scholarly journals Disposable stencil-printed carbon electrodes for electrochemical analysis of sildenafil citrate in commercial and adulterated tablets

2021 ◽  
Author(s):  
Danielly Rocha ◽  
Habdias Silva-Neto ◽  
Laísa Oliveira ◽  
Shellyda Souza ◽  
Mário Santana ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Graphite Powder ◽  
Electrochemical Analysis ◽  
Sildenafil Citrate ◽  
Carbon Electrodes ◽  
Heterogeneous Electron Transfer ◽  
Linear Behavior ◽  
Electron Transfer Rate Constant ◽  
3D Printed

Forensic studies are extremally important to investigate suspected adulterations of consumable products, such as Viagra®. This report describes the determination of sildenafil citrate (SC) in commercial and adulterated tablets based on square-wave voltammetry (SWV) measurements using disposable stencil-printed carbon electrodes. The conductive ink used for the manufacture of integrated electrodes was produced by combining graphite powder and glass varnish. To promote a reusable strategy for limiting the geometric area of the electrodes, a 3D-printed holder was constructed. Detailed morphological and electrochemical characterization studies revealed well-defined graphite flakes incorporated on the polymeric substrate and a faster heterogeneous electron-transfer rate constant (Ks = 1.3 × 10–3 cm s–1). Based on the analytical performance, a linear behavior was observed in a SC concentration range from 1 to 20 µmol L–1 with limit of detection equal to 0.2 µmol L–1. The selectivity of the proposed method was evaluated and the presence of potentially interfering compounds like phosphate, lactose, paracetamol and tadalafil and no difference higher than 15% was observed. The analysis of SC was performed in commercial and seized tablets and the achieved values were 50 ± 1 mg for Viagra® tablet, 54 ± 1 mg for generic formulations 38 ± 1 mg for seized tablet. In addition, the proposed method offered satisfactory accuracy (98.2 – 102.0%) no noticeable matrix effect. Lastly, considering the achieved results, the use of stencil-printed carbon electrodes and SWV has demonstrated to be a powerful and robust analytical tool for forensic investigations.

Electrochemical Analysis of Sulfamethoxazole by Differential Pulse Voltammograms Method

2020 ◽  
Author(s):  
Ahmad Khalaf Alkhawaldeh
Keyword(s):  
Limit Of Detection ◽  
Differential Pulse ◽  
Electrochemical Analysis ◽  
Molybdenum Oxides ◽  
Modified Glassy Carbon Electrode ◽  
Pharmaceutical Dosage Form ◽  
Maximum Peak ◽  
Peak Separation ◽  
Limit Of Quantitation

Manganese and Molybdenum oxides are well-known electro-catalysts in fuel cells systems; they are usually used as anodic materials for the oxidation of low molecular weight alcohols. The utilization of MoO2 and MnO2 as catalysts in the pharmaceutical analysis is not common yet an analytical method for the determination of Sulfamethoxazole (SMX) antibacterial agents in Pharmaceutical Dosage form is developed. The method is based on the voltammetric determination of SMX using modified glassy carbon electrode by molybdenum oxide. The two components are oxidized at the modified electrode surface with the development of current that is linearly proportional to their concentrations in the range of 7.04*10-7- 1*10-3 M for SMX. The oxidation reaction of the two components is pH-dependent, in which the buffer used is Britton-Robinson at pH = 7.00 where maximum peak current and maximum peak separation is obtained. The regression factors obtained from the calibration curves are 0.9790 for SMX and 0.9812 for TMP. The method of analysis was validated, where the limit of detection (LOD) and the limit of quantitation (LOQ) of SMX were calculated to be 1.44*10-4 M, 4.36*10-4 M and 1.27*10-4 M, 3.84*10-4 M respectively, The percentage recovery of both components was also calculated to 81 % for SMX.

scholarly journals Smartphone-Based Chemiluminescent Origami µPAD for the Rapid Assessment of Glucose Blood Levels

Biosensors ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 381
Author(s):  
Donato Calabria ◽  
Martina Zangheri ◽  
Ilaria Trozzi ◽  
Elisa Lazzarini ◽  
Andrea Pace ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Limit Of Detection ◽  
Point Of Care ◽  
Rapid Assessment ◽  
Blood Levels ◽  
Blood Samples ◽  
3D Printed ◽  
Diagnostic Applications ◽  
Catalyzed Oxidation

Microfluidic paper analytical devices (µPADs) represent one of the most appealing trends in the development of simple and inexpensive analytical systems for diagnostic applications at the point of care (POC). Herein, we describe a smartphone-based origami µPAD for the quantitative determination of glucose in blood samples based on the glucose oxidase-catalyzed oxidation of glucose leading to hydrogen peroxide, which is then detected by means of the luminol/hexacyanoferrate(III) chemiluminescent (CL) system. By exploiting the foldable µPAD format, a two-step analytical procedure has been implemented. First, the diluted blood sample was added, and hydrogen peroxide was accumulated, then the biosensor was folded, and a transport buffer was added to bring hydrogen peroxide in contact with CL reagents, thus promoting the CL reaction. To enable POC applicability, the reagents required for the assay were preloaded in the µPAD so that no chemicals handling was required, and a 3D-printed portable device was developed for measuring the CL emission using the smartphone’s CMOS camera. The µPAD was stable for 30-day storage at room temperature and the assay, displaying a limit of detection of 10 µmol L−1, proved able to identify both hypoglycemic and hyperglycemic blood samples in less than 20 min.

scholarly journals New potentiometric electrode based on ion pair complex for determination of tropicamide in pure and pharmaceutical formulations

2016 ◽  
Vol 6 (4) ◽  
pp. 277 ◽  
Author(s):  
Mouhammed Khateeb ◽  
Basheer Elias ◽  
Hazar Alksair
Keyword(s):  
Limit Of Detection ◽  
Pharmaceutical Formulations ◽  
Graphite Powder ◽  
Fast Response ◽  
Ion Pair ◽  
Modified Carbon Paste Electrode ◽  
Mechanical Resistance ◽  
Carbon Paste ◽  
Electroactive Material

<p class="PaperAbstract"><span lang="EN-US">Construction and general performance of a novel modified carbon paste electrode (MCPE) for determination of tropicamide (TPC) in pure form and pharmaceutical formulations have been examined. Tropicamide-tetraphenylborate (TPC–TPB) ion pair has been prepa­red and used as electroactive material. The best MCPE electrode was composed of 7 % ion-pair, 46.5 % dioctylphthalat and 46.5 % graphite powder. The electrode shows stable potentiometric response for TPC in the concentration range 0.3–221.0 µM at 25 °C and pH range of 2.0–8.0. The electrode exhibits near Nernstian slope of 59.71±0.30 mV/decade and lower limit of detection of 0.09 µM with fast response time (less than 15 s). The selectivity of the electrode (TPC–TPB) was investigated with respect to some organic and inorganic cations. The MCPE was designed to have better mechanical resistance. The proposed method was successfully applied for determination of TPC in eye drop formulation.</span></p>

scholarly journals Method validation in quantitative electrochemical analysis of colchicine using glassy carbon electrode

2007 ◽  
Vol 5 (3) ◽  
pp. 766-778 ◽  
Author(s):  
Ede Bodoki ◽  
Robert Săndulescu ◽  
Liviu Roman
Keyword(s):  
Detection Limit ◽  
Glassy Carbon Electrode ◽  
Glassy Carbon ◽  
Limit Of Detection ◽  
Electrochemical Analysis ◽  
Carbon Electrode ◽  
Cathodic Peak ◽  
Limit Of Quantification ◽  
Validation Parameters

AbstractA cathodic differential pulse voltammetric determination of colchicine was validated using a glassy carbon electrode in HClO4/H3PO4 0.01 M. Colchicine gives an irreversible, diffusion-controlled peak at −862 mV vs. Ag/AgCl reference electrode. The cathodic peak is strongly influenced by a more alkaline environment with a shift towards more negative potentials. Method optimization was carried out in parallel for three types of electrodes (glassy carbon, mercury film and bismuth film coated glassy carbon). The cathodic peak current is higher using film-coated electrodes, but shows poorer intra-day reproducibility and a longer analysis time due to film renewal. Thus, a bare glassy carbon electrode was used to determine colchicine in the concentration range of 2.4 − 50 μg mL−1 (R 2 = 0.9998, n = 5), with a calculated detection limit of 0.80 μg mL−1. The proposed method was characterized according to ICH Harmonized Tripartite Guidance Q2(R1) by validation parameters (selectivity, linearity, accuracy, fidelity, limit of detection, limit of quantification) and it was successfully applied for the determination of colchicine from tablets, without the interference of the excipients. The method’s performances were evaluated and compared with both a known polarographic method and the official quantitative spectrophotometric determination from the Romanian Pharmacopoeia, Xth edition, respectively.

scholarly journals Voltammetric Determination of Uric Acid in Clinical Serum Samples Using DMF Modified Screen Printed Carbon Electrodes

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Melaku Metto ◽  
Samrawit Eramias ◽  
Bekele Gelagay ◽  
Alemayehu P. Washe
Keyword(s):  
Uric Acid ◽  
Limit Of Detection ◽  
Phosphate Buffer Solution ◽  
Clinical Samples ◽  
Carbon Electrodes ◽  
Current Response ◽  
Serum Samples ◽  
Relative Standard ◽  
Screen Printed

Screen printed carbon electrodes (SPCEs) provide attractive opportunity for sensitive and selective determination target analytes in clinical samples. The aim of the current work was to develop SPCEs based sensor for the determination of uric acid in clinical serum samples. The electrodes were pretreated by soaking in N,N-dimethylformamide for 5 minutes followed by drying in an oven at 100°C for 20 mins. The effect of surface pretreatment was characterized using cyclic voltammetry. The current response of uric acid detection was improved by a factor of 3.5 in differential pulse voltammetric measurement compared to unmodified electrode. Under the optimized conditions, the sensor displayed two dynamic linear ranges 5-100 μM and 100-500 μM with correlation coefficient, R2, values of 0.98782 and 0.97876, respectively. The limit of detection and limit of quantification calculated using the dynamic linear range 5-100 μM were 1.9 x 10−7 M and 6.33 x 10−7 M, respectively. The developed sensor displayed well separated and discerned peaks for UA in presence of the potential interferent (ascorbic acid and citric acid). The electrode was successfully applied for the detection of very low level of UA in clinical serum samples in a phosphate buffer solution (pH = 7). The proposed sensor showed a very high reproducibility and repeatability with the relative standard deviation of 0.9%. In conclusion, a simple and low cost sensor based on SPCEs is developed for sensitive and selective detection of uric acid in clinical samples.

scholarly journals Nanostructured TiO2 Carbon Paste Based Sensor for Determination of Methyldopa

2018 ◽  
Vol 11 (4) ◽  
pp. 99
Author(s):  
Luane Ferreira Garcia ◽  
Carlos Eduardo Peixoto da Cunha ◽  
Emily Kussmaul Gonçalves Moreno ◽  
Douglas Vieira Thomaz ◽  
Germán Sanz Lobón ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Low Cost ◽  
Pharmaceutical Formulations ◽  
Graphite Powder ◽  
Differential Pulse ◽  
Carbon Paste ◽  
X Ray Diffraction ◽  
Pharmaceutical Samples ◽  
Nanostructured Tio2

Methyldopa is a catecholamine widely used in the treatment of mild to moderate hypertension whose determination in pharmaceutical formulae is of upmost importance for dose precision. Henceforth, a low-cost carbon paste electrode (CPE) consisting of graphite powder obtained from a crushed pencil stick was herein modified with nanostructured TiO2 (TiO2@CPE) aiming for the detection of methyldopa in pharmaceutical samples. The TiO2-modified graphite powder was characterized by scanning electron microscopy and X-ray diffraction, which demonstrated the oxide nanostructured morphology. Results evidenced that sensitivity was nonetheless increased due to electro-catalytic effects promoted by metal modification, and linear response obtained by differential pulse voltammetry for the determination of methyldopa (pH = 5.0) was between 10–180 μmol/L (Limit of Detection = 1 μmol/L) with the TiO2@CPE sensor. Furthermore, the constructed sensor was successfully applied in the detection of methyldopa in pharmaceutical formulations and excipients promoted no interference, that indicates that the sensor herein developed is a cheap, reliable, and useful strategy to detect methyldopa in pharmaceutical samples, and may also be applicable in determinations of similar compounds.

scholarly journals Screen-Printed Soft-Nitrided Carbon Electrodes for Detection of Hydrogen Peroxide

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3741
Author(s):  
Chidiebere I. Ogbu ◽  
Xu Feng ◽  
Samson N. Dada ◽  
Gregory W. Bishop
Keyword(s):  
Hydrogen Peroxide ◽  
Electrocatalytic Activity ◽  
Carbon Materials ◽  
Limit Of Detection ◽  
Amperometric Detection ◽  
Graphite Powder ◽  
Carbon Electrodes ◽  
Nitrogen Doped ◽  
Nitrogen Doped Carbon ◽  
Screen Printed

Nitrogen-doped carbon materials have garnered much interest due to their electrocatalytic activity towards important reactions such as the reduction of hydrogen peroxide. N-doped carbon materials are typically prepared and deposited on solid conductive supports, which can sometimes involve time-consuming, complex, and/or costly procedures. Here, nitrogen-doped screen-printed carbon electrodes (N-SPCEs) were fabricated directly from a lab-formulated ink composed of graphite that was modified with surface nitrogen groups by a simple soft nitriding technique. N-SPCEs prepared from inexpensive starting materials (graphite powder and urea) demonstrated good electrocatalytic activity towards hydrogen peroxide reduction. Amperometric detection of H2O2 using N-SPCEs with an applied potential of −0.4 V (vs. Ag/AgCl) exhibited good reproducibility and stability as well as a reasonable limit of detection (2.5 µM) and wide linear range (0.020 to 5.3 mM).

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