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.

Interfacial Deposition of Titanium Dioxide at the Polarized Liquid-Liquid Interface.

The interfacial polycondensation of titanium dioxide was studied at the bare and fiberglass membrane supported polarized liquid-liquid interface (LLI). Titanium dioxide synthesis was derived from the titanium (IV) tetrabutoxide (initially dissolved in the 1,2-dichloroethane) interfacial hydrolysis followed by its condensation. Experimental parameters, such as the pH of the aqueous phase and the influence of titanium alkoxide concentration in the organic phase on the electrochemical signal and material morphology, were investigated. The latter was achieved with fiberglass membranes used as the LLI support during TiO2 interfacial deposition. Cyclic voltammetry was used for the in situ studies, whereas scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared spectroscopy were used during ex situ examination. The interfacial polycondensation reaction could be studied using electrified LLI and resulted in the material being a TiO2 film alone or film decorated with particles.

Illicit drugs street samples and their cutting agents. The result of the GC-MS based profiling define the guidelines for sensors development.

In this work, we have focused on the profiling of 5647 street samples covering marijuana, common and new recreational illicit drugs. All samples were analyzed using gas chromatography-mass spectrometry (GC-MS) technique. In total we have identified 53 illicit drugs with Δ-9-tetrahydrocannabinol (THC), amphetamine, N-ethylhexedrone, 3,4-methylenedioxy methamphetamine (MDMA), 4-chloromethcathinone (4-CMC), α-pyrrolidinoisohexaphenone (α-PHiP), cocaine, and 4-chloroethcathinone (4-CEC) being most commonly found and making 38.5, 17.8, 15.5, 8.0, 3.5, 2.7, 2.1, and 2.0% of the total studied pool, respectively. Except for methadone, all analyzed street samples were spiked with at least one cutting agent. Caffeine was the most frequently found adulterating addition present in around 33% (excluding marijuana) of the analyzed samples. Other identified cutting agents make an impressive group of more than 160 compounds. Finally, we have tabulated, illustrated, and discussed presented data in a view of smart and portable sensors development.

Voltammetric study of cefotaxime at the macroscopic and miniaturized interface between two immiscible electrolyte solutions.

The electrochemical behavior of cefotaxime (CTX+) was investigated at the polarized macro- and micro-interface between two immiscible electrolyte solutions (ITIES) by cyclic voltammetry and alternating current voltammetry. Miniaturization was achieved with fused silica microcapillary tubing entrapped in a polymeric casing. Scanning electron microscopy (SEM) was employed for the fabricated LLI support characterization. Voltammetric investigation of CTX+ at macro- and µ-ITIES allowed the determination of many physicochemical parameters, such as formal Galvani potential of the ion transfer reaction ([Formula: see text]), diffusion coefficients (D), formal free Gibbs energy of the ion transfer reaction (∆G'aq → org), and water-1,2-dichloroethane partition coefficient ([Formula: see text]). Additionally, based on the results obtained the analytical parameters including voltammetric sensitivity, limits of detection and the limits of quantification (in micromolar range) were calculated. The applicability of the developed procedures was verified in spiked still mineral and tap water samples.

Improved electroanalytical characteristics for the determination of pesticide metobromuron in the presence of nanomaterials.

In the present work, bare ultra trace graphite electrode (UTGE), UTGE modified with multi-walled carbon nanotubes (UTGE-MWCNTs), and UTGE modified with graphene nanoplatelets (UTGE-GNPs) were considered as working electrodes. For the first time, the UTGEs were modified with MWCNTs and GNPs by simple and fast drop-casting approach (the whole procedures take no more times than ca. 30 min). The comprehensive microscopic and electrochemical characterization of the unmodified and the modified UTGEs was conducted by means of atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. The prepared electrodes were further applied for the analytical purposes, and the procedures for the square-wave voltammetric (SWV) determination of pesticide metobromuron (Mbn) using the bare UTGE, the UTGE-MWCNTs, and the UTGE-GNPs were developed. For the first time, this compound was electrochemically investigated. The SWV measurements were performed in Britton-Robinson buffer (B-R) solution at pH 2.0 as a supporting electrolyte. SWV parameters, i.e. amplitude, frequency, and step potential, were optimized. The linear relationships between peak current vs. increasing concentrations of Mbn were defined using the bare UTGE, the UTGE-MWCNTs, and the UTGE-GNPs, and the limits of detection were calculated (0.13, 0.11, 0.048 µmol L-1, respectively). The analytical parameters determined from calibration curves indicate similar sensitivity on all tested electrodes, however, the widest linearity range as well as the lowest LOD and LOQ values were achieved on the UTGE modified with GNPs. The utility of the proposed method with the UTGE-GNPs was verified by the quantitative analysis of Mbn in soil samples with satisfactory results (recovery of 99.1%). Furthermore, the impact of possible interferences was tested and evaluated, and obtained results proved good selectivity of the proposed method.

ß-Cyclodextrins incorporated multi-walled carbon nanotubes modified electrode for the voltammetric determination of the pesticide dichlorophen.

In this work, a glassy carbon electrode modified with ß-cyclodextrins and multi-walled carbon nanotubes (ß-CDs/MWCNTs/GCE) was constructed and applied for the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the pesticide dichlorophen (Dcp). For the first time, this compound was electrochemically investigated. The voltammetric measurements were conducted in phosphate buffer (PBS) at pH 6.5 as a supporting electrolyte, and SWAdSV technique parameters were optimized. A linear calibration curve in the wide concentration range from 5.0 × 10-8molL-1 to 2.9 × 10-6molL-1 was obtained. Excellent analytical performance in terms of limit of detection (LOD) of 1.4 × 10-8molL-1 was achieved. The utility of the proposed method was verified by the quantitative analysis of Dcp in Pilica River water samples with satisfactory results. The characterization of modified electrodes was conducted by means of atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). Moreover, in this work, the dissociation constants (pKa) of Dcp using potentiometric pH titration were estimated. The stoichiometry of the Dcp-ß-CDs inclusion complex formed in solution was determined by proton nuclear magnetic resonance (1H NMR) spectroscopy, and a binding constant (ß2) was estimated from NMR titration studies.

Electrochemical determination of closantel in the commercial formulation by square-wave adsorptive stripping voltammetry.

ABSTRACT: In this paper, the square-wave adsorptive stripping voltammetric (SWAdSV) determination of the veterinary drug closantel using a renewable silver amalgam film electrode (Hg(Ag)FE) is presented. As observed in SWAdSV, closantel provided one well-shaped reduction peak suitable for analytical purposes at potential ca. -1.4 V in the Britton-Robinson (B-R) buffer at pH 7.0. At optimal conditions, the SWAdSV response of Hg(Ag)FE for determining closantel was linear over two concentration ranges of 5.0 × 10-8 to 2.0 × 10-7 mol dm-3 and 2.0 × 10-7 to 1.2 × 10-6 mol dm-3 with a detection limit of 1.1 × 10-8 mol dm-3. In addition, a relevance of the developed SWAdSV method was successfully verified by the quantitative analysis of closantel in the commercial formulation Closamectin Pour-On with satisfactory results (RSD = 5.8%, recovery = 101.8%). The results showed that the developed procedure can be adequate for screening purposes. Also, the electrochemical behavior of closantel was characterized by cyclic voltammetry, and it was found that closantel exhibited a quasi-reversible behavior with cathodic peak on the forward scan at ca. -1.4 V and anodic peak on the reverse scan at ca. -1.35 V vs. Ag/AgCl in B-R buffer, pH 7.0. As the obtained results showed that the electrode mechanism of closantel is controlled by the adsorption, the effect of adsorption was studied using the electrochemical impedance spectroscopy technique.

Electrodes Modified with Composite Layers Based on Poly(3,4-ethylenedioxythiophene) as Sensors for Paracetamol.

Two sensors for paracetamol were obtained on the basis of a GC electrode modified with poly(3,4-ethylenedioxythiophene) (PEDOT). The first sensor was a GC electrode modified with a conductive composite layer of PEDOT doped with poly(4-lithium styrenesulfonic acid) (PSSLi), and the second one was a GC electrode modified by a composite of PEDOT doped with PSSLi and multiwall carbon nanotubes (MWCNT). A conductive PEDOT polymer film was used as an electron mediator with a rich electron cloud. Both sensors were developed for the determination of paracetamol (ACOP) in the presence of interference compounds. Differential pulse voltammetry (DPV) and adsorptive stripping differential pulse voltammetry (AdsDPV) were applied as analytical methods. The modified electrodes were successfully employed for the determination of ACOP in a pharmaceutical formulation.