Nitrazepam and 7-aminonitrazepam studied at the macroscopic and microscopic electrified liquid-liquid interface.

Two benzodiazepine type drugs, that is, nitrazepam and 7-aminonitrazepam, were studied at the electrified liquid-liquid interface (eLLI). Both drugs are illicit and act sedative in the human body and moreover are used as date rape drugs. Existence of the diazepine ring in the concerned chemicals structure and one additional amine group (for 7-aminonitrazepam) allows for the molecular charging below their pKa values, and hence, both drugs can cross the eLLI interface upon application of the appropriate value of the Galvani potential difference. Chosen molecules were studied at the macroscopic eLLI formed in the four electrode cell and microscopic eLLI formed within a microtip defined as the single pore having 25 µm in diameter. Microscopic eLLI was formed using only a few µL of the organic and the aqueous phase with the help of a 3D printed cell. Parameters such as limit of detection and voltammetric detection sensitivity are derived from the experimental data. Developed methodology was used to detect nitrazepam in pharmaceutical formulation and both drugs (nitrazepam and 7-aminonitrazepam) in spiked biological fluids (urine and blood).

Electroanalytical study of five carbosilane dendrimers at the interface between two immiscible electrolyte solutions.

This work is focused on the electroanalytical study of a family of five imidazolium-terminated carbosilane dendrimers (from generation G1 to G3) at the polarized liquid-liquid interface formed between water and 1,2-dichloroethane solutions. All dendrimers with permanently and positively charged imidazolium groups located at the periphery within the branched carbosilane core were found to be electrochemically active. Based on the concentration and scan rate dependencies we have concluded that these molecules undergo interfacial ion transfer processes accompanied by interfacial adsorption/desorption rather than the electrochemically induced interfacial formation of the macromolecule-anion (tetrakis(4-chlorophenyl)borate) from the organic phase complex. Also, we report several physicochemical and electroanalytical parameters (e.g. diffusion coefficients, LODs, and detection sensitivities) for the studied family of dendrimers. Our work aims to contribute to the understating of the interaction between branched macromolecules and biomimetic interfaces.

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.

Electroreduction of Bi(III) Ions at a Cyclically Renewable Liquid Silver Amalgam Film Electrode in the Presence of Methionine.

The catalytic influence of methionine (Mt) on the electroreduction of Bi(III) ions on the novel, cyclically renewable liquid silver amalgam film electrode (R-AgLAFE) in a non-complexing electrolyte solution was examined. The presence of methionine leads to a multistep reaction mechanism, where the transfer of the first electron is the rate limiting step, which is the subject of catalytic augmentation. The catalytic activity of methionine is a consequence of its ability to remove water molecules from the bismuth ion coordination sphere, as well as to form active complexes on the electrode surface, facilitating the electron transfer process.

Molecularly imprinted polymer film grafted from porous silica for efficient enrichment of steroid hormones in water samples.

Steroid hormones as endocrine disrupting compounds can interfere with the functioning of hormonal systems of organisms and thus affect the health and reproduction of humans and wildlife. Unfortunately, these types of harmful endocrine disrupting compounds have been found in a variety of environmental samples at very low concentrations. Therefore, a simple, fast, and efficient method for enrichment of water samples is needed. A molecularly imprinted solid-phase extraction combined with high performance liquid chromatography coupled with diode array detection was developed for the determination of six steroid hormones, such as estrone, 17-ß-estradiol, estriol, 17-α-ethinylestradiol, progesterone, and testosterone in water samples. The recoveries obtained in the proposed method were in the range of 78.7-101.3%. Matrix effect below 20% suggests that the quantitative and qualitative results of the analysis were not significantly affected by the matrix. The results show that molecularly imprinted polymers based on spherical silica gel had the potential to be a highly innovative and selective sorbent. The proposed method was proved to be applicable for molecularly imprinted solid-phase extraction in selective and reliable extraction and enrichment of steroid hormones in environmental water samples.

Fused Silica Microcapillaries Used for a Simple Miniaturization of the Electrified Liquid-Liquid Interface.

Short pieces of fused silica capillary tubing were used to support an electrified liquid-liquid interface. A methyl deactivated silica capillary having a diameter of 25 µm was filled with 1,2-dichloroethane solution and served as the organic part of the liquid-liquid interface. A nondeactivated fused silica capillary having a diameter of 5, 10, or 25 µm was filled with an aqueous HCl solution and served as the aqueous part of the electrochemical cell. For the latter, silanization of the capillary interior with chlorotrimethylsilane allowed for a successful phase reversal. All capillaries were characterized by ion transfer voltammetry using tetramethylammonium cation as a model ion. This simple, fast, and low-cost miniaturization technique was successfully applied for detection of the antibiotic ofloxacin.

Electrochemical study of the fungicide acibenzolar-s-methyl and its voltammetric determination in environmental samples.

The electrochemical behavior of new generation fungicide acibenzolar-s-methyl (S-methyl 1,2,3-benzothiadiazole-7-carbothioate, ASM) on the hanging mercury drop electrode (HMDE) was investigated using square wave adsorptive stripping voltammetry. This method of determination is based on the irreversible reduction of ASM at the HMDE. The well-defined ASM peak was observed at -0.4 V (vs. Ag/AgCl) in BR buffer at pH 2.2. The reduction peak current was proportional to concentration of ASM from 1.0 × 10(-8) to 6.0 × 10(-8) mol L(-1) with detection and quantification limit 3.0 × 10(-9) and 1.0 × 10(-8) mol L(-1), respectively. The applicability of the developed method for analysis of spiked samples of tap water, river water, and soil is illustrated. The effect of adsorption on the mercury electrode was studied in detail using the AC impedance method. Possible interferences with other common pesticides and heavy metal ions were examined. Clarification of the electrode mechanism was made using cyclic voltammetry (CV) technique.

Advanced Electrode Materials Dedicated for Electroanalysis.

The development of advanced electrode materials has significantly enhanced the capabilities of electrochemical devices, enabling their application in diverse fields such as environmental monitoring, medical diagnostics, food safety, and industrial processes [...].

Incorporation of Bismuth(III) Oxide Nanoparticles into Carbon Ceramic Composite: Electrode Material with Improved Electroanalytical Performance in 4-Chloro-3-Methylphenol Determination.

In this study, a carbon ceramic electrode (CCE) with improved electroanalytical performance was developed by bulk-modifying it with bismuth(III) oxide nanoparticles (Bi-CCE). Characterization of the Bi-CCE was conducted employing atomic force microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. Comparative analysis was conducted using an unmodified CCE. The findings proved that the incorporation of Bi2O3 nanoparticles into the CCE significantly altered the morphology and topography of the ceramic composite, and it improved the electrochemical properties of CCE. Notably, the Bi-CCE demonstrated a prolonged operational lifespan of at least three months, and there was a high reproducibility of the electrode preparation procedure. The developed Bi-CCE was effectively employed to explore the electrochemical behavior and quantify the priority environmental pollutant 4-chloro-3-methylphenol (PCMC) using CV and square-wave voltammetry (SWV), respectively. Notably, the developed SWV procedure utilizing Bi-CCE exhibited significantly enhanced sensitivity (0.115 µA L mol-1), an extended linearity (0.5-58.0 µmol L-1), and a lower limit of detection (0.17 µmol L-1) in comparison with the unmodified electrode. Furthermore, the Bi-CCE was utilized effectively for the detection of PCMC in a river water sample intentionally spiked with the compound. The selectivity toward PCMC determination was also successfully assessed.

Comparative electrochemical study of veterinary drug danofloxacin at glassy carbon electrode and electrified liquid-liquid interface.

This work compares the electroanalytical performance of two electroanalytical systems based on (1) the glassy carbon electrode (GCE), and (2) the electrified liquid-liquid interface (eLLI), for the detection of fluoroquinolone antibiotic-danofloxacin (DANO). Our aim was to define the optimal conditions to detect the chosen analyte with two employed systems, extract a number of electroanalytical parameters, study the mechanism of the charge transfer reactions (oxidation at GCE and ion transfer across the eLLI), and to provide physicochemical constants for DANO. Detection of the chosen analyte was also performed in the spiked milk samples. To the best of our knowledge, this is the first work that directly compares the electroanalytical parameters obtained with solid electrode (in this case GCE) and eLLI. We have found that for DANO the latter provides better electroanalytical parameters (lower LOD and LOQ) as well as good selectivity when the milk was analyzed.

Fabrication and Characterization of an Electrochemical Platform for Formaldehyde Oxidation, Based on Glassy Carbon Modified with Multi-Walled Carbon Nanotubes and Electrochemically Generated Palladium Nanoparticles.

This study outlines the fabrication process of an electrochemical platform utilizing glassy carbon electrode (GCE) modified with multi-walled carbon nanotubes (MWCNTs) and palladium nanoparticles (PdNPs). The MWCNTs were applied on the GCE surface using the drop-casting method and PdNPs were produced electrochemically by a potentiostatic method employing various programmed charges from an ammonium tetrachloropalladate(II) solution. The resulting GCEs modified with MWCNTs and PdNPs underwent comprehensive characterization for topographical and morphological attributes, utilizing atomic force microscopy and scanning electron microscopy along with energy-dispersive X-ray spectrometry. Electrochemical assessment of the GCE/MWCNTs/PdNPs involved cyclic voltammetry (CV) and electrochemical impedance spectroscopy conducted in perchloric acid solution. The findings revealed even dispersion of PdNPs, and depending on the electrodeposition parameters, PdNPs were produced within four size ranges, i.e., 10-30 nm, 20-40 nm, 50-60 nm, and 70-90 nm. Additionally, the electrocatalytic activity toward formaldehyde oxidation was assessed through CV. It was observed that an increase in the size of the PdNPs corresponded to enhanced catalytic activity in the formaldehyde oxidation reaction on the GCE/MWCNTs/PdNPs. Furthermore, satisfactory long-term stability over a period of 42 days was noticed for the GCE/MWCNTs/PDNPs(100) material which demonstrated the best electrocatalytic properties in the electrooxidation reaction of formaldehyde.

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.

Improved procedure for square-wave voltammetric sensing of fenhexamid residues on blueberries peel surface at the anodically pretreated boron-doped diamond electrode.

BACKGROUND: Fungicide fenhexamid (FH) has a high residual concentration on fruits and vegetables, thus, it is of high importance to monitor the level of FH residues on foodstuff samples. So far, the assay of FH residues in selected foodstuff samples has been conducted by electroanalytical methods on sp2 carbon-based electrodes that are well-known to be susceptible to severe fouling of the electrodes surfaces during electrochemical measurements. As an alternative, sp3 carbon-based electrode such as boron-doped diamond (BDD) can be used in the analysis of FH residues retained on the peel surface of foodstuff (blueberries) sample. RESULTS: In situ anodic pretreatment of the BDDE surface was found to be the most successful strategy to remediate the passivated BDDE surface by FH oxidation (by)products, and the best validation parameters, i.e., the widest linear range (3.0-100.0 µmol L-1), the highest sensitivity (0.0265 µA L µmol-1) and the lowest limit of detection (0.821 µmol L-1), were achieved on the anodically pretreated BDDE (APT-BDDE) in a Britton-Robinson buffer, pH 2.0, using square-wave voltammetry (SWV). The assay of FH residues retained on blueberries peel surface was performed on the APT-BDDE using SWV, and the obtained concentration of FH residues of 6.152 µmol L-1 (1.859 mg kg-1) was found to be below the maximum residue value fixed for blueberries by the European Union regulations (20 mg kg-1). SIGNIFICANCE AND NOVELTY: In this work, a protocol based on a very easy and fast foodstuff sample preparation procedure combined with the straightforward pretreatment approach of the BDDE surface was elaborated for the first time for the monitoring of the level of FH residues retained on the peel surface of blueberries samples. The presented reliable, cost-effective, and easy-to-use protocol could find its application as a rapid screening method for the control of food safety.

Square-wave voltammetry of human blood serum.

A study on voltammetric analysis of blood serum diluted in a phosphate buffer is presented using advanced square-wave voltammetry at an edge plane pyrolytic graphite electrode. The results demonstrate that even in a complex medium like human blood serum, electrochemical characterization can be achieved through the use of advanced voltammetric techniques in conjunction with an appropriate commercially available electrode, such as the edge plane pyrolytic graphite electrode, which boosts superior electrocatalytic properties. Without undergoing any chemical treatment of the serum sample, the square-wave voltammetry technique reveals, for the first time, the electrode reactions of uric acid, bilirubin, and albumin in a single experiment, as represented by well-defined, separated, and intense voltammetric signals. All electrode processes are surface-confined, indicating that the edge plane sites of the electrode serve as an ideal platform for the competitive adsorption of electroactive species, despite the extensive chemical complexity of the serum samples. The speed and differential nature of square-wave voltammetry are crucial for obtaining an outstanding resolution of the voltammetric peaks, maintaining the quasi-reversible nature of the underlying electrode processes, while reducing the impact of follow-up chemical reactions that are coupled to the initial electron transfer for all three detected species, and minimizing fouling of the electrode surface.

Square wave adsorptive stripping voltammetric determination of diazinon in its insecticidal formulations.

The pesticide diazinon was determined in its insecticidal formulations by square wave adsorptive stripping voltammetry. The method of its determination is based on the irreversible reduction reaction at the hanging mercury drop electrode. The optimal signal was detected at -1.05 V vs. Ag/AgCl in Britton-Robinson buffer at pH 4.4. Various parameters such as pH, buffer concentration, frequency, amplitude, step potential, accumulation time, and potential were investigated to enhance the sensitivity of the determination. The highest response was recorded at an accumulation potential -0.4 V, accumulation time 60 s, amplitude 75 mV, frequency 100 Hz, and step potential 5 mV. The pesticide electrochemical behavior was considered under experimental conditions. The electroanalytical procedure enabled diazinon determination in the concentration range 4.0 × 10(-8)-3.9 × 10(-7) mol L(-1) in supporting electrolyte. The detection and quantification limit were found to be 1.1 × 10(-8) and 3.7 × 10(-8) mol L(-1), respectively. The method was applied successfully in the determination of the active ingredients in the insecticidal formulations Diazinon 10GR and Beaphar 275.

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.

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.

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.

Selected Spectroscopic Techniques for Surface Analysis of Dental Materials: A Narrative Review.

The presented work focuses on the application of spectroscopic methods, such as Infrared Spectroscopy (IR), Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy, Ultraviolet and Visible Spectroscopy (UV-Vis), X-ray spectroscopy, and Mass Spectrometry (MS), which are widely employed in the investigation of the surface properties of dental materials. Examples of the research of materials used as tooth fillings, surface preparation in dental prosthetics, cavity preparation methods and fractographic studies of dental implants are also presented. The cited studies show that the above techniques can be valuable tools as they are expanding the research capabilities of materials used in dentistry.