Phenylethylamine sensing at the electrified liquid-liquid interface. Can electrochemistry be used to follow the UHT milk spoilage process?

This study involved an investigation into the electrochemical characteristic of a few biogenic amines (BAs) occurring at the polarized interface between two immiscible electrolyte solutions (ITIES) with ion transfer voltammetry (ITV). The main focus of this research was the comprehensive electroanalytical and physicochemical analysis of phenylethylamine (PEA), allowing the determined of the formal Galvani potential of the ion transfer reaction (ΔorgaqΦ'), diffusion coefficients (D), formal free Gibbs energy of the ion transfer reaction (ΔG'aq→org) and water-1,2-dichloroethane partition coefficient (logPwater/DCEPEA). Furthermore, the collected data were employed to calculate analytical parameters, including voltametric detection sensitivity, limits of detection and the target analyte quantification. Moreover, the influence of the presence of 7 other BAs (histamine, spermine, spermidine, putrescine, cadaverine, tyramine and tryptamine) on the recorded signals originating from the PEA ion transfer was checked. The feasibility of the developed method was corroborated through experimentation with milk samples. Additionally, utilizing the devised methodology, an electrochemical assessment of the spoilage progression in milk samples was undertaken.

Heroin detection in a droplet hosted in a 3D printed support at the miniaturized electrified liquid-liquid interface.

Simple sensing protocols for the detection of illicit drugs are needed. Electrochemical sensing is especially attractive in this respect, as its cost together with the analytical accuracy aspires to replace still frequently used colorimetric tests. In this work, we have shown that the interfacial transfer of protonated heroin can be followed at the electrified water-1,2-dichloroethane interface. We have comprehensively studied the interfacial behavior of heroin alone and in the presence of its major and abundant cutting agents, caffeine and paracetamol. To maximally increase developed sensing protocol applicability we have designed and 3D printed a platform requiring only a few microliters of the aqueous and the organic phase. The proposed sensing platform was equipped with a cavity hosting a short section of Ag/AgCl electrode, up to 20 µL of the aqueous phase and the end of the micropipette tip being used as a casing of a fused silica capillary having 25 µm as the internal pore diameter. The volume of the organic phase was equal to around 5 µL and was present inside the micropipette tip. We have shown that under optimized conditions heroin can be detected in the presence of caffeine and paracetamol existing in a sample with 10,000 times excess over the analyte of interest. The calculated limit of detection equal to 1.3 µM, linear dynamic range spanning to at least 50 µM, good reproducibility, and very low volume of needed sample is fully in line with forensic demands.

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.

Determination of quinine in tonic water at the miniaturized and polarized liquid-liquid interface.

In this work we report an electrochemical approach to quantitative and qualitative analysis of quinine (QN) at the interface between two immiscible electrolyte solutions (ITIES). This was done at the macroscopic (macroITIES) and microscopic (µITIES) systems using ion transfer voltammetry (ITV). The linear response of the peak current vs. increasing concentrations of QN at the µITIES was from 2.50 µM to 29.13 µM and the corresponding calculated limit of detection (LOD) for the current signals originating from QN transfer from the aqueous to the organic phase was equal to 0.49 µM. Additionally, the influence of pH (2-12) of the aqueous phase on the recorded QN signals was investigated. We have found that our method is fully applicable for QN direct determination in non-treated tonic water, as confirmed on three different real samples from three different manufacturers. Finally, a number of validation parameters for the developed method are provided and discussed.