Voltammetric and amperometric determination of N-nitroso antineoplastic drugs at mercury and amalgam electrodes

Electrochemistry as a Powerful Tool for Investigations of Antineoplastic Agents: A Comprehensive Review

Cancer is most frequently treated with antineoplastic agents (ANAs) that are hazardous to patients undergoing chemotherapy and the healthcare workers who handle ANAs in the course of their duties. All aspects related to hazardous oncological drugs illustrate that the monitoring of ANAs is essential to minimize the risks associated with these drugs. Among all analytical techniques used to test ANAs, electrochemistry holds an important position. This review, for the first time, comprehensively describes the progress done in electrochemistry of ANAs by means of a variety of bare or modified (bio)sensors over the last four decades (in the period of 1982-2021). Attention is paid not only to the development of electrochemical sensing protocols of ANAs in various biological, environmental, and pharmaceutical matrices but also to achievements of electrochemical techniques in the examination of the interactions of ANAs with deoxyribonucleic acid (DNA), carcinogenic cells, biomimetic membranes, peptides, and enzymes. Other aspects, including the enantiopurity studies, differentiation between single-stranded and double-stranded DNA without using any label or tag, studies on ANAs degradation, and their pharmacokinetics, by means of electrochemical techniques are also commented. Finally, concluding remarks that underline the existence of a significant niche for the basic electrochemical research that should be filled in the future are presented.

Fast and Sensitive Voltammetric Method for the Determination of Rifampicin on Renewable Amalgam Film Electrode

In this work, a new sensitive voltammetric method for the determination of rifampicin without time-consuming preconcentration is presented. The objective was to develop a simple, fast and sensitive voltammetric procedure for the analysis of rifampicin in pharmaceutical products. The cyclic renewable mercury film silver-based electrode (Hg(Ag)FE) was applied as a working electrode for this purpose. The optimal conditions for the determination of rifampicin were defined, in terms of the composition of supporting electrolyte (including pH) and instrumental parameters (potential and time of deposition, step potential, pulse height). The method was validated resulting in a satisfactory linearity range of 0.4-250.0 µgmL-1; the limits of detection and quantification are 0.12 µgmL-1 and 0.4 µgmL-1, respectively; and the repeatability of the method expressed as RSD is 4.1% (n = 6) with a surface area of 10.9 mm2. The proposed method was successfully applied in the analysis of rifampicin in simple and composed pharmaceutical formulations.

Spironolactone voltammetric determination on renewable amalgam film electrode

In this study a new high sensitive method of spironolactone (SP) determination is proposed using voltammetric technique. As the working electrode amalgam film silver based electrode (Hg(Ag)FE) was applied, that resulted in obtaining low limit of spironolactone detection, ex. for the preconcentration time 45 s obtained detection limit was 4.7·10^-9 mol L^-1 (1.96·10^-6 g L^-1). The linear response of spironolactone signal on mercury film electrode was obtained in the range of concentration from 15·10^-9 to 3.0·10^-6 mol L^-1 and the obtained repeatability measured as RSD was very good, with the value of 2.0% (n = 5; concentration 0.5·10^-6 mol L^-1). The proposed method was successfully applied and validated by studying the recovery in commercially available pharmaceutical formulations containing known amount of spironolactone.

The use of silver solid amalgam electrodes for voltammetric and amperometric determination of nitrated polyaromatic compounds used as markers of incomplete combustion

Genotoxic nitrated polycyclic aromatic hydrocarbons (NPAHs) are formed during incomplete combustion processes by reaction of polycyclic aromatic hydrocarbons (PAHs) with atmospheric nitrogen oxides. 1-Nitropyrene, 2-nitrofluorene, and 3-nitrofluoranthene as the dominating substances are used as markers of NPAHs formation by these processes. In the presented study, voltammetric properties and quantification of these compounds and of 5-nitroquinoline (as a representative of environmentally important genotoxic heterocyclic compounds) have been investigated using a mercury meniscus modified silver solid amalgam electrode (m-AgSAE), which represent a nontoxic alternative to traditional mercury electrodes. Linear calibration curves over three orders of magnitude and limits of determination mostly in the 10(-7) mol L(-1) concentration range were obtained using direct current and differential pulse voltammetry. Further, satisfactory HPLC separation of studied analytes in fifteen minutes was achieved using 0.01 mol L(-1) phosphate buffer, pH 7.0 : methanol (15 : 85, v/v) mobile phase, and C(18) reversed stationary phase. Limits of detection of around 1 · 10(-5) mol L(-1) were achieved using amperometric detection at m-AgSAE in wall-jet arrangement for all studied analytes. Practical applicability of this technique was demonstrated on the determination of 1-nitropyrene, 2-nitrofluorene, 3-nitrofluoranthene, and 5-nitroquinoline in drinking water after their preliminary separation and preconcentration using solid phase extraction with the limits of detection around 1 · 10(-6) mol L(-1).

Metronidazole radical anion formation studied by means of electrochemical impedance spectroscopy

Radiosensitizers belong to the most important class of the cancerostatic drugs. The electrochemical transfer of the first electron to the cytotoxic radiosensitizer Metronidazole (MET) and MET radical anion formation in aprotic medium was studied by means of electrochemical impedance spectroscopy. The heterogeneous electron transfer rate constant for the first reduction of MET (radical anion production) k0 for the redox couple was determined. Similarly, the diffusion coefficient of MET in dimethylformamide was also calculated by impedance measurements using expression for Warburg coefficient and Warburg plot. Moreover, the equivalent circuit for the redox couple MET/MET•– was proposed and its parameters were evaluated using a non-linear least square fitting. Our results, from the electrochemical point of view, also confirm the suitability of MET for the effective treatment of selected types of the cancer.

Influence of the soil organic matter content on voltammetric determination of derivatised glyphosate in herbicide contaminated soils

The method for monitoring of Glyphosate (GP) in soil samples containing different organic matter content based on differential pulse voltammetry at a hanging mercury drop electrode was developed to reach higher sample preparation efficiency, its repeatability and sufficient limits of detection. The soil samples with three different organic matter contents (evaluated as total organic carbon contents 30.7, 13.0 and 6.3 g kg–1) were tested. The decreasing content of organic matter resulted in a decreasing recoveries (86, 78 and 68%, respectively), with RSD around 10%. The GP derivatised to N-nitrosoglyphosate (NO-GP) can be determined using the adopted method with limits of detection around 2 ppm in the soil samples. This method might be further utilized for routine monitoring of the GP in soil samples during investigation of its effect on the soil biota.