Unmodified Screen-printed Electrodes Research Articles

Electrochemical determination of riboflavin in pharmaceuticals using unmodified screen printed carbon electrodes.

In this study, we have devised an efficient and rapid approach to detect riboflavin (also known as Vitamin B2 or VB2) utilizing an unaltered screen-printed carbon electrode (SPCE). The unmodified screen-printed electrodes are created within the laboratory, where carbon ink is applied to a ceramic substrate. All experiments pertaining to the investigation of electrochemical behavior and the fine-tuning of crucial experimental parameters were conducted through cyclic voltammetry (CV). For quantitative assessments, square wave voltammetry (SWV) was employed. The findings indicate that unaltered SPCEs exhibit robust current signals during the riboflavin redox reaction. Riboflavin displays a distinct oxidation peak at -0.136V (vs. Ag/AgCl, 3.0M KCl) in a Britton-Robinson buffer solution (BRBS) at pH 2, which was employed for quantification. The electrode demonstrates a broad linear range from 0.05 to 10µM, boasting a detection limit of 0.03µM. Repeatability stands at 1.45%, while reproducibility is 6.61%. Testing the influence of common interfering compounds yielded negligible results. The sensor effectively determines riboflavin content in pharmaceutical formulations without any prior treatment. This method presents an economical, modifier-free sensor with exceptional sensitivity and cost-effectiveness, making it suitable for rapid riboflavin quantification.

Synchronous analysis of acetaminophen, codeine, and caffeine in human fluids employing graphite screen-printed electrodes.

A facile electrochemical approach is proposed for the synchronous determination of acetaminophen (ACP), codeine (COD) and caffeine (CAF) utilizing unmodified screen-printed electrodes (SPEs). The determination of ACP, COD and CAF has been explored across different supporting electrolytes including sulfuric acid (H2SO4), hydrochloric acid (HCl), phosphoric acid (H3PO4) and Briton Robinson (B.R) buffer solutions. It was found that a 0.05 mol L-1 sulfuric acid solution is an optimal supporting electrolyte utilized for voltammetric analysis of ACP, COD, and CAF with improved sensitivity, stability, and reproducibility. The electro-analytical sensing of ACP, COD and CAF was investigated using SPEs within linear concentration ranges of 3.0-35.0 μmol L-1, 10-160 μmol L-1 and 10-160 μmol L-1 and revealed competitively low limits of detection (3S/N) of 0.9, 4.8 and 6.3 μmol L-1 for ACP, COD and CAF, respectively. The results indicated the possibility of such a simple and quick electroanalytical protocol for online monitoring of pharmaceutical formulations comprising ACP, COD, and CAF drugs in human fluids with satisfactory recovery.

Boron-doped diamond nanosheet volume-enriched screen-printed carbon electrodes: a platform for electroanalytical and impedimetric biosensor applications

This paper focuses on the development of a novel electrode based on boron-doped diamond nanosheet full-volume-enriched screen-printed carbon electrodes (BDDPE) for use as an impedimetric biosensor. Impedimetric biosensors offer high sensitivity and selectivity for virus detection, but their use as point-of-care devices is limited by the complexity of nanomaterials’ architecture and the receptor immobilisation procedures. The study presents a two-step modification process involving the electroreduction of diazonium salt at the BDDPE and the immobilisation of antibodies using zero-length cross-linkers for a selective impedimetric biosensor of Haemophilus influenzae (Hi). The incorporation of diamond nanosheets into BDDPE leads to enhanced charge transfer and electrochemical behaviour, demonstrating greatly improved electrochemically active surface area compared with unmodified screen-printed electrodes (by 44% and 10% on average for [Ru(NH3)6]Cl2 and K3[Fe(CN)6], respectively). The presented sensing system shows high specificity towards protein D in Hi bacteria, as confirmed by negative controls against potential interference from other pathogens, with an estimated tolerance limit for interference under 12%. The Hi limit of detection by electrochemical impedance spectroscopy was 1 CFU/mL (measured at − 0.13 V vs BDDPE pseudo-reference), which was achieved in under 10 min, including 5 min sample incubation in the presence of the analyte.Graphical abstract

Validated portable device for the qualitative and quantitative electrochemical detection of MDMA ready for on-site use

Identifying and quantifying 3,4-methyl​enedioxy​methamphetamine (MDMA) on-site in suspected illicit drug samples, whether it be at recreational settings or manufacturing sites, is a major challenge for law enforcement agencies (LEAs). Various analytical techniques exist to fulfil this goal, e.g. colourimetry and portable spectroscopic techniques, each having its specific limitations (e.g. low accuracy, fluorescence, no quantification) and strengths (e.g. fast, easy to use). In this work, for the first time, an electrochemical MDMA sensor is presented to become a detection tool that can realistically be used on-site. More specifically, the use of a single buffer solution and an unmodified screen-printed electrode, along with the integration of a data analysis algorithm and mobile application permits the straightforward on-site identification and quantification of MDMA in suspicious samples. Multiple studies investigating different parameters, including pH, concentration, reproducibility, temperature and binary mixture analyses, were executed. To fully understand all the occurring redox processes, liquid chromatography coupled with high-resolution mass spectrometry analysis of partially electrolyzed MDMA samples was performed unravelling oxidation of the methylenedioxy group. Validation of the methodology was executed on 15 MDMA street samples analysed by gas chromatography coupled with mass spectrometry and compared with the performance of a commercial portable Raman and Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) device. The novel methodology outperformed the spectroscopic techniques, correctly identifying all 15 street samples. Additionally, the electrochemical sensor predicted the purity of the tablets with a mean absolute error of 2.3%. Overall, this new, electrochemical detection strategy provides LEAs the rapid, low-cost, on-site detection and quantification of MDMA in suspicious samples, without requiring specialized training.

Simultaneous detection of dopamine and ascorbic acid by using a thread-based microfluidic device and multiple pulse amperometry.

This study presents a novel approach for the simultaneous detection of ascorbic acid (AA) and dopamine (DA) using an affordable and user-friendly microfluidic device. Microfluidic devices, when combined with electrochemical detectors like screen-printed electrodes (SPEs), offer numerous advantages such as portability, high sample throughput, and low reagent consumption. In this study, a 3D-printed microfluidic device called a μTED was developed, utilizing textile threads as microfluidic channels and an unmodified SPE as the amperometric detector. The method employed multiple pulse amperometry (MPA) with carefully selected potential values (+0.65 V and -0.10 V). The reduction current signals generated by dopamine o-quinone were used to calculate a correction factor for the oxidation signals of ascorbic acid, enabling simultaneous quantification. The developed microfluidic device ensured a stable flow rate of the carrier solution at 1.19 μL s-1, minimizing the consumption of samples and reagents (injection volume of 2.0 μL). Under the optimized experimental conditions, a linear range from 50 to 900 μmol L-1 was achieved for both DA and AA. The obtained sensitivities were 2.24 μA L mmol-1 for AA and 5.09 μA L mmol-1 for DA, with corresponding limits of detection (LOD) of 2.60 μmol L-1 and 1.54 μmol L-1, respectively. To confirm the effectiveness of the proposed method, it was successfully applied to analyze AA and DA in a commercial blood serum sample spiked at three different concentration levels, with a medium recovery rate of 70%. Furthermore, the MPA technique demonstrated its simplicity by enabling the simultaneous determination of AA and DA without the need for prior separation steps or the use of chemically modified electrodes.

Promoting Electron Transfer Kinetics and Adsorption Capacity for the Detection of Furazolidone in Real Food Samples by Using Ag-core@Fe3O4-Shell-Based Electrochemical Sensing Platform

In this study, the preparation of core/shell Ag@Fe3O4 nanoparticles (NPs) and its potential application toward highly sensitive electrochemical detection of furazolidone (FZD) have been reported. UV–visible spectroscopy, X-ray diffraction, scanning electron microscopy, and Zeta sizer are systematically carried out to confirm the formation, size distribution, and composition of Ag@Fe3O4 NPs. By computing the electrochemical characteristic parameters such as electrochemically active surface area (ECSA), electron-transfer resistance (Rct), standard heterogeneous rate constant (k0), adsorption capacity (Γ), and electron transfer rate constant (ks), the Ag@Fe3O4-modified electrode possessed remarkably enhanced electrochemical sensing performance for FZD determination compared to the unmodified screen-printed electrode (SPE). This enhancement of electrochemical activity can be attributed to the fast electron transfer kinetics and great adsorption capacity that arise from the synergistic coupling between the good electrical conductivity of the core AgNPs and the porosity of the protective Fe3O4 shell. Under optimum conditions, the Ag@Fe3O4-based electrochemical nanosensor exhibited not only high sensitivity toward FZD detection of 1.36 μA μM−1 cm−2 in the linear ranges from 0.5–15 μM and 15–100 μM, and low detection limit of 0.24 μM but also long-term stability, repeatability, and anti-interference ability. The applicability of the proposed sensing platform in honey and milk samples was also investigated.

Electrochemical Metallization Process on Screen-Printed Electrode for Creatinine Monitoring Application

The formation and dissolution of the conductive paths in an electrochemical metallization (ECM) system is greatly influenced by the mobility of metal ions in the electrolyte, which can be utilized for the sensor application. Here, we report a demonstration of the ECM on the commercially available screen-printed electrode (SPE) strip, which is then utilized for monitoring the concentration of creatinine in an aqueous mixture. Prior to that, the working electrode was modified by drop casting an organic pentamer, 1,4-bis[2-(5-thiophene-2-yl)-1-benzothiopene]-2,5-dioctyloxybenzene (BOBzBT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The electrostatic interaction between the BOBzBT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> radical cations and the creatinine molecules causes the resistance change in the electrochemical cell, influencing the variation of the ECM-induced pinched hysteresis loop. Consequently, the changes were recorded and the calibration curve was obtained. Compared to the unmodified SPE, the BOBzBT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -modified SPE demonstrated good performance in monitoring the concentration of creatinine. The sensor demonstrated 60 s response time with a sensitivity of 8.18 A dL g <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> for a linear detection range of 0.7–1.1 mg/dL. The selectivity and reproducibility of the modified sensor was also demonstrated. The setup’s simple fabrication procedures could open the way for the development of an ECM-based SPE sensor for creatinine monitoring.

Application of a Screen-Printed Carbon Electrode Modified with Printex 6L and Deep Eutectic Solvent for Detection and Quantification of 17β-estradiol

This work proposes the development of a screen-printed electrode (SPE) modified with a mixture of Printex 6L carbon and deep eutectic solvent (DES) (SPE-P6LCDES), used for detection of 17β-estradiol (E2) in mineral water, synthetic urine, and artificial saliva. The characterization of SPE was evaluated by Scanning Electron Microscopy, Fourier Transform Infrared and Electrochemical Impedance Spectroscopy. Electrochemical studies for E2 detection were performed in 0.1 mol L−1 phosphate buffer solution at pH 7.0. The linear range of E2 concentration was 0.00732–0.417 μmol L−1 to unmodified SPE and 0.00090–0.21 μmol L−1 to SPE-P6LCDES, with LOD of 0.177 μmol L−1 and 0.0065 μmol L−1, respectively. The use of DES + Printex 6L carbon as a modifier allowed strong intramolecular interactions between DES and the E2 molecule, increasing the intensity of the current response, since it showed high sensibility, sensitivity and reproducibility. The results obtained to E2 recovery on samples were between 92.15% and 102.10%. The validation study (UV–vis spectroscopy) demonstrated recovery of +99.16% (+1.4%) and +100.16% (+1.9%) to 10 and 60 μmol L−1 E2, respectively.

A sensitive Cu(salophen) modified screen-printed electrode for simultaneous determination of dopamine and uric acid

T&#x0D; This research applied a nanostructured electrochemical sensor with a screen-printed electrode (SPE) for examining the dopamine (DA) electrocatalytic oxidation when uric acid (UA) was present. Cu(salophen) nanostructured modified SPE Cu(salophen)/SPE was employed to investigate the electrochemical behavior of DA. At optimal pH (pH 7.0), oxidation of DA at the modified electrode takes place at a potential around 100 mV less positive than at the unmodified SPE. Chronoamperometry was used to determine the diffusion coefficient of DA (D = 1.96×10-5 cm2 s-1). Differential pulse voltammetry (DPV) showed linear response in the range between 0.2-450.0 μM for DA. The limit of detection (LOD) of DA was computed to be 0.05 μM. Moreover, Cu(salophen)/SPE was employed for determining DA in the presence of UA using DPV. The DPV results showed that at the modified electrode, two well-separated oxidation peaks of DA and UA could be obtained at potentials of 180 and 325 mV, respectively. This separation forms the basis for the co-detection of these two materials on the surface of Cu(salophen)/SPE. This sensor was then employed to determine DA and UA in real specimens.

Electrochemical identification of hazardous phenols and their complex mixtures in real samples using unmodified screen-printed electrodes

The electrochemical behavior of some of the most relevant endocrine-disrupting phenols using unmodified carbon screen-printed electrodes (SPEs) is described for the first time. Experiments were made to assess the electrochemical behavior of phenol (PHOH), pentachlorophenol (PCP), 4-tert octylphenol (OP) and bisphenol A (BPA) and their determination in the most favorable conditions, using voltammetric methods such as cyclic voltammetry (CV), linear sweep voltammetry (LSV) and square wave voltammetry (SWV) in Britton Robinson (BR) buffer. Further, the usefulness of the electrochemical approach was validated with real samples from a local river and was compared to commercial phenols test kit, which is commonly used for on-site screening in industrial streams and wastewaters. Finally, the approach was compared with a lab-bench standard method using real samples, i.e., high-performance liquid chromatography with a photodiode array detector (HPLC-DAD).

Trans-resveratrol electrochemical detection using portable device based on unmodified screen-printed electrode

Trans-resveratrol (t-RESV) is an important and natural polyphenolic antioxidant generally found in grapes and in its derivatives such as red wine and grape juices. The t-RESV has been explored in the pharmaceutical industry for its anti-inflammatory, anti-cancer, and neuroprotective properties. The t-RESV electrochemical determination has basically been carried out using modified electrodes-based sensors. Although these devices show good analytical performance, the electrode preparation can be laborious, and the devices may lack reproducibility. In this sense, it was proposed here a new methodology for the t-RESV electrochemical detection using unmodified screen-printed electrodes and differential pulse voltammetry (DPV). The response of the anodic signal has optimized varying the most important parameters of DPV (pulse time, pulse potential, and pulse step) using the response surface methodology. We showed based on analysis of variance that the new mathematical model developed can predict responses for the t-RESV using DPV. Furthermore, the new analytical method was validated from the limits of detection and quantification. We have still shown that t-RESV can be quantified in commercial drug using DPV with the optimized parameters. The selectivity test also showed that the sensor can be used to determine the antioxidant in other more complex matrices. Additionally, the proposed electrochemical system is completely portable and can work with its own energy, which facilitates point-of-care analysis.

Enhanced electrochemical detection of illicit drugs in oral fluid by the use of surfactant-mediated solution

Illicit drug consumption is a worldwide worrying phenomenon that troubles modern society. For this reason, law enforcement agencies (LEAs) are placing tremendous efforts into tackling the spreading of such substances among our community. New sensing technologies can facilitate the LEAs duties by providing portable and affordable analytical devices. Herein, we present for the first time a sensitive and low-cost electrochemical method, i.e. square-wave adsorptive stripping voltammetry on carbon screen-printed electrodes (SPE), for the detection of five illicit drugs (i.e. cocaine, heroin, 3,4-methylenedioxymethamphetamine, 4-chloro-alpha-pyrrolidinovalerophenone, and ketamine) in oral fluid by the aid of a surfactant. Particularly, the surfactant is adsorbed at the carbon electrode’s surface and yields the adsorption of illicit drug molecules, allowing for an enhanced electrochemical signal in comparison to surfactant-free media. First, the surfactant-mediated behavior is deeply explored at the SPE by cyclic voltammetry, electrochemical impedance spectroscopy, and Fourier-transform infrared spectroscopy. Subsequently, the electrochemical behavior of the five illicit drugs is studied and optimized to render optimal analytical performance. Accordingly, the analytical system exhibited a wide linear concentration range from 1 to 30 µM with sub-micromolar limits of detection and high sensitivity. This performance is similar to other reported electrochemical sensors, but with the advantage of using an unmodified SPE, thus avoiding costly and complex functionalization of the SPE. Finally, the methodology was evaluated in diluted oral fluid samples spiked with illicit drugs. Overall, this work describes a simple, rapid, portable, and sensitive method for the detection of illicit drugs aiming to provide oral fluid testing opportunities to LEAs.

Innovative electrochemical sensor for the precise determination of the new antiviral COVID-19 treatment Favipiravir in the presence of coadministered drugs.

Due the current pandemic of COVID-19, an urgent need is required for serious medical treatments of a huge number of patients. The world health organization (WHO) approved Favipiravir (FAV) as a medication for patients infected with corona virus. In the current study, we report the first simple electrochemical, greatly sensitive sensor using MnO2-rGO nanocomposite for the accurate determination of Favipiravir (FAV). The developed sensor showed a high improvement in the electrochemical oxidation of FAV comparing to the unmodified screen-printed electrode (SPE). The suggested platform constituents and the electrochemical measurements parameters were studied. Under optimal experimental parameters, a current response to the concentration change of FAV was found to be in the linear range of 1.0 × 10-8-5.5 × 10-5 M at pH 7.0 with a limit of detection 0.11 µM and a quantification limit of 0.33 µM. The developed platform was confirmed by the precise analysis of FAV in real samples including dosage form and plasma. The developed platform can be applied in different fields of industry quality control and clinical analysis laboratories for the FAV determination.

Pb(II) Determination in a Single Drop Using a Modified Screen-Printed Electrode

This work presents the development and validation of an electroanalytical method for Pb(II) determination in a single drop. The electrochemical sensors used were an unmodified screen-printed electrode (SPE) and a Bi-film SPE (BiFSPE). Anodic square wave stripping voltammetry (SWASV) was performed at an accumulation potential of −1.5 V vs. Ag/AgCl and an accumulation time of 60 s. Electroanalysis with an unmodified SPE did not yield satisfactory results, whereas the BiFSPE was a much better analysis method. The linear concentration using the BiFSPE was in the range of 138.8–162.5 µg/L. The accuracy and precision were evaluated for different spiked concentrations, but the method using the unmodified SPE was neither accurate nor precise. Using the BiFSPE, the method was found to be both accurate and precise for Pb(II) determination at a concentration of 140.0 μg/L, with recovery and relative standard deviation (RSD) of 106.6% and 12.1%, respectively. In addition, using the BiFSPE, LOD and LOQ values of 1.2 μg/L and 3.3 μg/L were obtained, respectively. The possible interference effect on Pb(II) stripping signal was checked in the presence of Cd(II), Zn(II), Cu(II), Sn(IV), Sb(III), Hg(II), Fe(III), As(V), K(I), I−, Ca(II), and NO3−. Electrochemical impedance spectroscopy measurements were also performed for the unmodified SPE and BiFSPE. The application of single drop Pb(II) analysis was tested by real water sample analysis.

Aptamer-functionalised magnetic particles for highly selective detection of urinary albumin in clinical samples of diabetic nephropathy and other kidney tract disease

We report a new highly selective detection platform for human albumin (HA) in urine based on aptamer-functionalised magnetic particles. Magnetic separation and re-dispersion was utilised to expose the HA-bound particles to a methylene blue solution. A second magnetic collection step was then used to allow the methylene blue supernatant to be reduced at an unmodified screen-printed electrode. Since methylene blue adsorbs to HA, the reduction current fell in proportion to HA concentration. There was no interference from compounds such as dopamine, epinephrine, vanillylmandelic acid, normetanephrine, metanephrine and creatinine in artificial urine at the concentrations at which they would be expected to appear. A calibration equation was derived to allow for the effect of pH on the response. This enabled measurement to be made directly in clinical urine samples of varying pH. After optimisation of experimental parameters, the total assay time was 40 min and the limit of detection was between 0.93 and 1.16 μg mL−1, depending on the pH used. HA could be detected up to 400 μg mL−1, covering the range from normoalbuminuria to macroalbuminuria. Analysis of urine samples of patients, with diabatic nephropathy, type I & II diabetes mellitus and chronic kidney disease, from a local hospital showed good agreement with the standard urinary human albumin detection method.

Application of a Screen-Printed Carbon Electrode Modified with Printex 6L and Deep Eutectic Solvent for Detection and Quantification of 17β-Estradiol

This work proposes the development of a screen-printed electrode (SPE) based on graphite ink as carbonaceous material and modified with a mixture of Printex 6L carbon and deep eutectic solvent (DES) (SPE-P6LCDES), used for detection and quantification of 17β-estradiol (E2) in mineral water, synthetic urine, and artificial saliva samples. The characterization of all electrodes was evaluated by Scanning Electron Microscopy (SEM), Fourier transform infrared (FTIR) and Electrochemical Impedance Spectroscopy (EIS). Electrochemical measurements were performed in a system composed of a single compartment cell (100.0 mL), containing a reference electrode (Ag/AgCl/KClsat), Pt wire as a counter electrode and SPE as a working electrode. Electrochemical studies of E2 were performed in 0.1 mol L-1 phosphate buffer solution (PBS) at pH 7.0 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These studies evaluate the electroactivity of SPE-P6LCDES for E2, showing oxidative signals close to +0.98 V. The linear ranges of E2 concentrations studied were 0.00732 – 0.417 μmol L -1 for unmodified SPE and 0.00090 – 0.21 μmol L-1 for the SPE-P6LCDES, presenting limit of detection (LOD) of 0.177 μmol L-1 and 0.0065 μmol L -1, respectively. The use of DES + Printex 6L carbon as a modifier in the unmodified SPE allowed for strong intramolecular interactions between DES and the E2 molecule, which increased the intensity of the current responses because it is a sensor with greater sensibility, sensitivity, and reproducibility. The results obtained from the E2 recovery study on real samples were between 92.15% and 102.10%. By the method validation study (UV-Vis spectroscopy), the studied E2 concentrations of 10 and 60 μmol L-1 demonstrated recovery of +99.16% (+ 1.4%) and +100.16% (+1.9%), respectively.

Fundamentals and Applications of Electrochemical Impedance Spectroscopy - A Didactic Perspective

Two experiments are presented to introduce students to the utility of electrochemical impedance spectroscopy (EIS) in finding electrodes suitable for applications such as battery development. We used different metal and carbon nanotube (CNT) screen-printed electrodes (SPEs) and compared EIS with cyclic voltammetry (CV) curves. In addition, we prepared the SPEs with graphene powder to show the different behaviour of modified and unmodified SPEs with CV and EIS.

Fabrication of a sensitive electrochemical sensor based on modified screen printed electrode for hydrazine analysis in water samples

ABSTRACT One of the new electrochemical sensors to detect (N2H4) has been constructed on the basis of the screen printed electrode (SPE) modified with poly(vinyl alcohol)/chitosan/TiO2/chlorophyll nanocomposite VA/Chi/TiO2/Chlo/SPE). Therefore, PVA/Chi/TiO2/Chlo nanocomposite has been procured and numerous procedures like energy-dispersive X-ray (EDS), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM) as well as X-ray diffraction (XRD) have been utilised for examining the nanocomposite structure and morphology. In comparison with the unmodified SPE, PVA/Chi/TiO2/Chlo/SPE could notably ameliorate electrooxidation of N2H4 via declining oxidation overpotential and augmenting the oxidation peak current. Moreover, differential pulse voltammetry (DPV) has been employed for quantitatively analysing N2H4. In addition, anodic peak current has been linear to N2H4 concentration in range between 0.045 and 350.0 µM with the limit of detection (LOD) 0.015 µM. In addition, acceptable stability, reproducibility, and sensitivity of the modified electrode have been observed. Furthermore, results indicated functionality of the sensor has been reliable to determine N2H4 in various water samples.

Simultaneous voltammetric determination of two binary mixtures containing propranolol in pharmaceutical tablets and urine samples

Simultaneous voltammetric analysis of two antihypertensive binary mixtures containing propranolol (PROP) in combination with either hydrochlorothiazide (HCTZ) or amlodipine (AML) drugs were investigated for the first time. Disposable screen-printed electrodes (SPEs) were utilized in 0.1 M sulphuric acid and Britton Robinson (B. R.) buffer of pH 7.0 containing 0.28 M sodium dodecyl sulfate (SDS) for analysis of PROP-HCTZ and PROP-AML mixtures, respectively. It was found that assemblage of negatively charged SDS molecules at the graphitic SPE surface significantly enhances the peak height and potential separation to be 0.26 V and 0.32 V (vs. Ag/AgCl) for PROP-HCTZ and PROP-AML, respectively. Under the optimized conditions of differential pulse voltammetry (DPV), the unmodified SPE offered a promising, sensitive, robust electrochemical platform in presence of SDS for the simultaneous determination of PROP mixtures without any interference of their voltammetric signals over wide concentration ranges with nanomolar detection limits. Further, the applicability of suggested method was elucidated in the simultaneous assessment of these antihypertensive drug mixtures in pharmaceutical tablets and urine samples with good recoveries.

Quick and Cost-Effective Estimation of Vitamin C in Multifruit Juices using Voltammetric Methods.

Ascorbic Acid (AA) is a natural and powerful water-soluble antioxidant associated with long-lasting food products. As time passes, the AA content in products sharply decreases, and they become increasingly degraded. There are several techniques to precisely quantify AA concentrations. However, most of them employ costly laboratory instruments, such as High-Performance Liquid Chromatography (HPLC) or complex electrochemical methods, which make unfeasible recurrent AA measurements along the entire supply chain. To address this issue, we contribute with an in-field and real-time voltammetric method, carried out with a low-cost, easy-to-use, and portable device. An unmodified Screen-Printed Electrode (SPE) is used together with the device to achieve short reading times. Our method has been extensively tested in two multifruit juices using three different SPEs. Calibration curves and Limit of Detection were derived for each SPE. Furthermore, periodic experiments were conducted to study the shelf life of juices under consideration. During the analysis, a set of assays for each SPE were implemented to determine the remaining AA amount per juice and compare it with that obtained using HPLC under the same conditions. Results revealed that our cost-effective device is fully comparable to the HPLC equipment, as long as the juice does not include certain interferents; a scenario also contemplated in this article.