Elen Romão Sartori

Electrochemical evaluation of a boron-doped diamond electrode for simultaneous determination of an antihypertensive ternary mixture of amlodipine, hydrochlorothiazide and valsartan in pharmaceuticals

The simultaneous voltammetric determination of a ternary mixture containing antihypertensive drugs amlodipine (AML), hydrochlorothiazide (HCTZ) and valsartan (VAL) by square-wave voltammetry using a cathodically pretreated boron-doped diamond electrode is reported for the first time. Three very well-resolved and reproducible oxidative processes of AML, HCTZ and VAL were found at 0.781 V, 1.14 V and 1.41 V, respectively, in Britton–Robinson buffer solution (pH 5.0). The linearity ranges were 4.9 × 10−7–7.2 × 10−6 mol L−1, 2.9 × 10−6–4.5 × 10−5 mol L−1, and 9.7 × 10−6–1.3 × 10−4 mol L−1 for AML, HCTZ and VAL, with detection limits of 2.3 × 10−7 mol L−1, 7.5 × 10−7 mol L−1, and 6.2 × 10−6 mol L−1, respectively. The proposed method was successfully applied to the simultaneous analysis of these antihypertensive drugs in their combined pharmaceutical tablets available in the market.

Synthesis of CdO nanoparticles using direct chemical precipitation method: Fabrication of novel voltammetric sensor for square wave voltammetry determination of chlorpromazine in pharmaceutical samples

ABSTRACT A chemically modified electrode was constructed and applied to the electrooxidation of the chlorpromazine (CPZ). The oxidation peak potential of the CPZ at a surface of CdO/nanoparticles (NPs) ionic liquid carbon paste electrode (CdO/NPs/IL/CPE) appeared at 695 mV. The CdO/NPs were characterized with different methods such as transmission electron microscope and X-ray diffraction. Under optimized (pH 7.0), linear calibration curves were obtained in the range of 0.1–350 µM for CPZ, which shows adequate for the quantification in real samples. The proposed method was successfully applied to the determination of CPZ in both pharmaceutical and urine samples.

A highly improved method for sensitive determination of amitriptyline in pharmaceutical formulations using an unmodified carbon nanotube electrode in the presence of sulfuric acid

The present paper describes a novel, simple and reliable differential pulse voltammetric method for determining amitriptyline (AMT) in pharmaceutical formulations. It has been described for many authors that this antidepressant is electrochemically inactive at carbon electrodes. However, the procedure proposed herein consisted in electrochemically oxidizing AMT at an unmodified carbon nanotube paste electrode in the presence of 0.1 mol L(-1) sulfuric acid used as electrolyte. At such concentration, the acid facilitated the AMT electroxidation through one-electron transfer at 1.33 V vs. Ag/AgCl, as observed by the augmentation of peak current. Concerning optimized conditions (modulation time 5 ms, scan rate 90 mV s(-1), and pulse amplitude 120 mV) a linear calibration curve was constructed in the range of 0.0-30.0 μmol L(-1), with a correlation coefficient of 0.9991 and a limit of detection of 1.61 μmol L(-1). The procedure was successfully validated for intra- and inter-day precision and accuracy. Moreover, its feasibility was assessed through analysis of commercial pharmaceutical formulations and it has been compared to the UV-vis spectrophotometric method used as standard analytical technique recommended by the Brazilian Pharmacopoeia.

Simultaneous Voltammetric Determination of Antihypertensive Drugs Amlodipine and Atenolol in Pharmaceuticals Using a Cathodically Pretreated Boron-Doped Diamond Electrode

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.

Simple and rapid determination of loratadine in pharmaceuticals using square-wave voltammetry and a cathodically pretreated boron-doped diamond electrode

The electrochemical behavior and determination of antihistaminic drug loratadine using a cathodically pretreated boron-doped diamond electrode (BDDE) are proposed. This is the first voltammetric method using a carbon-based electrode material. The anodic peak potential for loratadine at the BDDE was 1.67 V (vs. Ag/AgCl (3.0 mol L−1 KCl)) by cyclic voltammetry in a 0.50 mol L−1 HClO4 solution, whereas at the glassy carbon electrode (GCE), no peak potential was observed, due to the narrow potential window of this electrode. Using the square-wave voltammetric technique (f = 50 Hz, a = 40 mV and ΔES = 2 mV), the obtained analytical curve was linear for loratadine concentrations ranging from 0.98 to 19 μmol L−1. This simple, rapid and green analytical method was successfully applied to the determination of loratadine in pharmaceutical formulations. The results were in close agreement, with a 95% confidence level, with those obtained using comparative spectrophotometric method.

Electrochemical study of the antiplatelet agent ticlopidine and its voltammetric determination in pharmaceutical and urine samples using a boron-doped diamond electrode

In the present study, the electrochemical behavior of ticlopidine was investigated by cyclic voltammetry, square-wave voltammetry and differential pulse voltammetry using a cathodically pretreated boron-doped diamond electrode. Ticlopidine exhibited one well developed and irreversible oxidation peak suitable for analytical purposes at about 0.95 V (vs. Ag/AgCl 3.0 mol L−1 KCl) in BR buffer solution (pH 5.0). The electrode reaction of the analyte was found to be a diffusion-controlled process. At optimized differential pulse voltammetric parameters (modulation amplitude of 150 mV, scan rate of 10 mV s−1 and modulation time of 10 ms), the obtained analytical curve was linear for the ticlopidine concentration range of 3.9 to 38.4 μmol L−1 with a detection limit of 0.66 μmol L−1. The influence of possible interfering compounds was studied as well. The proposed method was applied with success in the determination of ticlopidine in pharmaceutical and urine samples with good accuracy and precision.

Vanadato de bismuto sintetizado por combustão em solução na presença de diferentes combustíveis: síntese, caracterização e estudo da atividade fotocatalítica

In this manuscript, a BiVO4 semiconductor was synthesized by solution combustion synthesis using different fuels (Alanine, Glycine and Urea). Also, the Tween® 80 surfactant was added during synthesis. BiVO4 was characterized by XRD, SEM and diffuse reflectance spectroscopy. Photocatalytic activity was evaluated by the discoloration of methylene blue at 664 nm under UV-visible light irradiation. According to XRD, the monoclinic phase of BiVO4 was obtained for the samples. The smallest particle size and highest kobs value were observed for the BiVO4/alanine sample, which promoted greater demethylation of methylene blue.

A simple square-wave voltammetric method for the determination of scopolamine in pharmaceuticals using a boron-doped diamond electrode

A simple procedure is described for the determination of scopolamine by square-wave voltammetry using a cathodically pretreated boron-doped diamond electrode. Cyclic voltammetry studies indicate that the oxidation of scopolamine is irreversible at a peak potential of 1.59 V (vs. Ag/AgCl (3.0 mol L-1 KCl)) in a 0.50 mol L–1 sulfuric acid solution. Under optimized conditions, the analytical curve obtained was linear (r = 0.9996) for the scopolamine concentration range of 1.0 to 110 µmol L–1, with a detection limit of 0.84 µmol L–1. The method was successfully applied to the determination of scopolamine in pharmaceutical formulations with minimum sample preparation.

Evaluation of a Multi-Walled Carbon Nanotube-Hemin Composite for the Voltammetric Determination of Hydrogen Peroxide in Dental Products

A simple, low cost sensor was developed for the voltammetric determination of hydrogen peroxide in mouthwash and dental whitening gel based on multi-walled carbon nanotubes incorporated with hemin. The sensor showed electrocatalytic activity toward the reduction of hydrogen peroxide in 0.05 mol L−1 Tris-HCl buffer solution (pH 7.0) using cyclic voltammetry. The optimum composition of paste was 20:10:70% (m/m/m) (multi-walled carbon nanotubes:hemin:mineral oil). A linear plot of the square root of scan rate vs. cathodic peak current showed that reduction of hydrogen peroxide is diffusion controlled. Using linear sweep voltammetry, the analytical curve ranged from 0.2 up to 1.4 mmol L−1 (r = 0.9996) with a sensitivity of 3.62 × 10−2 mA mol−1 L. The limits of detection and quantification were found to be 12.5 µmol L−1 and 41.7 µmol L−1, respectively. The developed method was applied for hydrogen peroxide determination in dental formulations. The results were compared with a volumetric method as a reference technique. No significant differences at the 95% level (paired student t test) were observed, thus demonstrating the accuracy of the sensor for the analysis of real samples.

Boron-doped diamond electrode: a modification-free platform for sensitive square-wave voltammetric determination of indapamide hydrochloride

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.