Application of a Graphene Oxide–Carbon Paste Electrode for the Determination of Lead in Rainbow Trout from Central Europe

In the presented study, the content of lead in rainbow trout (Oncorhynchus mykiss) samples was examined. Rainbow trout were purchased in Prague (Czech Republic), Lodz (Poland) and Bratislava (Slovakia) from local fish shops and supermarkets belonging to popular chain stores. First, method for quantitative lead determination was developed with very good results (R 2 at 0.9997 in the range of 1.0 × 10−7–7.0 × 10−5 mol L−1 with limit of detection (LOD) and limit of quantification (LOQ) 2.18 × 10−8 and 7.24 × 10−8 mol L−1, respectively). Then, after mineralization, fish samples were analyzed using square wave anodic stripping voltammetry (SWASV) with a graphene oxide–carbon paste electrode (GO–CPE). Lead signals recorded on GO–CPE electrode were 15 % higher than those obtained on bare CPE. The coefficient of variation (CV) was found to be below 5 %. The selectivity of the proposed method was evaluated by the addition of selected heavy metals (zinc, copper, mercury, cobalt, nickel, iron) as possible interferents. Results were confirmed with reference method.Financial support of the grant 506/1123 from the Ministry of Science and Higher Education is gratefully acknowledged

Electroanalysis of pindolol on a GCE modified with reduced graphene oxide

Publikacja w ramach programu Royal Society of Chemistry "Gold for Gold" 2014 finansowanego przez Uniwersytet ŁódzkiIn this work, the application of an innovative, environmentally friendly reduced graphene oxide–glassy carbon (RGO–GC) electrode is described. Using the RGO–GC electrode, basic electrochemical properties (such as the number of protons and electrons involved in an oxidation process, heterogeneous rate constant, diffusion coefficient and electron transfer coefficient) of pindolol (PND) were studied. It was observed that the indole moiety is a part of the pindolol molecule where oxidation takes place. Additionally, a square-wave stripping voltammetric method for the quantitative determination of PND was developed. The influence of various factors such as pH, buffer concentration and SWSV (square wave stripping voltammetry) parameters were studied. The best results in terms of signal shape and intensity were recorded in a BR buffer at pH 5.0. This electroanalytical procedure was used to determine pindolol on the RGO–GC electrode in a concentration range of 1 10 7 to 1 10 5 mol L 1. The precision, repeatability and accuracy of the method were checked. The detection and quantification limits were found to be 2.6 10 8 and 8.6 10 8 mol L 1, respectively. The method has been satisfactorily applied to the determination of pindolol in urine samples and pharmaceutical formulations

Voltammetric behaviour and quantitative determination of pesticide iminoctadine

Publikacja w ramach programu Royal Society of Chemistry "Gold for Gold" 2014 finansowanego przez Uniwersytet ŁódzkiIminoctadine (IOD) was determined in spiked river water samples by square wave voltammetry (SWV) 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 6.5 a signal connected with the catalytic hydrogen evolution reaction was detected at 1.8 V versus Ag/AgCl. Validation of the method was carried out. The LOD and LOQ have been estimated to be 2.6 10 9 mol L 1 and 8.5 10 9 mol L 1 , respectively

Electrochemical and theoretical studies of the interaction between anticancer drug ponatinib and dsDNA

Abstract In this study, electrochemical and theoretical studies were performed to explain the interaction mechanism between ponatinib (PNT), a third generation tyrosine kinase inhibitor, and dsDNA. The electrochemical part was conducted in phosphate-buffered saline (PBS) at physiological pH of 7.4 and in acetate buffer with a pH of 4.7, using square wave voltammetry. A boron-doped diamond electrode was used in a bulk-incubated solution. The theoretical part was investigated using computational methods, such as the semiempirical method PM7 and density functional theory (DFT). Significant differences in the electrochemical behavior of PNT in the presence of DNA confirmed the occurrence of interactions. The results obtained in the acetate buffer strongly suggested the preferential interaction of PNT with guanine residues. However, at physiological pH, it can be concluded that PNT interacts with dGua and dAdo in the dsDNA molecule. These results are consistent with outcomes from the theoretical studies, where quantum-chemical calculations showed that both electrochemically detectable nucleobases form hydrogen bonds with the drug. These bonds appeared to be stronger with guanine than with adenine. According to the computational studies, the dsDNA major groove is the energetically preferred site for the complexation of PNT

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

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)

Současné aplikace elektrod ze stříbrné amalgámy pro analýzu léčiv a vitaminů

The features and applications of silver amalgam electrodes in electroanalysis of pharmaceuticals and vitamins are summarized in this review. The state-of-the-art in the preparation and construction of solid silver amalgam electrodes for prolonged and user-friendly use is presented. Although not as widely spread as other electrode materials, silver amalgam possesses a unique and viable combination of favorable electrochemical properties, which are close to ideal mercury electrodes, non-toxic character, high durability and mechanical stability, if properly prepared. Its capability of conducting the redox processes at highly negative potentials is essential for the analysis of large number of bioactive organic compounds. The review features also overview information for each application in drug or vitamin analysis divided to the sections according to the construction variants of silver amalgam electrodes.V tomto přehledovém článku byly shrnuty vlastnosti a aplikace elektrod ze stříbrné amalgámy pro elektroanalýzu léčiv a vitaminů. Byly prezentovány jednotlivé přístupy při přípravě a konstrukci elektrod z pevné stříbrné amalgámy pro prodloužené a uživatelsky příznivé použití. Review poskytuje informace o jednotlivých aplikacích rozdělené do sekcí podle použité konstrukční varianty stříbrné amalgámové elektrody

Oxidative Grafting of Adrenaline onto Carbon Electrode Surface: Preliminary Studies

In the present work, we performed the optimization of electrografting of adrenaline onto a glassy carbon electrode surface. The cyclic voltammetry technique was used to immobilize the compound on the electrode surface by immersing it in an acidic adrenaline solution. This grafting was achieved by conducting 20 successive CV scans over a wide potential range. The stability of the obtained layer was analyzed using the SWV technique. The conducted research shows that it is possible to create a stable adrenaline layer on the GCE surface using voltammetric techniques. Additionally, once a stable layer was immobilized, its sensitivity to certain metal cations—which cannot be directly detected electrochemically—was verified. After exposing the sensor to designated cationic solutions, there was a significant decrease in the adrenaline signal. This suggests potential future applications in cation determination