Voltammetric behavior of erythromycin ethylsuccinate at a renewable silver-amalgam film electrode and its determination in urine and in a pharmaceutical preparation

Effect of Bi(iii)-to-metal ion concentration ratios on stripping voltammetric response of bismuth-film glassy carbon electrodes

The effect of Bi-to-metal ion concentration ratio (c Bi/c M ratio) on key evaluation indicators, including sensitivity, precision, and cathodic potential range, has been investigated for the determination of Cd and Pb at in situ prepared bismuth film electrodes. Unlike the usual recommendation of at least a 10-fold excess of Hg(ii) for anodic stripping experiments at in situ prepared mercury film electrodes, it is found that the c Bi/c M ratios in the 1-10 range are sufficient to obtain a high determination sensitivity, but that the signal decreases significantly when the ratio exceeds 40. Further analysis shows that the precision of the analytical results is good when the c Bi/c M ratio is in the range of 5-10. The precision is even better in the range of 10-20, but too high a ratio cannot further improve the precision of the results. Therefore, it is recommended to keep the c Bi/c M in the range of 5 to 40 to balance the sensitivity and precision in detection. The study also finds that the optimum cathodic potential range is related to the total concentration of metal ions. Therefore, for metals susceptible to hydrogen evolution (e.g., zinc), additional consideration should be given to inhibiting the hydrogen evolution reaction when selecting the c Bi/c M ratio. This work is the first to investigate the effect of the c Bi/c M ratio on the morphology and thickness of deposits using EIS, SEM, and AFM. It is found that increasing the c Bi/c M ratio leads to an increase in the coverage and thickness of the bismuth film on the electrode surface, which enhances the sensitivity of the determination. However, this change is also accompanied by an increase in the electrode resistance, resulting in a significant decrease in signal when the ratio is too large. In addition, when the c Bi/c M ratio is <5, the precision of the bismuth film electrode is relatively poor due to the rapid increase of the bismuth coverage on the electrode surface. The uneven thickening of the deposit also affects the cathodic potential range. Based on these findings, standard curves with c Bi/c M ratios ranging from 5-25 are prepared and successfully applied to the analysis of river water and wastewater.

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.

Impregnation of biochar with montmorillonite and its activation for the removal of azithromycin from aqueous media

An inexpensive and environmentally friendly composite synthesized from rice husk, impregnated with montmorillonite and activated by carbon dioxide, was investigated for the removal of azithromycin from an aqueous solution. Various techniques were used to characterize adsorbents in detail. The sorption process was primarily regulated by the solution pH, pollutant concentration, contact duration, adsorbent dose, and solution temperature. The equilibrium data were best analyzed using the nonlinear Langmuir and Sips (R² > 0.97) isotherms, which revealed that adsorption occurs in a homogenous manner. The adsorption capacity of pristine biochar and carbon dioxide activated biochar-montmorillonite composite was 33.4 mg g^-1 and 44.73 mg g^-1, respectively. Kinetic studies identified that the experimental data obeyed the pseudo-second-order and Elovich models (R² > 0.98) indicating the chemisorption nature of adsorbents. The thermodynamic parameters determined the endothermic and spontaneous nature of the reaction. The ion exchange, π-π electron-donor-acceptor (EDA) interactions, hydrogen-bonding, and electrostatic interactions were the plausible mechanisms responsible for the adsorption process. This study revealed that a carbon dioxide activated biochar-montmorillonite composite may be used as an effective, sustainable, and economical adsorbent for the removal of azithromycin from polluted water.

Developing a generally applicable electrochemical sensor for detecting macrolides in water with thiophene-based molecularly imprinted polymers

Our screening data revealed the threat macrolide antibiotics, especially azithromycin (AZN), posed to human health with its increasing occurrence in water environment. The electrochemical sensor based on molecularly imprinted polymer (MIP) is a promising platform that caters for the next generation of intelligent wastewater treatment plants (WWTPs) by virtue of its wide tolerance to water from all sources and in-situ monitoring. However, low initiation potentials of cross-linking monomers contributed by the electron-rich circumstance allowed them to usurp sites designed for functional monomers when electrically stimulated, leading to an unsatisfactory binding capacity. Another uncertainty is that multiple reaction sites of cross-linking monomers granted them complex polymerization routes and made it difficult to ensure the consistency of preparation. Serval monomers had been investigated with electrochemical tools and the performance of sensors constructed with these monomers were compared in this study. Based on the results, we proposed a protocol in which a novel functional monomer possessing a stronger electron-donating group, phenyl, was adopted to compete for the dominance in electropolymerization. Beyond that, the cross-linking monomer was modified with electron-withdrawing groups to raise its initiation potential. A monothiophene with a moderate initiation potential was also recruited as the linker to address the steric hindrance. In this way, polymerization proceeded in a specific order. It is worth mentioning that the Marangoni flow is an ideal tool to deal with the Coffee-ring deposition while drop-casting. The resulting sensor showed good performance with a limitation of detection (LOD) of 0.120 μM for AZN and a satisfactory selectivity, and the design can be applied to constructing sensors for a variety of macrolide antibiotics.

Brief Overview of Frequently used Macrolides and Analytical Techniques for their Assessment

Background:

Macrolide antibiotics are known as versatile broad-spectrum antibiotics. Macrolides belong to the oldest group of antibacterial agents. The macrolides which are frequently used for clinical purposes are broadly categorized in three classes depending on the number of membered macrocyclic lactone ring. These three classes actually consist of 14, 15 or 16 atoms in macrocyclic lactone ring which are linked through glycosidic bonds. Erythromycin, azithromycin clarithromycin and roxithromycin are frequently used to control against bacterial infections.

Methods:

The quality assurance and quality controls are important tasks in the pharmaceutical industries. Consequently, to check the quality of drugs, there is a strong need to know about alternative analytical methods for the routine analysis. Many methods have been reported in the literature for the quantitative determination of erythromycin, clarithromycin, azithromycin and clarithromycin in pharmaceutical formulations and biological samples.

Results:

This review will cover a brief introduction of erythromycin, azithromycin, clarithromycin and roxithromycin as well as analytical techniques for their assessment. Each developed method has its own merits and demerits.

Conclusion:

Any accurate method could be used for the quality control and quality assurance of macrolide antibiotics according to the availability, performance and procedure of selected instrument as well as skill and expertise of the analyst.

A Review: New Trends in Electrode Systems for Sensitive Drug and Biomolecule Analysis

Drug and biomolecule analysis with high precision, fast response, not expensive, and user-friendly methods have been very important for developing technology and clinical applications. Electrochemical methods are highly capable for assaying the concentration of electroactive drug or biomolecule and supply excellent knowledge concerning its physical and chemical properties such as electron transfer rates, diffusion coefficients, electron transfer number, and oxidation potential. Electrochemical methods have been widely applied because of their accuracy, sensitivity, cheapness, and can applied on-site determinations of various substances. The progress on electronics has allowed developing reliable, more sensitive and less expensive instrumentations, which have significant contribution in the area of drug development, drug and biomolecule analysis. The developing new sensors for electrochemical analysis of these compounds have growing interest in recent years. Screen-printed based electrodes have a great interest in electrochemical analysis of various drugs and biomolecules due to their easy manufacturing procedure of the electrode allow the transfer of electrochemical laboratory experiments for disposable on-site analysis of some compounds. Paper based electrodes are also fabricated by new technology. They can be preferred due to their easy, cheap, portable, disposable, and offering high sensitivity properties for many application field such as environmental monitoring, food quality control, clinical diagnosis, drug, and biomolecules analysis. In this review, the recent electrochemical drug and biomolecule (DNA, RNA, µRNA, Biomarkers, etc.) studies will be presented that involve new trend disposable electrodes.

Voltammetric Techniques for the Analysis of Drugs using Nanomaterials based Chemically Modified Electrodes

Background:

Electroanalytical techniques play a very important role in the areas of medicinal, clinical as well as pharmaceutical research. Amongst these techniques, the voltammetric methods for the determination of drugs using nanomaterials based chemically modified electrodes (CMEs) have received enormous attention in recent years. This is due to the sensitivity and selectivity they provide on qualitative as well as quantitative aspects of the electroactive analyte under study. The aim of the present review was to discuss the work on nanomaterials based CMEs for the analysis of drugs covering the period from 2000 to present employing various voltammetric techniques for different classes of the drugs.

Methods:

The present review deals with the determination of different classes of drugs including analgesics, anthelmentic, anti-TB, cardiovascular, antipsychotics and anti-allergic, antibiotic and gastrointestinal drugs. Also, a special section is devoted for enantioanalysis of certain chiral drugs using voltammetry. The detailed information of the voltammetric determination for the drugs from each class employing various techniques such as differential pulse voltammetry, cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, stripping voltammetry, etc. are presented in tabular form below the description of each class in the review.

Results:

Various nanomaterials including carbon nanotubes, graphene, carbon nanofibers, quantum dots, metal/metal oxide nanoparticles, polymer based nanocomposites have been used by researchers for the development of CMEs over a period of time. The large surface area to volume ratio, high conductivity, electrocatalytic activity and biocompatibility make them ideal modifiers where they produce synergistic effect which helps in trace level determination of pharmaceutical, biomedical and medicinal compounds. In addition, macrocyclic compounds as chiral selectors have been used for the determination of enantiomeric drugs where one of the isomers captured in the cavities of chiral selector shows stronger binding interaction for one of the enantiomorphs.

Conclusion:

arious kinds of functional nanocomposites have led to the manipulation of peak potential due to drug - nanoparticles interaction at the modified electrode surface. This has facilitated the simultaneous determination of drugs with almost similar peak potentials. Also, it leads to the enhancement in voltammetric response of the analytes. It is expected that such modified electrodes can be easily miniaturized and used as portable, wearable and user friendly devices. This will pave a way for in-vivo onsite real monitoring of single as well as multi component pharmaceutical compounds.