Analytical Performance of Clay Paste Electrode and Graphene Paste Electrode-Comparative Study

The analytical performance of the clay paste electrode and graphene paste electrode was compared using square wave voltammetry (SWV) and cyclic voltammetry (CV). The comparison was made on the basis of a paracetamol (PA) determination on both working electrodes. The influence of pH and SWV parameters was investigated. The linear concentration ranges were found to be 6.0 × 10⁻⁷–3.0 × 10⁻⁵ and 2.0 × 10⁻⁶–8.0 × 10⁻⁵ mol L⁻¹ for clay paste electrode (ClPE) and graphene paste electrode (GrPE), respectively. The detection and quantification limits were calculated as 1.4 × 10⁻⁷ and 4.7 ×10⁻⁷ mol L⁻¹ for ClPE and 3.7 × 10⁻⁷ and 1.2 × 10⁻⁶ mol L⁻¹ for GrPE, respectively. Developed methods were successfully applied to pharmaceutical formulations analyses. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize ClPE and GrPE surfaces. Clay composition was examined with wavelength dispersive X-ray (WDXRF).     

Voltammetric Determination of an Anti-rheumatoid Drug Acemetacin on Graphite Flake Paste Electrode and Glassy Carbon Electrode

In this study, a simple and sensitive square wave voltammetric procedure has been developed for the determination of acemetacin (ACM) at graphite flake paste electrode (GFPE) and glassy carbon electrode (GCE). Under optimized conditions, the dependence of ACM peak current on its concentration showed wide linear range: 0.03–1.0 μmol L⁻¹ and 0.7–15.0 μmol L⁻¹ at GFPE and GCE, respectively. The developed method was successfully applied for the determination of ACM in pharmaceuticals and spiked urine with satisfying recoveries. The electrochemical oxidation of ACM is an irreversible process controlled by mixed nature of the mass transfer process.     

A Comparison of Edge-plane and Basal-plane Pyrolytic Graphite Electrodes towards Sensitive Determination of the Fungicide Mandipropamid

A sensitive square-wave voltammetry (SWV) method based on basal-plane pyrolytic graphite electrode (BPPGE) and edge-plane pyrolytic graphite electrode (EPPGE) was developed to determine the concentration of the pesticide mandipropamid (MAN) in spiked river water and grape juice samples. Under optimal experimental conditions, the SWV response of EPPGE and BPPGE was linear over the concentration ranges of 0.7 to 9.0 μmol L⁻¹ and 0.5 to 10.0 μmol L⁻¹, respectively. The method was successfully used to determine MAN in spiked samples with good recovery. Cyclic voltammetry (CV) was conducted to understand the mechanism underlying the electrode process of MAN.     

Measuring the Electrode Kinetics of Vitamin B2 at a Constant Time Window of a Square Wave Voltammetric Experiment

The electrode kinetics of vitamin B2 was measured at a constant scan rate of a square‐wave (SW) voltammetric experiment by recently introduced method based on alteration of the height (amplitude) of the SW potential pulses. The electrode reaction mechanism was analyzed in the light of the simplified model considering two‐electron one step surface electrode mechanism, as well as to more appropriate EE surface reaction pathway consisting of two successive one‐electron quasireversible reactions. Theoretical analysis indicated that the evolution of the voltammetric response under variation of the SW amplitude enables estimation of the rate determining step of the EE mechanism.     

Voltammetric behavior and quantitative determination of ambazone concentrations in urine and in a pharmaceutical formulation

The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about ?1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10^?9 to 1.0×10^?7 mol L^?1. The detection and quantification limits were found to be 3.0×10^?10 mol L^?1 and 1.0×10^?9 mol L^?1, respectively. The proposed method was successfully applied to ambazone determination in real samples.      

Electrochemical oxidation of methylthiomethyleneisoquinolinium chloride — the first water soluble alkylthiomethylene substituted ammonium salt

Electrochemical oxidation of methylthiomethyleneisoquinolinium chloride (MTMIQ), the first alkylthiomethyl substituted ammonium salt, which is fully miscible with water has been investigated by voltammetric (SWV) method using glassy carbon electrode. On the electrode, MTMIQ undergoes oxidation at the potential near Ep = 0.07V (vs. Ag/AgCl/3 M KCl). The influence of the pH of buffers, amplitude, frequency, step potential on the received signal was studied. The best results were obtained with a citrate buffer at a pH of 5. The oxidation peak current used for MTMIQ voltammetric determination was in the range of 2–8×10⁻⁵ mol L⁻¹, LOD = 3.7×10⁻⁶, LOQ = 1.2×10⁻⁵. The product of the oxidation was accumulated at the working electrode and was investigated by spectroscopic method. Mechanistic pathways of the oxidation have been proposed.      

Highly Sensitive Determination of Tenofovir in Pharmaceutical Formulations and Patients Urine—Comparative Electroanalytical Studies Using Different Sensing Methods

This paper discusses the electrochemical behavior of antiviral drug Tenofovir (TFV) and its possible applicability towards electroanalytical determination with diverse detection strategies using square-wave voltammetry. Namely, oxidation processes were investigated using glassy carbon electrode with graphene oxide surface modification (GO/GCE), while the reduction processes, related to the studied analyte, were analyzed at a renewable silver amalgam electrode (Hg(Ag)FE). Scanning electron microscopy imaging confirmed the successful deposition of GO at the electrode surface. Catalytic properties of graphene oxide were exposed while being compared with those of bare GCE. The resultant modification of GCE with GO enhanced the electroactive surface area by 50% in comparison to the bare one. At both electrodes, i.e., GO/GCE and Hg(Ag)FE, the TFV response was used to examine and optimize the influence of square-wave excitation parameters, i.e., square wave frequency, step potential and amplitude, and supporting electrolyte composition and its pH. Broad selectivity studies were performed with miscellaneous interfering agents influence, including ascorbic acid, selected saccharides and aminoacids, metal ions, non-opioid analgesic metamizole, non-steroidal anti-inflammatory drug omeprazole, and several drugs used along with TFV treatment. The linear concentration range for TFV determination at GO/GCE and Hg(Ag)FE was found to be 0.3–30.0 µmol L^–1 and 0.5–7.0 µmol L^–1, respectively. The lowest LOD was calculated for GO/GCE and was equal to 48.6 nmol L^–1. The developed procedure was used to detect TFV in pharmaceutical formulations and patient urine samples and has referenced utilization in HPLC studies.     

Voltammetric Determination of Proguanil in Malarone and Spiked Urine with a Renewable Silver Amalgam Film Electrode

Electrochemical properties of proguanil were investigated by a voltammetric method (SWV) using a renewable silver amalgam film electrode. The influence of buffer pH as well as potential amplitude, frequency, and step potential was studied. The repeatability, precision and recovery of the developed method were examined. The reduction peak current was used for proguanil voltammetric determination in the range 1×10^?7–6×10^?6 mol L^?1, LOD=2.9×10^?8 mol L^?1, LOQ=9.7×10^?8 mol L^?1. The standard addition method was used to determine proguanil in a commercial formulation (Malarone) and in spiked urine.     

Renewable Silver Amalgam Film Electrode for the Determination of Dinotefuran in Spiked Carrot Juice Samples Using SW Voltammetry

The electrochemical properties of dinotefuran (DNF) were studied by SW voltammetry over the pH range 2.0–8.0 using a silver amalgam film electrode Hg(Ag)FE. The mechanism of electroreduction was analyzed. The dependence of the peak current on pH, buffer concentration, the nature of the buffer, amplitude, frequency, step potential and scan rate were investigated. The repeatability, precision and recovery of the developed method were checked. The detection and quantification limits were found to be 2.01×10^?7 and 6.71×10^?7 mol L^?1, respectively. The standard addition method was used to determine DNF in spiked carrot juice.     

Determination of Blasticidin S in Spiked Rice Using SW Voltammetry with a Renewable Silver Amalgam Film Electrode

Blasticidin S (BS) was determined in spiked rice samples by square wave voltammetry (SWV) and square wave stripping voltammetry (SWSV) using a cyclic renewable silver amalgam film electrode (Hg(Ag)FE). It was found that the compound can act as an electrocatalyst. In Britton? Robinson buffer at pH 7.0 a signal connected with the hydrogen evolution reaction was detected at ?1.2 V versus Ag/AgCl. Validation of the method was carried out. The detection and quantification limits were found to be 2.13×10^?8 mol L^?1; 7.10×10^?8 mol L^?1 for SWV and 2.65×10^?9 mol L^?1; 8.85×10^?9 mol L^?1 for SWSV, respectively.