Britton-Robinson Buffer Research Articles

Highly sensitive voltammetric determination of the fungicide fenhexamid using a cost-effective and disposable pencil graphite electrode

A differential pulse voltammetric (DPV) method is proposed for the highly sensitive determination of fenhexamid (FHX) based on both electrooxidation and electroreduction processes using a disposable and cost-effective pencil graphite electrode (PGE). The electrochemical oxidation and reduction mechanisms of FHX at the PGE were elucidated by recording cyclic voltammograms at various pH values of Britton–Robinson buffer (BRB) solutions at a scan rate of 50 mV s−1 and different scan rate values in the range 10–400 mV s−1 at selected pH of BRB (pH 2.0). Differential pulse voltammograms recorded under optimized conditions revealed an oxidation peak of FHX around + 0.65 V and a reduction peak of FHX around + 0.45 V. The DPV analysis of FHX revealed two linear ranges: 0.001–0.01 µmol L−1 and 0.01–5.0 µmol L−1 for the anodic peak, and 0.001–0.1 µmol L−1 and 0.1–5.0 µmol L−1 for the cathodic peak. The limits of detection were 0.34 nmol L−1 and 0.32 nmol L−1 for the anodic and cathodic peaks, respectively. The proposed methodology demonstrated satisfactory selectivity, as selected pesticides, certain electroactive compounds, and cationic species tested did not interfere with the voltammetric determination of FHX, particularly during its reduction. The recovery results, showing values close to 100% obtained from the analysis of real samples spiked with FHX, indicated that this methodology can accurately determine FHX in water and soil samples.Graphical abstract

Synthesis and cyclic voltammetric studies of azo dye compounds derived from 1,5-dihydroxynaphthalene and their application as corrosion inhibitors for carbon steel in hydrochloric acid solution

New bis-azo dyes derived from 1,5-dihydroxynaphthalene were synthesized and characterized by elemental analysis, Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy (1H NMR). These compounds were examined using differential pulse polarography (DPP) and cyclic voltammetry (CV) in Britton-Robinson buffer solutions with pH values ranging from 2 to 12. When the two NN centers of the examined azo compounds were cleaved to form the amine group, the bis-azo group was reduced with the loss of eight electrons, resulting in an irreversible diffusion-controlled cathodic peak. The reduction mechanism was postulated in view of the data obtained was found to be H+, e, e, H+. The application of these azo compounds as corrosion inhibitors for carbon steel in hydrochloric acid solution was investigated and the inhibition efficiency was found to be increasing with both time and concentration, reaching 97 % after 24 hours in the presence of 10−3 M for the three azo compounds. The Langmuir adsorption isotherm indicates that the suppression of corrosion is caused by the inhibitor molecules donating electrons to the empty d-orbitals of the surface of the carbon steel (chemical adsorption), as the calculated Gibbs free energy (∆Gads) is found to be around −40 kJ/mol. The influence of temperature on the parameters of corrosion was examined, and the thermodynamic parameters of corrosion were computed and examined. The results showed that increasing temperature causes increasing of the inhibition efficiency of the tested bis-azo dyes. The order of inhibition efficiency followed their donating affinity which increases in the order p-OCH3 > p-CH3 > m-CH3. Also, the results showed that these compounds causes decrease in entropy, enthalpy and activation energy due to their chemical interaction with the metal surface.

Sensitive and eco-friendly voltammetric detection of galantamine using a screen-printed sensor with a functional boron-doped diamond electrode

The presented study focused on developing and optimizing a modern electroanalytical platform for the direct quantitative determination of galantamine. This work used different voltammetric methods to use a screen-printed sensor with a working boron-doped diamond electrode (SP/BDDE). Beneficial analytical performance for detecting galantamine was achieved in a Britton-Robinson buffer with pH 3.0. The oxidation peaks at 0.92 V and 1.20 V were followed for electrochemical quantification of galantamine. High-resolution mass spectrometry was used for the first time to analyze the products of preparative electrolysis, and a mechanism for the electrochemical oxidation of galantamine was proposed, which describes the demethylation of galantamine and the further oxidation of the hydroxyl group to a ketone group in the galantamine molecule.Coupled with the optimized parameters of differential pulse voltammetry and square-wave voltammetry on the SP/BDDE detected galantamine in two linear ranges (the first range was from 1.22 μM to 10 μM; the second range was from 10 μM to 200 μM), providing the limit of detection and limit of quantification on a micromolar level (0.50 μM and 1.48 μM, respectively). Amperometry and chronoamperometry were employed to develop a rapid detection method for galantamine. In this approach, galantamine can be detected at a level of 1.08 μM (amperometry at the second peak). The selectivity of the optimized amperometric methods was found to be excellent in the presence of ten times higher concentrations of certain interferences. The practical applicability of the SP/BDDE for detecting galantamine was demonstrated through the analysis of pharmaceutical products and human urine samples. The proposed procedure fully complies with the latest requirements of green analytical chemistry.

Environmentally friendly screen-printed electrodes for the selective detection of 4-bromo-2,5-dimethoxyphenethylamine (2C-B) in forensic analysis.

In response to the growing need for sustainable analytical methods, this study explores the repurposing of screen-printed electrodes (SPEs) that would otherwise be discarded. This involves recoating the working electrode surface with a graphite (Gr) and chitosan (CTS) dispersion, creating a reusable SPE (SPE-Gr/CTS). Demonstrating its utility, SPE-Gr/CTS was employed for the detection of 4-bromo-2,5-dimethoxyphenethylamine (2C-B), a phenylethylamine commonly used for recreational proposes. Identifying 2C-B in fluid oral and seized samples is of great interest for forensic and toxicological applications. The 2C-B detection using SPE-Gr/CTS was optimized in Britton-Robinson buffer solution (0.1 mol L-1) at pH 2.0, employing square-wave adsorptive stripping voltammetry. The electrochemical behavior of 2C-B on SPE-Gr/CTS exhibited one irreversible oxidation and a reversible redox process. The proposed method presented a dynamic linear range for 2C-B determination (0.05 to 7.5 μmol L-1) with a low LOD (0.015 μmol L-1). Moreover, the stability of 2C-B electrochemical responses on SPE-Gr/CTS was confirmed using the same or different electrodes (N = 3), with a relative standard deviation of less than 5.0%. Interference studies with seventeen other illicit drugs and adulterants demonstrated that the proposed method is selective for 2C-B detection even in the presence of these substances. Real seized and oral fluid samples containing 2C-B were analyzed using this method, and the results were confirmed by LC-MS. The proposed device demonstrates to be an environmentally friendly and selective sensor for 2C-B detection in forensic analysis, offering a rapid and straightforward screening method for seized and biological samples. In addition, a portable and sensitive determination of 2C-B in forensic samples is presented with minimal sample consumption (50 μL).

Validated Spectrofluorometric Assay for Folic Acid Determination in Pure and Pharmaceutical Forms via Basic Fuchsin Fluorescence Quenching.

A simple, specific, sensitive, rapid, and cost-effective spectrofluorometric method for quantifying folic acid has been developed using basic fuchsin as a fluorescence quenching agent. This method relies on the quenching effect of folic acid on the inherent fluorescence of basic fuchsin, facilitated by their interaction in Britton-Robinson buffer solution at pH 9, leading to the formation of an ion-associated complex. The decrease in fluorescence intensity of basic fuchsin was measured at 730 nm, with excitation at 365 nm. The method demonstrated a linear relationship (R2 = 0.9977) between the quenching fluorescence intensity (ΔF) and folic acid concentration over the range of 4-20 μg/mL, with a detection limit of 0.17 μg/mL. The method showed no significant interference from common excipients found in pharmaceutical tablets. The results obtained were in good agreement with those from high-performance liquid chromatography, with no significant differences in precision or accuracy. This spectrofluorimetric method was successfully applied to determine the folic acid content in various commercial pharmaceutical tablets.

Synthetic Cathinones' Comprehensive Screening and Classification by Voltammetric and Chemometric Analyses: A Powerful Method for On-Site Forensic Applications.

The use of synthetic cathinones (SCs) has increased in recent years, posing significant public health problems due to their adverse effects and potential for fatal poisonings. The structural diversity and rapid emergence of new SC analogues create challenges for law enforcement and drug screening techniques. This work presents for the first time the electrochemical detection of SCs using differential pulse voltammetry (DPV) on a boron-doped diamond electrode (BDDE). We analyzed 15 SCs, including well-known compounds such as mephedrone, methylone, and ephylone, revealing distinct electrochemical profiles with two characteristic reduction peaks (R1 and R2). The method was optimized in Britton-Robinson buffer (0.1 mol L-1, pH 8.0) and demonstrated a high selectivity and sensitivity. Multivariate statistical methods, including principal component analysis and hierarchical cluster analysis, classified SCs into six distinct groups. The DPV optimization and analytical parameter determination, including the limit of detection (LOD), were performed for the least electroactive SC, 4'-methyl-α-pyrrolidinohexanophenone, yielding an LOD of 3.8 μmol L-1, suitable for screening street samples. Interference studies with common illicit drugs and adulterants confirmed the selectivity of the DPV-BDDE method. Preliminary identification of SCs in 46 real seized samples was successfully performed using this method with results validated by liquid chromatography-mass spectrometry (LC-MS). The method also identified three SCs not included in the original set: bupropion, benzylone, and dipentylone. The DPV-BDDE method offers a rapid, robust, and portable approach for the selective screening of SCs in forensic applications, demonstrating significant advantages over traditional colorimetric tests.

Curcumin-Based Molecularly Imprinted Polymer Electropolymerized on Single-Use Graphite Electrode for Dipyridamole Analysis.

A new molecularly imprinted polymer (MIP)-based disposable electrochemical sensor for dipyridamole (DIP) determination was obtained. The sensor was rapidly prepared by potentiodynamic electrochemical polymerization on a pencil graphite electrode (PGE) using curcumin (CUR) as a functional monomer and DIP as a template molecule. After the optimization of the conditions (pH, monomer-template ratio, scan rate, number of cyclic voltammetric cycles applied in the electro-polymerization process and extraction time of the template molecule) for MIP formation, DIP voltammetric behavior at the modified electrode (MIP_PGE) was investigated. DIP oxidation took place in a pH-dependent, irreversible mixed diffusion-adsorption controlled process. Differential pulse voltammetry (DPV) and adsorptive stripping differential pulse voltammetry (AdSDPV) were used to quantify DIP from pharmaceutical and tap water samples. Under optimized conditions (Britton-Robinson buffer at pH = 3.29), the obtained linear ranges were 5.00 × 10-8-1.00 × 10-5 mol/L and 5.00 × 10-9-1.00 × 10-7 mol/L DIP for DPV and AdSDPV, respectively. The limits of detection of the methods were 1.47 × 10-8 mol/L for DPV and 3.96 × 10-9 mol/L DIP for AdSDPV.

Facile prepared high purity Cerium vanadate for simultaneous electrochemical detection of p-nitrophenol and 2,4,6-trichlorophenol

The incomplete inner subshell (i.e., 4f) makes rare-earth elements (REE) different from other elements in the periodic table. Incorporating an atomic number across the lanthanide group merely adds an extra electron to the inner 4f rather than the outer shell. To prove this, we tested Nd and Ce doped vanadates as facile and convenient way for simultaneous detection of para-nitrophenol and 2,4,6-trichlophenol via the electrochemical way over modified glassy carbon (GC) electrode (GC/CeVO4; NdVO4). For the materials preparation convenient single-step hydrothermal procedure was developed and resulting material (CeVO4) demonstrate high grade of crystallinity with average size through the crystalline plain (200) equal to 57.4 nm and absence of any additional phases. GC/CeVO4 electrode was applied for the pioneering study of simultaneous determination of p-nitrophenol (pNP) and 2,4,6-trichlorophenol (TCP) via the SWV method in Britton-Robinson buffer solution at pH5. The developed method of evaluation demonstrate the span of p-nitrophenol calibration graph in range from 0.2 μM to 100 μM with the detection limit 0.058 μM in the presence of 100 μM of 2,4,6-trichlorophenol. The TCP calibration graph comprise concentrations in range from 0.2 μM to 60 μM with the detection limit 0.111 μM in the presence of 100 μM of pNP. Simultaneous determination of pNP and TCP may be performed in range from 0.2 μM up to 60 μM with the limits of detection equal to 0.091 μM for pNP and 0.151 μM for TCP. GC/CeVO4 electrode demonstrate 9.2 % deviation of pNP signal and 11.3 % of TCP signal deviation within 8 cycles of measurement. Interference study was held with K+, Mg2+, Sr2+, ascorbic acid, citric acid, urea, phenol, resorcinol each taken in 10-fold excess, while the electrode demonstrated retention of signal level not less than 75 % of initial. Application of electrode to tap water investigation had shown the 15 % deviation of pNP signal while the TCP signal stays intact. The abovementioned makes GC/CeVO4 electrode promising for the evaluation of aromatics in wastewaters.

Voltammetric and flow amperometric determination of drug guaifenesin in pharmaceutical and biological samples using screen-printed sensor with boron doped diamond electrode

New voltammetric and flow amperometric methods for the determination of guaifenesin (GFE) using a perspective screen-printed sensor (SPE) with boron-doped diamond electrode (BDDE) were developed. The electrochemical oxidation of GFE was studied on the surface of the oxygen-terminated BDDE of the sensor. The GFE provided two irreversible anodic signals at a potential of 1.0 and 1.1 V (vs. Ag|AgCl|KCl sat.) in Britton-Robinson buffer (pH 2), which was chosen as the supporting electrolyte for all measurements. First, a voltammetric method based on differential pulse voltammetry was developed and a low detection limit (LOD = 41 nmol L−1), a wide linear dynamic range (LDR = 0.1–155 μmol L−1), and a good recovery in the analysis of model and pharmaceutical samples (RSD <3.0 %) were obtained. In addition, this sensor demonstrated excellent sensitivity and reproducibility in the analysis of biological samples (RSD <3.2 %), where the analysis took place in a drop of serum (50 μL) without pretreatment and additional electrolyte. Subsequently, SP/BDDE was incorporated into a flow-through 3D printed electrochemical cell and a flow injection analysis method with electrochemical detection (FIA-ED) was developed, resulting in excellent analytical parameters (LOD = 86 nmol L−1, LDR = 0.1–50 μmol L−1). Moreover, the mechanism of electrochemical oxidation of GFE was proposed based on calculations of HOMO spatial distribution and spectroelectrochemical measurements focused on IR identification of intermediates and products.

Eco-Friendly Voltammetric Analysis of Flibanserin with Electropolymerized β-Cyclodextrin on Carbon Sensors

This study developed a cost-effective method to determine flibanserin (FLN) using a screen-printed carbon electrode modified with β-Cyclodextrin polymer (SPCE/β-CD). The electrode was modified in Britton-Robinson buffer at pH 5.0 to enhance FLN’s electrochemical oxidation, with cyclic and differential pulse voltammetry used for detection. Characterization techniques included energy-dispersive X-ray analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The method showed a linear response to FLN concentrations ranging from 5.2 to 80.0 ng ml−1, with a detection limit of 0.004 μM and a quantitation limit of 0.014 μM. The modified electrode demonstrated good sensitivity, reproducibility, and was applied successfully to FLN analysis in spiked human serum and urine samples. An environmental impact assessment was conducted using the Green Analytical Procedure Index, which evaluates the green characteristics of the entire analytical methodology from sample collection to final determination. Additionally, the Analytical Eco-Scale, which assesses the use of organic preparations, procedures, and instruments, demonstrated a favorable green analysis profile. This modified electrode provides a convenient, cost-effective, and eco-friendly approach for determining flibanserin in various matrices.

Reorientation of interfacial water molecules during melting of brain sphingomyelin is associated with the phase transition of its C24:1 sphingomyelin lipids

Melting of brain sphingomyelin (bSM) manifests as a broad feature in the DSC curve that encompasses the temperature range of 25 – 45 °C, with two distinguished maxima originating from the phase transitions of two the most abundant components: C24:1 (Tm,1) and C18:0 (Tm,2). While C24:1/C18:0 sphingomyelin transforms from the gel/ripple phase to the fluid/fluid phase, the dynamics of water molecules in the interfacial layer remain completely unknown. Therefore, we carried out a calorimetric (DSC), spectroscopic (temperature-dependent UV-Vis and fluorescence) and MD simulation study of bSM in the absence/presence of Laurdan® (bSM ± L) suspended in Britton-Robinson buffer with three different pH values, 4 (BRB4), 7 (BRB7) and 9 (BRB9), and of comparable ionic strength (I = 100 mM). According to DSC, T̅m, 1 (≈ 34.5 °C/≈ 32.1 °C) and T̅m, 2 (≈ 38.0 °C/≈ 37.2 °C) of bSM suspended in BRB4, BRB7, and BRB9 in the absence/presence of Laurdan® are found to be practically pH-independent. Turbidity-based data (UV-Vis) detected both qualitative and quantitative differences in the response of bSM suspended in BRB4/BRB7/BRB9 (T̅m: ∼ 35 °C/32.0 ± 0.2 °C/36.4 ± 0.4), suggesting an intricate interplay of weakening of van der Waals forces between their hydrocarbon chains and of increased hydration in the polar headgroups region during melting. The temperature-dependent response of Laurdan® reported a discontinuous, pH-dependent change in the reorientation of interfacial water molecules that coincides with the melting of C24:1 lipids (on average, T̅m (LTC/HTC): ≈ 31.8 °C/30.6 °C/30.5 °C). MD simulations elucidated the impact of Laurdan® on a change in the physicochemical properties of bSM lipids and characterized the hydrogen bond network at the interface at 20 °C and 50 °C.

Electrochemical sensing platform for anticonvulsant drug carbamazepine detection based on graphitic carbon nitride and tetrabutylammonium chloride ionic liquid

The development of a rapid and straightforward electrochemical approach for the quantification of the anticonvulsant drug carbamazepine (CBZ) is herein presented. Carbon paste electrode (CPE) was bulk modified with a type of two-dimensional conjugated polymer, i.e., graphitic carbon nitride (g-C3N4), and additionally with an ionic liquid tetrabutylammonium chloride (TBACl) to obtain advanced electrochemical sensor for CBZ. Synthesized g-C3N4 material was structurally and morphologically characterized by Raman spectroscopic, FTIR, and SEM/EDX methods. CV experiments showed that the resulting electrode (TBACl-g-C3N4-CPE) has an improved electrochemical response compared to unmodified CPE and g-C3N4-CPE due to the synergistic effect of electrode modifiers, as well as that the CBZ oxidation process is irreversible and diffusion-controlled. After optimization steps concerning the amount of electrode modifiers and the selection of pH of the supporting electrolyte, the analytical performance of TBACl-g-C3N4-CPE was investigated by direct anodic square-wave voltammetry (SWV). The most intensive peak of the target analyte was obtained in Britton-Robinson buffer solution at pH 7.0, whereby the developed SWV method was characterized by a linear concentration range of CBZ from 0.42 to 9.31 µmoL L−1, limit of detection (LOD) of 0.13 µmoL L−1, and relative standard deviation lower than 3 %. The interference study showed that TBACl-g-C3N4-CPE exhibits adequate selectivity for CBZ in the presence of ions/compounds commonly present in the urine matrix. The developed sensor was utilized to determine CBZ in pharmaceuticals and spiked human urine sample with excellent recovery and reproducibility, indicating a good application capability of TBACl-g-C3N4-CPE for monitoring CBZ in different matrices.

Voltammetric determination of the antifungal drug posaconazole in the presence of an anionic surfactant on a boron-doped diamond electrode

This study describes a new, fast and simple procedure of electrochemical assay of posaconazole (PCZ), which is currently regarded as one of the most important antifungal agents, recommended in the treatment of systemic infections, effective even against rare and atypical kinds of fungi. PCZ is very effective and safe, displaying much lower toxicity than other traditional antifungal drugs. A new, attractive procedure of assaying the compound on boron-doped diamond (BDD) electrode after cathodic pretreatment in the presence of sodium dodecyl sulfate (SDS) is presented in the work. The anionic surfactant SDS was selected after the comparative analysis of various cationic surfactants. PCZ gave a single irreversible oxidation peak at the potential of 0.59 V. The addition of SDS resulted in an almost 5-fold growth in the value of recorded currents as compared to those observed in the absence of the surfactant. The highest peak was obtained in Britton-Robinson buffer at pH 3.78. The calibration curve of PCZ plotted using the SWV technique was linear in the concentration range from 1.34·10−8 mol/L to 1.44·10−6 mol/L. The limit of detection and limit of quantification were 3.78·10−9 mol/L and 1.14·10−8 mol/L, respectively. The value of relative standard deviation of the measurements did not exceed 4.42 %, which proves good precision of the proposed method. The proposed procedure was successfully used in assaying PCZ in simulated gastric juice.

An affordable and green voltammetric approach for the determination of sotalol in biological, environmental, and pharmaceutical samples

AbstractThis work outlines the development of a voltammetric method for a sensitive, rapid, and environmentally friendly determination of the antihypertensive sotalol (SOT) in several sample types employing the anodically pretreated boron‐doped diamond electrode. Cyclic voltammograms of SOT presented a well‐defined irreversible oxidation peak at 1.21 V (Ag/AgCl (3.0 mol L−1 KCl)) in Britton–Robinson buffer solution (pH 3.0). Figures of merits recommended by the validation guidelines were evaluated for the validation of the present method. Employing differential pulse voltammetry linearity of SOT was obtained in the concentration range of 0.39–4.22 μmol L−1 in 0.1 mol L−1 H2SO4 solution, with a limit of detection of 0.031 μmol L−1. The selectivity of the method was assessed against interferers and show relative standard deviation (RSD) values lower than 6 %. Recovery tests yielded percentages ranging from 93 % to 96 % in urine sample and from 100 % to 107 % in tap water sample. The proposed method was successfully applied in pharmaceutical, environmental, and biological samples offering a suitable green analytical chemistry profile.

Graphite/Aluminum oxide/polylactic acid composite material: A valuable strategy for additively manufacturing cheap and improved electrochemical platforms for sensing sulfamethoxazole in honey samples

Composite materials with properties aimed at the additive manufacturing of affordable electrochemical sensors have received special attention in the scientific scenario. For this reason, we proposed a new composite material based on alumina oxide (Al2O3) and graphite (Gpt) dispersed in polylactic acid (PLA) biopolymer. Various proportions between the materials were studied, and a better compromise between printability and electrochemical performance was obtained using Gpt/Al2O3/PLA (30:10:60% w/w). The electrodes were manufactured using a 3D pen, a portable, user-friendly, and low-cost tool. Characterizations by Raman and infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy indicated that Gpt and Al2O3 were successfully incorporated into the PLA matrix. Preliminary studies using species with well-known electrochemical behavior revealed that Al2O3 positively impacts the electrochemical response of the sensor. As a proof of concept, sulfamethoxazole (SMZ), a low-cost antibiotic widely used in beekeeping practices, was selected as the target analyte, and a simple, fast, and selective method using square wave voltammetry was proposed. Using the 3D-printed Gpt/Al2O3/PLA electrode, a wider linear range (2.0 to 40.0 μmol L−1), a 6.5-fold increase in sensitivity, limits of detection (LOD = 0.4 μmol L−1) and quantification (LOQ = 1.2 μmol L−1) were achieved compared to the Al2O3-free electrode (Gpt/PLA). In addition, the proposed sensor was selective against other antibiotics commonly used in beekeeping practices. Three honey samples were analyzed after simple dilution in 0.12 mol L−1 Britton-Robinson buffer, pH 7.0 (background electrolyte), and recoveries close to 100% as well as statistically comparable results from chromatographic analysis certified the accuracy and reliability of the analysis. The proposed approach is innovative and valuable in contributing to the advancement of additive manufacturing in electrochemical sensing, especially in the on-site analysis of antibiotic species in food, a public health challenge.

Solid Bismuth Drop Electrode – A New Tool for Voltammetric Determination of Electrochemically Reducible Organic Compounds

Solid bismuth drop electrode (SBiDE) is a new working electrode commercially available on the Czech market from 2020 by the company Metrohm. The aim of this work was to verify the applicability of the SBiDE in the voltammetric determination of a model organic substance. According to the available information, this is the very first published work on this topic. Metronidazole (an antibiotic used to treat diseases caused by both Gram-positive and Gram-negative anaerobic bacteria) was chosen in this study as a model drug representing electrochemically reducible biologically active compounds. Under optimum conditions (Britton-Robinson buffer of pH 12.0 used as the supporting electrolyte and no electrochemical regeneration of the working electrode surface), a linear calibration dependence of metronidazole was recorded in the concentration range from 1 to 600 μmol L–1, with the limits of detection (LOD) and quantification (LOQ) of 0.41 μmol L–1 and 1.4 μmol L–1, respectively. The newly developed differential pulse voltammetric (DPV) method has also been successfully applied in the determination of metronidazole in various dosage forms.

Development of an electroanalytical methodology for the identification and quantification of cocaine in samples seized using a carbon paste electrode modified with multi-walled carbon nanotubes

Among the drugs of abuse, cocaine (COC) is the second most commonly used worldwide due to its stimulating and psychoactive effects. Currently, this drug is classified, according to the World Drug Report (WDR), as an illicit substance and is frequently seized by law enforcement agencies. Additionally, it can cause social problems due to its abusive use. This study describes the development of an electroanalytical methodology using square wave voltammetry (SWV) associated with a single electrode of carbon paste modified with 10 % MWCNTs (multi-walled carbon nanotubes) to quantify COC in seized samples containing up to 20% cocaine (low purity index) in the state of Espírito Santo (Brazil). SWV parameters, including Es = 10 mV, a = 30 mV, and f = 15 Hz, were optimized utilizing a Britton-Robinson buffer solution of 0.1 mol/L (pH 10) as a supporting electrolyte through the implementation of experimental design (CCD). COC showed an oxidation peak at approximately 1.0 V, with low limits of quantification and detection (1.90 × 10−6 mol L−1 and 5.75 × 10−7 mol L−1, respectively), in the linear range from 2.36 × 10−6 mol L−1 to 1.38 × 10−5 mol L−1, with the proposed methodology. Thus, this research develops a fast and low-cost technique in favor of the police, allowing the R2 = 99%. The results obtained in the intraday calibration curves present a relatively low standard deviation (RSD < 8%), indicating a good repetition of the value production of an electrode for less than USD 1.42 per analysis.

Powerful Analytical Platform for Diazepam Determination in Pharmaceuticals and Alcoholic Drinks Based on Batch Injection Analysis Coupled with Adsorptive Stripping Voltammetry

The presented study focuses on the development and optimization of a powerful electroanalytical platform for the direct quantification of diazepam (DZP). This innovative approach integrates a batch injection analysis (BIA) system with a screen-printed electrode arrangement employing square-wave adsorptive stripping voltammetry (SWAdSV). The BIA-SWAdSV method underwent a comprehensive evaluation, wherein various experimental and instrumental parameters were systematically examined in detail. Beneficial analytical performance for detecting DZP was attained in Britton-Robinson buffer with pH 6.0, with an amplitude of 75 mV, a frequency of 10 Hz, a deposition potential of –1.2 V, a deposition time of 150 s, an injection volume of 75 μl, a dispensing rate of 7 μl s−1 and without stirring during the deposition step. Under these conditions, the proposed BIA-SWAdSV method demonstrated an adequately broad linear concentration range from 5 μM to 40 μM (R 2 = 0.997) with a micromolar limit of detection (2.0 μM) and a satisfactory precision (RSD = 5.0%). The practical applicability of the newly established and powerful analytical protocol was confirmed through the analysis of pharmaceuticals and a fortified samples of an alcoholic drink (rum) associated with potential criminal activities involving DZP abuse.

Silver Nanoparticle-Embedded Hydrogels for Electrochemical Sensing of Sulfamethoxazole Residues in Meat.

A disposable electrochemical sensor based on silver nanoparticle-embedded cellulose hydrogel composites was developed for sensitive detection of sulfamethoxazole residues in meat samples. Scanning electron microscopy confirmed the porous structure of the cellulose matrix anchored with 20-50 nm silver nanoparticles (AgNPs). Fourier transform infrared spectroscopy and X-ray diffraction verified that the metallic AgNPs coordinated with the amorphous cellulose chains. At an optimum 0.5% loading, the nanocomposite sensor showed a peak-to-peak separation of 150 mV, diffusion-controlled charge transfer kinetics, and an electron transfer coefficient of 0.6 using a ferro/ferricyanide redox probe. Square-wave voltammetry was applied for sensing sulfamethoxazole based on its two-electron oxidation peak at 0.72 V vs. Ag/AgCl in Britton-Robinson buffer of pH 7.0. A linear detection range of 0.1-100 μM sulfamethoxazole was obtained with a sensitivity of 0.752 μA/μM and limit of detection of 0.04 μM. Successful recovery between 86 and 92% and less than 6% RSD was achieved from spiked meat samples. The key benefits of the proposed disposable sensor include facile fabrication, an antifouling surface, and a reliable quantification ability, meeting regulatory limits. This research demonstrates the potential of novel cellulose-silver nanocomposite materials towards developing rapid, low-cost electroanalytical devices for decentralized on-site screening of veterinary drug residues to ensure food safety.

Challenging electroanalytical method for the determination of mirabegron in biological samples and pharmaceutical formulations

A simple, economic, sensitive, and time-saving differential pulse voltammetric (DPV) procedure using nanostructured zinc oxide modified carbon paste electrode (nano ZnO-CPE) in conjunction with an anionic surfactant sodium dodecyl sulfate (SDS) was developed for ultra- sensitive detection of mirabegron (MIR), the most prescribed pharmaceutical drug in treatment of overactive bladder (OAB). The use of nanostructured zinc oxide CPE modifier increased the electrode active surface area as well as improved the process of electron transfer, also it was found that at optimal conditions MIR electrochemical process was both irreversible and diffusion-regulated. The morphological characterization of the fabricated electrode was performed using field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). MIR voltammetric behavior was investigated using Nano ZnO-CPE in different content and electrode compositions. Therefore, ultra-sensitive results were attained with a linearity range of (0.55 to 100.20 ng ml−1) and a low limit of detection (LOD) of 0.51 ng ml−1 and limit of quantification (LOQ) of 1.54 ng ml−1 in a 0.04 M Britton-Robinson (BR) buffer at an adjusted pH of 6.0 with scan rate 100 mV s−1. Furthermore, the proposed approach was successful in measuring MIR with acceptable percentage recoveries (99.81–100.11 %) in pharmaceutical dosage form and varying concentration ranges in biological samples (99.74–100.35 %). The proposed method has been validated using ICH criteria and proven to be accurate and repeatable.