane sensor was pH-independent in the pH range of 5.0–8.0, and it was used in the analysis of nickel ions concertation in real water samples with satisfactory results. The electrode was also used in the potentiometric titration of nickel ions using a standard ethylenediaminetetraacetic acid (EDTA) solution at pH=6.0.