New approaches in antibiotics detection: The use of square wave voltammetry

Antibiotics belongs to a class of pharmaceutical compounds widely used due to their effectiveness against bacterial infections. However, if consumed or inappropriately disposed of in the environment can results in environmental and public health problems, because they are considered emerging contaminants and their residues represent damage, whether in the long or short term, to different terrestrial ecosystems, in addition to bringing potential risks to agricultural sectors, such as livestock and fish farming. For this, the development of analytical methods for low-concentration detection and identification of antibiotics in natural waters, wastewaters, soil, foods, and biological fluids is necessary. This review shows the applicability of square wave voltammetry for the analytical determination of antibiotics from different chemical classes and covers a variety of samples and working electrodes that are used as voltammetric sensors. The review involved the analysis of scientific publications from the Science Direct® and Scopus® databases, with scientific manuscripts covering the period between January 2012 and May 2023. Various manuscripts were discussed indicating the applicability of square wave voltammetry in antibiotics detection in urine, blood, natural waters, milk, among other complex samples.

Electrochemical sensor for tricyclic antidepressants with low nanomolar detection limit: Quantitative Determination of Amitriptyline and Nortriptyline in blood

Amitriptyline and its metabolite, Nortriptyline are commonly used tricyclic antidepressant (TCA) drugs that are electrochemically active. In this work, the performance characteristics of a plasticized PVC membrane-coated glassy carbon (GC) electrode are described for the voltammetric quantification of Amitriptyline and Nortriptyline in whole blood. The highly lipophilic Amitriptyline and Nortriptyline preferentially partition into the plasticized PVC membrane where the free drug is oxidized on the GC electrode. The concentrations of the drugs in the membrane are orders of magnitude larger than in the sample solution, resulting in superb limit of detection (LOD) of the membrane-coated voltammetric sensor: 3 nmol/L for Amitriptyline and 20 nmol/L for Nortriptyline. Conversely, hydrophilic components of the sample solution, e.g., proteins, the protein-bound fraction of the drugs, and electrochemically active small molecules are blocked from entering the membrane, which provides exceptional selectivity for the membrane-coated sensor and feasibility for the measurements of Amitriptyline in whole blood. In this work, the concentrations of Amitriptyline and Nortriptyline were determined in whole blood using the sensor and the results of our analysis were compared to the results of the standard HPLC-MS method. Based on our experience, the one-step voltammetric methods with the membrane-coated sensor may become a real alternative to the significantly more complex HPLC-MS analysis.

Polymeric membrane-modified voltammetric sensors for lipophilic analytes with nanomolar detection limit: Key parameters influencing the response characteristics

Thin plasticized PVC membrane-coated glassy carbon working electrodes have been used for the voltammetric measurement of highly lipophilic, electroactive drugs. Compared to conventional working electrodes, these membrane-coated electrodes exhibit remarkable detection limit and selectivity and are less prone to electrode fouling. The unique performance characteristics of these sensors are related to the large partition coefficient of the analyte in the membrane coating where it is oxidized in a non-aqueous membrane phase. To analyze the influence of the key parameters of the response of membrane-coated sensors, we derived theoretical expressions on the voltammetric response of the sensors. In our analysis we considered 1) the partition coefficient (P_mw) of the analyte between the aqueous sample and the organic membrane, 2) the membrane volume to sample volume ratio (V_m/V_w), and 3) the binding constant of constituents in the sample that bind the analyte (K). The results of our theoretical analysis have been tested through voltammetric measurement of highly lipophilic analytes with logP_ow values (logarithm of the partition coefficient between octanol and water) ranging between 0.3 and 7.5. By understanding of the influence of the sensor design parameters on the overall sensor response, these parameters can be tuned for optimized response slope, detection limit, etc., for solving specific analytical tasks.

Voltammetry of local anesthetics: theoretical and practical aspects

Local anesthetics (LAs) are widely used in anesthesiology, ophthalmology, and otolaryngology as well as for treatment of chronic and oncological pain. However, anesthetics can cause adverse effects up to lethal ones. In this work, we cited reviews on chromatographic and spectroscopic methods of local anesthetics determination published earlier, and the main purpose was to review the possibilities and advantages of voltammetric methods used for the LAs determination. The electrochemical behavior, mechanism of LAs transformation on the various working electrodes and analytical parameters of voltammetric methods used for their determination were reviewed in the work. Vast majority of these methods were developed for the most widely used anesthetics in medicine like benzocaine, lidocaine and procaine. Special attention was paid to possible mechanisms of electrochemical oxidation and in some cases reduction of LAs or their derivatives. Voltammetry is used for the determination of LAs in pharmaceutical formulations and in biological fluids. The analytical characteristics in terms of sensitivity, selectivity, reproducibility also were discussed in the article.

Voltammetric sensing of silver nanoparticles on electrodes modified with selective ligands by using covalent and electropolymerization procedures. Discrimination between silver(I) and metallic silver

New electrochemical sensors are described for the rapid quantification of silver nanoparticles (AgNPs). They are based on the immobilization of L-cysteine on a glassy carbon electrode (GCE) and on the formation of electropolymerized oligomers on the GCE. Ligands with amino, sulfur and carboxy functional groups are used that are capable of selectively retaining AgNPs. The experimental conditions for electropolymerizations were optimized for each of four monomers studied: L-lysine, thiophene-3-carboxamide, thionin, and o-phenylene-diamine. The best retention capabilities and conditions for quantification of AgNPs were found for immobilized nanoparticle voltammetry. This method is more sensitive than others based on the sorption of AgNPs from dispersions. These ligands also retain ionic silver species. Hence, Ag(I) and Ag⁰ can be discriminated, and the total silver content can be quantified by stripping voltammetry. The best analytical properties (for dispersions of AgNPs of 40 nm diameter) were found with GCEs carrying electropolymerized L-lysine. Figures of merit include (a) sensitivity of 4.329 ± 0.031 μA μg^-1 mL cm^-2, (b) a detection limit of 0.010 μg mL^-1, and (c) a relative standars deviation of about 7.2% (for n = 4). The poly-L-lysine sensors can also evaluate the size of the AgNPs in the range 20 to 80 nm diameter, owing to displacements of the maximum potential of the voltammetry peaks. Graphical abstractSchematic representation of the quantification of silver nanoparticles (AgNPs) with a glassy-carbon electrode (GCE) modified with electropolymerized poly(L-lysine). AgNPs (and Ag⁺ ions) are selectively preconcentrated in the polymer and determined by differential-pulse stripping voltammetry.

Graphite paste electrodes modified with a sulfo-functionalized metal-organic framework (type MIL-101) for voltammetric sensing of dopamine

The metal-organic frameworks MIL-101 and sulfo-MIL-101 were used to modify graphite paste electrodes (GPEs) to obtain sensors for determination of dopamine (DA). Taking advantage of the catalytic activity of metal-organic frameworks (MOFs) and of the electrical conductivity of graphite, the modified GPEs show enhanced voltammetric responses, and the GPE modified with the sulfo-MOF displays superior sensitivity when operated at a working potential of -0.4 to 0.8 V (vs. Ag/AgCl). The sensor works in the 0.07 to100 μM DA concentration range and has a 43 nM detection limit. It is concluded that the sulfo group provides open sites for efficient electrostatic and hydrogen bonding interactions, which facilitates electron transfer. Graphical abstractSchematic representation of the structure of the sulfo-functionalized MOF (sulfo-MIL-101) and the different voltammetric signals of dopamine at the graphite paste electrodes (GPEs) modified with sulfo-MIL-101 and the parent MOF (MIL-101).

Core-shell hyperbranched chitosan nanostructure as a novel electrode modifier

The present study reports, for the first time, the development and use of core-shell amino-terminated chitosan (Cs) hyperbranched nanoparticles (HBCs-NH₂ NPs) as a novel natural polymer-based electrode modifier for efficient electrochemical systems. The electrochemical activity of the developed HBCs-NH₂ NPs as compared to Cs NPs was identified by standard oxidation-reduction reactions of ferricyanide. The oxidation-reduction peaks height was about twofold higher than the response of Cs-modified electrode. On the other hand, NADH oxidation at the nanostructured surfaces confirmed the electrocatalytic activity where the oxidation of NADH appeared at a lower overpotential (from 805mV to 635mV vs Ag/AgCl). Eventually, a diffusion-controlled process was confirmed from the scan rate effect.

ω-Thio nitrilotriacetic chemically modified gold electrode for iron determination in natural waters with different salinity

The preparation, characterization and analytical application of a chemically modified gold electrode (CME), based on ω-thio nitrilotriacetic acid derivative (N-[5-[[[[20-(acetylthio)-3,6,9-trioxaeicos-1-yl]oxo]carbonyl]amino]-1carboxypentyl]iminodiacetic acid) self-assembled monolayer (SAM), have been described. The electrode has been characterized by electrochemical techniques and tested for its response towards metallic ions, demonstrating to be effective for the determination of ionized iron at sub-μg L(-1) level by differential pulse cathodic stripping voltammetry (DPCSV). The analytical response towards iron in natural water (tap water, marine water) and the interference of ions usually present and chelating agents (humic acids and EDTA as model ligand of high complexing capacity) have been evaluated.

Chronoamperometric estimation of cognac and brandy antioxidant capacity using MWNT modified glassy carbon electrode

Cognac and brandy components are electrochemically oxidized on multi-walled carbon nanotube modified glassy carbon electrode at 0.44 and 0.59 V in 0.1 М phosphate buffer solution pH 3.0. Voltammetric behavior of the main antioxidant constituents of cognac (ellagic and gallic acids, syringaldehyde, coniferaldehyde, vanillin, 5-hydroxymethylfurfural and furfural) has been investigated. The peak at the less positive potential of cognacs is caused by oxidation of gallic acid as well as syringaldehyde- and coniferaldehyde. The second peak corresponds to ellagic acid oxidation. One-step chronoamperometry at 0.59 V for 75 s has been applied for the cognac and brandy antioxidant capacity (AOC) evaluation. Ellagic acid, being the main antioxidant of cognac, has been used as a reference substance. The chronoamperometric response of ellagic acid is linear in the range of 0.66-52.8 µM with the limit of detection and quantification at 0.19 and 0.63 µM, respectively. AOC in ellagic acid equivalents per 100mL of cognac and brandy for different denominations (11 cognacs and 11 ordinary and vintage brandies) has been estimated. AOC of cognacs and brandies increases with the age of the beverages. Positive correlations (r=0.9134-0.9703) with common parameters characterizing antioxidant properties of beverages, in particular antiradical activity, total phenolics content, total antioxidant capacity and ferric reducing power have been observed.