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Duloxetine hydrochloride (DUL) is an antidepressant drug that is being increasingly consumed and so, it is classified as an emerging pollutant. As it is found at very low concentration in the envir...

The synthesis of a self-doped TiO2 nanotubes (SD-TNT) electrode and its potential applicability as a sensing platform electrode for voltammetric determination of methylene blue (MB) dye is reported. Highly ordered TiO2 nanotubes vertically oriented to the titanium surface were grown and the electrochemical doping did not change the morphology of the TNT. Raman spectroscopy demonstrated that the electrochemical doping of TNT promoted a blue shift of the Eg1 mode (from 152 to 158 cm−1) which results in an increased conductivity due to the phonon confinement resultant from the formation of non-stoichiometry Ti3+ donor states. The structural changes allowed the application of SD-TNT as a voltammetric sensor of MB without any UV irradiation. The SD-TNT electrode allowed an efficient quantification of MB, with a limit of detection of 0.48 and 0.90 μmol L−1 when considered the oxidation and reduction peak, respectively. Then, SD-TNT electrode was applied to the monitoring of MB concentration during electro-Fenton oxidation. MB removal fitted well with pseudo-first-order kinetics, suggesting a constant formation of •OH radicals and oxidation of MB. These results revealed that the SD-TNT is a versatile, simple, and promising material for the voltammetric determination of synthetic dyes.

Electroanalytical chemistry plays a very important role concerning the development of environmentally friendly and time-saving analytical methods. This work reports the first voltammetric determination of bisacodyl (BIS) using boron-doped diamond electrode (BDDE). On the cathodically pretreated BDDE, BIS presented an irreversible and diffusion controlled anodic peak at 1.55 V (vs Ag/AgCl (3.0 mol L–1 KCl)) in BR buffer solution (pH 5.0). Using optimized experimental conditions, the anodic current was linear with the BIS concentration range of 1.00–44.0 μmol L–1, with limit of detection of 0.343 μmol L–1. The viability of the proposed method was successfully evaluated by quantification of BIS in commercial pharmaceutical formulations and the accuracy of the developed analytical procedure was statistically proven by comparison with a validated spectrophotometric method.

In this paper, diltiazem hydrochloride (DTZ) was electrochemically determined on cathodically pretreated boron-doped diamond electrode. The sustainable method showed potential of application using two supporting electrolytes, evaluating two different oxidation peaks of the drug. For voltammetric determination of DTZ, all operating parameters of square-wave voltammetry were optimized and analytical curves were constructed. The voltammetric method was in-house validated in terms of linearity, limit of detection, limit of quantification, precision, accuracy and selectivity. The pharmaceutical samples were analyzed by the official method and the results were statistically similar to those obtained by the voltammetric method. The totally aqueous voltammetric procedure was also applied to the determination of DTZ in biological fluids with excellent recovery values.

A photoelectrochemical biosensing strategy for the highly sensitive detection of the flavonoid rutin was developed by synergizing the photoelectrocatalytic properties of hematite (α-Fe2O3) decorated with palladium nanoparticles (PdNPs) and the biocatalysis towards laccase-based reactions. The integration of α-Fe2O3.PdNPs with a polyphenol oxidase as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the photoactive biocomposite can generate a stable photocurrent, which was found to be directly dependent upon the concentration of rutin. Under the optimal experimental conditions, the cathodic photocurrent, measured at 0.33 V vs. Ag/AgCl, from the square-wave voltammograms presented a linear dependence on the rutin concentration within the range of 0.008–30.0 × 10−8 mol L−1 (sensitivity: 1.7 μA·(× 10−8 M−1)·cm−2), with an experimental detection limit (S/N = 3) of 8.4 × 10−11 mol L−1. The proposed biosensor device presented good selectivity towards rutin in the presence of various organic compounds and inorganic ions, demonstrating the potential application of this biosensing platform in complex matrices. This bioanalytical device also exhibited excellent operational and analytical properties, such as intra-day (standard deviation, SD = 0.21%) and inter-day (SD = 1.30%) repeatability, and long storage stability (SD = 2.80% over 30 days). Graphical abstract

A new protocol for the analysis of the azo-dye carmoisine (CMS) is presented by coupling differential pulse voltammetry (DPV) with a cathodically pretreated boron-doped diamond electrode (CPT-BDDE), in phosphate buffer solution (pH 2.0). The CMS presented diffusion-controlled oxidation and reduction peaks at +0.88 and −0.15 V vs Ag/AgCl, respectively. The effect of the pretreatment conditions, pH, and supporting electrolytes were evaluated to the voltammetric determination of CMS. Under optimized conditions, the differential pulse voltammetric signals for CMS were linear over the concentration range of 0.059–1.31 μmol L−1 and 0.010–0.079 μmol L−1 with limits of detection of 7.0 and 3.0 nmol L−1, for the anodic and cathodic processes respectively. The method was precise for CMS determination (RSD

In this work a crude laccase preparation from Botryosphaeria rhodina MAMB-05 was employed to construct an electrochemical biosensor using nanostructured carbon black. The biosensor was evaluated by differential pulse voltammetry under optimized conditions and was utilized in the determination of epinephrine (EPN). The biosensor’s storage stability was evaluated and was found to be stable over seven consecutive days with a reduction of only 7.0% in the EPN response. Under the optimum conditions developed, the biosensor provided a linear current response for the concentration of EPN in the range from 4.98 to 285 μM. The biosensor was successfully applied for determining EPN in pharmaceutical-grade EPN injection samples, and in synthetic cerebrospinal fluid, demonstrating its promising analytical performance in drug analysis.

In this work, a simple and sensitive voltammetric method for simultaneous determination of antihypertensive drugs amlodipine besylate (AML) and ramipril (RMP) is described. A cathodically pretreated boron-doped diamond electrode (CP-BDDE) was employed wherein AML and RMP were irreversibly oxidized at 0.68 and 1.70 V (vs. Ag/AgCl (3.0 mol L−1 KCl)), respectively, in Britton–Robinson buffer solution (pH 6.0). Under optimized instrumental parameters of differential pulse voltammetry, the oxidation current of AML and RMP linearly increased in the concentration range of of 0.99–14 and 0.29–1.9 μmol L−1, obtaining limits of detection of 0.26 and 0.08 μmol L−1, respectively. The feasibility of the proposed method was successfully assessed by simultaneous quantification of these drugs in commercially available pharmaceutical formulations and rat blood serum samples. The results obtained further verify the fact that the CP-BDDE coupled with the differential pulse voltammetric technique may constitute an electroanalytical platform for fast simultaneous determination of these analytes in pharmaceutical formulations and biological samples.

A boron-doped diamond electrode (BDDE) was employed for indapamide hydrochloride (IND) determination. IND presented an irreversible and diffusion-controlled oxidation peak at 0.53 V in 0.01 mol L−1 H2SO4 by cyclic voltammetry. To develop the voltammetric method, the effect of electrochemical pretreatment of BDDE, pH of supporting electrolyte, type of electrolyte and its concentration were evaluated. Under optimized instrumental parameters of square-wave voltammetry, the IND current was linear over the concentration range of 0.099–4.3 μmol L−1, with limit of detection of 56 nmol L−1. The method was successfully applied to commercial tablets, and the obtained results were statistically similar to those obtained by a spectrophotometric method. Additionally, the determination of IND was accomplished in synthetic cerebrospinal fluid and tap water. The method proved to not suffer from matrix interference with excellent recoveries.

An innovative electroanalytical method has been described for the simultaneous determination of amlodipine besylate (AML) and atorvastatin calcium (ATOR) using the square-wave voltammetry and an anodically pretreated boron-doped diamond electrode. Two very well-resolved and reproducible oxidation peaks for AML and ATOR were obtained in Britton-Robinson buffer solution (pH 4.0). Under the optimum analytical experimental conditions, the method exhibits linear responses to AML and ATOR in the concentration ranges 2.0 – 28 and 1.0 – 50 µmol L−1, respectively, with detection limits of 0.028 and 0.38 µmol L−1, respectively. The proposed novel method was applied in the simultaneous determination of AML and ATOR content in combined dosage forms and the accuracy was attested by means of comparison with those data obtained from high performance liquid chromatography at a 95% confidence level (paired t-test). DOI: http://dx.doi.org/10.17807/orbital.v9i4.973

An advanced, simple and rapid voltammetric method for a quaternary mixture determination of antihypertensive drugs, namely amlodipine besylate (AML), amiloride hydrochloride (AMI), hydrochlorothiazide (HCTZ) and atenolol (ATN), is described. An anodically pretreated boron-doped diamond electrode (using + 0.5 A cm− 2 during 30 s in 0.5 mol L− 1 H2SO4) was employed for square-wave voltammetric determination of these drugs with very well-resolved and reproducible oxidative peaks at 0.68, 0.89, 1.04 and 1.21 V (vs Ag/AgCl (3.0 mol L− 1 KCl)), respectively, in ammonium buffer solution (pH 9.0). Using optimized experimental conditions, the corresponding peaks heights increased linearly within the concentration range of 0.90–31, 8.7–125, 29–260 and 11–91 μmol L− 1 with detection limit of 0.30, 0.09, 0.08 and 0.06 μmol L− 1 for AML, AMI, HCTZ and ATN, respectively. The viability of the proposed method was successfully assessed by simultaneous quantification of the studied drugs in commercially available pharmaceutical formulations and also in spiked tap water sample with the recovery values ranged from 93.9 to 104%. The accuracy of the developed protocol was proven statistically by comparison with high performance liquid chromatography as a reference (comparative) method. The accomplished results fortify the fact that the boron-doped diamond electrode in connection with the square-wave voltammetric technique may constitute an advanced electroanalytical platform for simple and rapid simultaneous determination of various biologically active substances to replace chemically modified electrodes, especially in drug sensing.

This work presents the development of a novel voltammetric method for a sensitive, simple, fast and eco-friendly determination of tadalafil (TDL) using a cathodically pretreated boron-doped diamond electrode (CP-BDDE). Using cyclic voltammetry of TDL, this drug presented one irreversible and well resolved oxidation process at 0.905 V (vs Ag/AgCl (KCl 3.0 mol L −1 )) in Britton-Robinson buffer solution (pH 4.0). A scan rate study demonstrated that TDL transport toward CP-BDDE is diffusion controlled and one proton and one electron are involved in its electrooxidation. Employing square-wave voltammetry under optimized parameters, there was a linear dependence of peak current and TDL concentration in the range of 0.15–1.28 μmol L −1 with a detection limit of 19.5 nmol L −1 . The proposed method was successfully applied in TDL determination in pharmaceutical formulations. The results obtained with the voltammetric method were not statistically different from the comparative spectrophotometric method, at a 95% confidence level.

Made available in DSpace on 2022-04-28T19:30:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-20 The present work describes the performance of a new voltammetric sensor based on the modification of glassy carbon electrodes (GCE) with carbon black (CB) and botryosphaeran (BOT) (CB-BOT/GCE) for the electroanalytical determination of cyclobenzaprine. BOT is a fungal exocellular (1→3)(1→6)-β-ᴅ-glucan, which was used to improve the adherence of CB onto the surface of GCE. The electrochemical characterisation was performed by electrochemical impedance spectroscopy which showed an improvement in the transfer of electrons on the surface of the sensor developed in relation to the unmodified (bare) GCE. The voltammetric behaviour of cyclobenzaprine was studied using bare GCE, BOT/GCE, CB/GCE, and CB-BOT/GCE. All electrodes presented an oxidation peak (+ 1.0 V) for cyclobenzaprine, while the cyclobenzaprine peak intensity on CB-BOT/GCE was found to be 480% higher than the bare GCE. Through employing square-wave voltammetry, the analytical curve was found to be linear over the concentration range of 2.0 to 20.6 μmol L−1 (in 0.1 mol L−1 NaCl solution) with a detection limit (based on 3-sigma) of 0.63 μmol L−1. The developed electrochemical sensor exhibited excellent sensitivity and selectivity and was successfully applied for the voltammetric determination of cyclobenzaprine in pharmaceutical, biological, and environmental samples for the first time using the CB-BOT/GCE electrochemical sensing platform. Departamento de Química Centro de Ciências Exatas Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, 445 Km 380 Faculty of Science and Engineering Manchester Metropolitan University, Chester Street Departamento de Química e Bioquímica Escola de Ciência e Tecnologia Universidade do Estado de São Paulo Programa de Pós-Graduação em Ciências Fisiológicas Departamento de Ciências Fisiológicas Centro de Ciências Biológicas Universidade Estadual de Londrina Beta-Glucan Produtos Farmoquímicos EIRELI UTFPR Câmpus Londrina, Lote 24A, Bloco Zircônia, Avenida João Miguel Caram 731

In this work, we employed multiple linear regression analyses to satisfactorily determine cold symptoms treatment drugs paracetamol, phenylephrine hydrochloride, and loratadine in pharmaceutical formulations with combined dosage and spiked human urine sample. All the drugs are irreversibly oxidized on the boron-doped diamond electrode (BDDE) in diffusion-controlled oxidation processes with well-separated potentials in acidic media. A square-wave voltammetric (SWV) method was developed for their simultaneous determination in 0.1 mol L–1 H2SO4 and simple and multiple linear regression analyses were compared as calibration methods for SWV data. Precision and selectivity were also studied. The high concentration ratio between paracetamol and the other two drugs being minor components in the formulated dosage forms caused interference in their voltammetric responses. An assay based on multiple linear regression equations considering these multiple effects revealed statistically the same results as those obtained by a comparative HPLC-UV method at a 95% confidence level. We demonstrated that multiple linear regression provided adequate recovery for the determination of PAR, PHE, and LOR in spiked human urine sample. The developed SWV method is a very fast, low-cost, and environmentally friendly alternative to the routine simultaneous analysis of PAR, PHE, and LOR performed by HPLC-UV.

The present study describes a convenient method for the individual determination of antihypertensive drug metoprolol (MTP) and its association with hydrochlorothiazide (HCTZ) using a cathodically pretreated boron-doped diamond (BDD) electrode and differential pulse voltammetry (DPV). Two very well-resolved and reproducible oxidative processes of HCTZ and MTP were found at 1.11 V and 1.32 V (vs Ag/AgCl (3.0 mol L−1 KCl)), respectively, in lactate buffer solution (pH 4.0). Under the optimum analytical experimental conditions, the voltammetric method exhibited linear response for individual determination of MTP in the concentration range 0.38–22 μmol L−1, with detection limit of 0.034 μmol L−1, while for a simultaneous determination of HCTZ and MTP, the concentrations range were 0.51–18.7 and 1.23–22.8 μmol L−1, with detection limit of 0.376 and 0.077 μmol L−1 for HCTZ and MTP, respectively. The individual and simultaneous methods were successfully applied in the determination of HCTZ and MTP content in several pharmaceutical formulations, whose accuracy was attested by good agreement of the results (paired t-test at a 95% confidence level) with those obtained using high performance liquid chromatography. In order to indicate that the method is of potential application in biological fluids adequate recovery results were obtained for the determination of HCTZ and MTP in urine samples.

In this work we propose the use of statistical mixture design in the construction of a biosensor device based on graphite oxide, platinum nanoparticles and biomaterials obtained from Botryosphaeria rhodina MAMB-05. The biosensor was characterized by electrochemical impedance spectroscopy. Under optimized experimental parameters by factorial design, the biosensor was applied to the voltammetric determination of chlorogenic acid (CGA) measured as 5-O-caffeoylquinic acid (5-CQA). The biosensor response was linear (R2 = 0.998) for 5-CQA in the concentration range 0.56–7.3 µmol L−1, with limit of detection and quantification of 0.18 and 0.59 µmol L−1, respectively. The new biosensing device was applied to quality control analysis based upon the determination of CGA content in specialty and traditional coffee beverages. The results indicated that specialty coffee had a significantly higher content of CGA. Principal component analysis of the voltammetric fingerprint of brewed coffees revealed that the laccase-based biosensor can be used for their discrimination.

In this work, we explored the efficiency of the use of the pretreated boron-doped diamond electrode (BDDE) coupled to electroanalytical techniques for the individual determination of pravastatin (PRAV) and its association with acetylsalicylic acid (ASA). The voltammetric behavior of PRAV and ASA was investigated by cyclic voltammetry showing irreversible and diffusion-controlled oxidation processes for both analytes, regardless of the type of BDDE pretreatment. Under the optimized conditions (cathodically pretreated BDDE and phosphate buffer solution, pH 4.0), the analytical response for PRAV was linear over the range from 1.0 to 30 μmol L−1 for individual determination using amperometry, obtaining a limit of detection (LOD) of 0.102 μmol L−1. For simultaneous determination of PRAV and ASA, (using the anodically pretreated BDDE in 0.3 mol L−1 H2SO4 solution), the responses were linear over the range of 1.08–16.4 μmol L−1 for PRAV and 3.96–42.75 μmol L−1 for ASA using SWV, obtaining a LOD of 0.204 and 0.078 μmol L−1, respectively. The methods were successfully applied to pharmaceutical formulations, synthetic urine and tap water samples.

In this paper, an alternative voltammetric method for the determination of elemental sulphur in cosmetic products is presented. It is based on the decrease of triphenylphosphine oxidation current in the presence of elemental sulphur by using a glassy carbon electrode. A solution of 2% (m/v) acetic acid and 0.6 mol L-1 sodium acetate in methanol was used as a supporting electrolyte. The experimental conditions for indirect determination of elemental sulphur were established. Using square-wave voltammetry, the analytical curve was linear in the elemental sulphur concentration range of 9.94-271 μmol L-1, with a detection limit of 2.59 μmol L-1. The method was successfully applied to determine elemental sulphur in soap bars and anti-acne cream, without any preliminary sample treatment, therefore, it is shortened and simplified. The results obtained with the indirect voltammetric method were not statistically different in comparison with a titrimetric one, at a 95% confidence level. Additionally, excellent recovery percentages were obtained, proving no matrix interferences.

A glassy carbon electrode was modified with a TiO2-gold nanoparticle hybrid integrated with multi-walled carbon nanotubes in a dihexadecylphosphate film (TiO2-Au NP-MWCNT-DHP/GCE) and applied to amperometric determination of ascorbic acid (AA). The modified sensor displays fast charge transfer and shows an irreversible anodic behavior for AA by cyclic voltammetry. Under optimal experimental conditions and using amperometry at 0.4 V, the analytical curve presented a statistical linear concentration range for AA from 5.0 to 51 μmol L-1, with a limit of detection of 1.2 μmol L-1. The electrode was successfully applied to the determination of AA in pharmaceutical and fruit juice without the need for major pretreatment of samples. Graphical abstract Schematic of a new sensing platform for ascorbic acid (AA). It is based on a glassy carbon electrode (GCE) modified with TiO2-Au nanoparticles integrated into carbon nanotubes in a dihexadecylphosphate film. The sensor was applied to amperometric determination of AA in juice and pharmaceutical samples.

The simultaneous voltammetric determination of antihypertensive drugs amlodipine besylate (AML) and atenolol (ATN) using a cathodically pretreated boron-doped diamond electrode (CP-BDDE) is reported for the first time. The anodic peak potentials of AML and ATN at a CP-BDDE were found to be 0.727 and 1.32 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in phosphate buffer (pH 7.0), respectively, by cyclic voltammetry. It was observed that the CP-BDDE possesses improved performance for the simultaneous determination of AML and ATN when compared to other carbon-based electrodes in these conditions. Using square-wave voltammetric technique, the obtained analytical curves were linear in the concentration range from 2.9-33 µmol L-1 for AML and 9.8-190 µmol L-1 for ATN, with limits of detection of 0.17 and 0.22 µmol L-1, respectively. The proposed method was successfully applied to the simultaneous determination of AML and ATN in pharmaceutical samples.