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The present paper describes the voltammetric analysis of dipyridamole (DIP) at a cheap, disposable pencil graphite electrode (PGE). The working conditions were optimized with regard to the electrode material and the supporting electrolyte. Cyclic voltammetric investigations emphasized that DIP is irreversibly oxidized at the PGE. The electrode process is pH-dependent and controlled by both diffusion and adsorption. For DIP quantitative determination a differential pulse voltammetric (DPV) method in phosphate buffer solution pH 7.00 was developed. DIP's oxidation peak current varied linearly with the analyte concentration, presenting two linear ranges, namely 5.00 x 10-7 -2.50 × 10-5 M and 2.50 × 10-5 -2.50 × 10-4 M, with detection and quantification limits of 1.21 × 10-7 M and 4.03 × 10-7 M DIP, respectively. The newly developed DPV method using the inexpensive, disposable PGE was successfully applied for the simple and rapid determination of DIP from pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

Ferulic acid (FA), a monohydroxycinnamic acid, is an antioxidant with multiple beneficial effects on human health, presenting also importance in the food and cosmetics industry. Its electrochemical behavior was investigated at the disposable and cost-effective pencil graphite electrode (PGE). Cyclic voltammetry emphasized its pH-dependent, diffusion-controlled oxidation. Using the optimized conditions (HB type PGE, Britton Robinson buffer pH 4.56) differential pulse and square-wave voltammetric techniques were applied for its quantitative determination in the range 4.00 × 10−7–1.00 × 10−3 mol/L FA. The developed methods were employed for the rapid and simple assessment of the FA content from a commercially available powder designed for cosmetic use. [ABSTRACT FROM AUTHOR]

For the first time, silver nanoparticles (AgNPs) were fabricated with graphite pencil electrode (GPE) by immersing a bare hard black pencil (HB pencil) in AgNO3 solution mixed with extract Quercus infectoria solution, followed by placing directly against to UV lamp (254 nm) and kept for 30 min. Silver modified-GPEs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDX). The silver nanoparticles fabricated with graphite pencil electrode (AgNPs-GPE) showed excellent selectivity to chloride ion, as well as excellent reproducibility, together with it has several advantages such as sensitivity, simplicity, low cost, green, and fast response. The maximum oxidation cyclic voltammogram current of the AgNPs-PGE was found at 160 mV. The linear range of chloride ions detection is between (0.8-52 mmol L-1), and the limit of detection (LOD) of chloride ions is 0.041 mmol L-1. Finally, the Silver fabrication electrode was used to determine the chloride ion concentration in drugs, such as phenylephrine, metformin, procaine, and dopamine formulated with hydrochloride, and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

Herein, we proposed a cost-effective, eco-friendly, fast and sensitive square wave cathodic stripping voltammetry (SWCSV) and differential pulse cathodic stripping voltammetry (DPCSV) methods for the quantification of anti-ulcer drug cinitapride in pharmaceuticals. Cinitapride electrochemically reduced at pencil graphite electrode and gave an irreversible well-defined cathodic peak in cyclic, square wave, and differential pulse voltammograms. The effect of pH of buffer, scan rates, and drug concentration on peak current and peak potential were studied. The reduction of cinitapride at pencil graphite electrode was diffusion controlled and occurred via participation of two electrons and two protons (2e−/2H+). The various electro-kinetic parameters such as diffusion coefficient(Do), surface coverage (To)and electron transfer coefficient (α) were calculated, additionally, the mechanism of reduction of cinitapride at pencil graphite electrode was also proposed. The peak currents vary linearly in the concentration range 2.48 μmolL−1 to 17.39 μmolL−1 for all the voltammetric techniques. The obtained value of LOD for SWCSV and DPCSV techniques were2.48 μmolL−1 and 3.19 μmolL−1, respectively, which proved higher sensitivity of the proposed methods. [ABSTRACT FROM AUTHOR]

Pencil graphite electrode (PGE) is an alternative, commercially available, ready-to-use, screen-printed electrode for a wide range of electroanalytical applications. Due to the complex-matrix composition and unpredictable electro-inactive nature of PGE in its native form, a surface pre-treatment/activation procedure is highly preferred for using it as an electroactive working electrode for electroanalytical applications. In this article, we review various surface pre-treatment and modification procedures adopted in the literature with respect to the sensitive and selective detection of dopamine as a model system. Specific generation of the carbon–oxygen functional group, along with partial surface exfoliation of PGE, has been referred to as a key step for the activation. Based on the Scopus® index, the literature collection was searched with the keywords "pencil and dopamine". The obtained data were segregated into three main headings as: (i) electrochemically pre-treated PGE; (ii) polymer-modified PGEs; and (iii) metal and metal nanocomposite-modified PGE. This critical review covers various surface activation procedures adopted for the activation for PGE suitable for dopamine electroanalytical application. [ABSTRACT FROM AUTHOR]

The presented study focuses on the optimum conditions for chemical activation of pencil graphite electrodes (PGE) used in the determination of bisphenol A (BPA). The prepared ethanol–HCl mixture for chemical activation of pencil graphite electrode exhibits better activation factor compared with traditional activation methods like anodizing. The obtained porous and highly conductive surface of PGE can be used as a sensing device. The electrochemical behavior of BPA at the modified sensor was investigated. The effects of pH, accumulation time and sensor activation were examined. In the optimum experimental conditions, adsorptive differential pulse voltammetry was used for determination of BPA, which exhibits a linear calibration graph of Ip versus BPA concentration in the range 1.25 × 10–8 to 1.34 × 10–4 M. The calculated detection limit for S/N = 3 was 1.0 nM. The presented sensor is reusable. The activated PGE was applied for the determination of BPA leached from baby bottles as a real sample using spike method. [ABSTRACT FROM AUTHOR]

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This work describes the sensitive voltammetric determination of favipiravir (FAV) based on its reduction for the first time with a low‐cost and disposable pencil graphite electrode (PGE). In addition, the determination of FAV was also performed based on its oxidation. Differential pulse (DP) voltammograms recorded in 0.5 M H2SO4 for the reduction of FAV show that peak currents increase linearly in the range of 1.0 to 600.0 μM with a limit of detection of 0.35 μM. The acceptable recovery values (98.9–106.0 %) obtained from a pharmaceutical tablet, real human urine, and artificial blood serum samples spiked with FAV confirm the high accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

Pencil graphite electrode (PGE) modified with MWCNT and Bi3+ (MWCNT/Bi/PGE) was utilized in simultaneous analysis of Pb2+, Cd2+, and Zn2+. Surface and electrochemical characteristics of MWCNT/Bi/PGE were investigated via SEM, cyclic voltammetry, electrochemical impedance spectroscopy, and FTIR measurements. Even though modification with MWCNT did not improve the electroactive surface area, it significantly decreased the charge transfer resistance. Furthermore, modification with Bi3+ significantly increased the sensitivity. Finally, MWCNT/Bi/PGE exhibited the highest sensitivity and reproducibility compared to PGE and PGE modified with only MWCNT. MWCNT/Bi/PGE provided LOD values of 0.27, 0.43, and 1.63 μg L−1, and linear ranges of 1–80, 5–80, and 10–80 μg L−1 for Pb2+, Cd2+, and Zn2+, respectively. Proposed modification method offers effective electroanalytical performance with low time consumption and cost for the analyst. [ABSTRACT FROM AUTHOR]

A sensitive and inexpensive differential pulse voltammetric technique was applied to investigate the electrochemical behavior of alfuzosin hydrochloride at two different working electrodes: silica gel modified carbon paste and pencil graphite electrodes (PGE). The voltammetric conditions were optimized using cyclic voltammetry, showing an irreversible anodic peak in Britton-Robinson buffered medium (pH 6) at 0.86-0.90 V. The electrochemical responses were linearly correlated with alfuzosin concentrations (R2 > 0.999) in the ranges of 0.6-20 and 0.3-20 µM, exhibiting higher electrocatalytic activity at PGE with a low detection limit/detectability of 0.099 µM. In addition, this study was a successful attempt for the drug determination in tablets and spiked urine samples with green profile evaluation, employing the National Environmental Methods Index, analytical Eco-Scale score, and Green Analytical Procedure Index. [ABSTRACT FROM AUTHOR]

Hesperidin (HESP) is a plant bioflavonoid found in various nutritional and medicinal products. Many of its multiple health benefits rely on the compound's antioxidant ability, which is due to the presence of oxidizable hydroxyl groups in its structure. Therefore, the present study aimed to investigate the electrochemical behavior of HESP at a cheap, disposable pencil graphite electrode (PGE) in order to develop rapid and simple voltammetric methods for its quantification. Cyclic voltammetric investigations emphasized a complex electrochemical behavior of HESP. The influence of the electrode material, solution stability, supporting electrolyte pH, and nature were examined. HESP main irreversible, diffusion-controlled oxidation signal obtained at H type PGE in Britton Robinson buffer pH 1.81 was exploited for the development of a differential pulse voltammetry (DPV) quantitative analysis method. The quasi-reversible, adsorption-controlled reduction peak was used for HESP quantification by differential pulse adsorptive stripping voltammetry (DPAdSV). The linear ranges of DPV and DPAdSV were 1.00 × 10−7–1.20 × 10−5 and 5.00 × 10−8–1.00 × 10−6 mol/L with detection limits of 8.58 × 10−8 and 1.90 × 10−8 mol/L HESP, respectively. The DPV method was applied for the assessment of dietary supplements bioflavonoid content, expressed as mg HESP. [ABSTRACT FROM AUTHOR]

A sensitive differential pulse (DP) voltammetric method has been proposed for the determination of trifluralin (TFA) based on both its reduction and oxidation at a disposable pencil graphite electrode (PGE). DP voltammograms recorded under optimized conditions show that oxidation and reduction peak currents increased linearly in the range from 1.0 to 75.0 μM and from 0.50 to 100.0 μM TFA, respectively. LOD and sensitivity values have been determined as 0.39 μM and 11170 μA mM−1 cm−2 for oxidation and as 0.20 μM and 22167 μA mM−1 cm−2 for reduction. The acceptable recovery values (95.2–104.8 %) were obtained from real water samples. [ABSTRACT FROM AUTHOR]

Simultaneous anodic adsorptive stripping voltammetry was applied for selective and sensitive electrochemical determination of the flavones luteolin (LU) and the basic flavone core 3‐hydroxyflavone (3HF) using a renewable pencil graphite electrode (PGE). The increased separation of the anodic peak potential of LU and 3HF on a PGE surface together with the increased sensitivity renders their simultaneous determination feasible by square wave anodic adsorptive stripping voltammetry (SWAASV). The electrochemical parameters such as surface concentration (Γ), electron transfer coefficient (α), and the standard rate constant (ks) of both LU and 3HF at a PGE were calculated. For simultaneous detection of both compounds by synchronous change of the concentration of LU and 3HF, the detection limits were 1.34 nM and 5.15 nM, respectively. The proposed procedure was successfully applied for the simultaneous detection of LU and 3HF in human serum and urine samples with satisfactory results. [ABSTRACT FROM AUTHOR]

In this study, ZnO nanoflowers (ZnONFs) were synthesized using sonochemical method, which is a simple, environmentally friendly, low-cost and rapid method. ZnONFs was characterized by using FE-SEM, EDS, elemental mapping, FTIR and XRD techniques. Single use pencil graphite electrode (PGE) modified with ZnONFs was characterized using FE-SEM, EDS, elemental mapping, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. This developed electrode was used for the first time for the determination of calf thymus double-stranded DNA (dsDNA) and the chemotherapeutic drug Gemcitabine (GEM) using differential pulse voltammetry (DPV). The detection limits (DLs) of dsDNA and GEM were calculated as 1.91 μg/mL and 2.47 μg/mL, respectively. The interaction of GEM and dsDNA at different times was investigated by measuring the changes in both GEM and guanine oxidation signals by DPV technique. The developed nanoflower-based biosensor responded in as short as 5 min in the DNA-anticancer drug interaction study. The study provides advantages such as low cost, biocompatibility, and easy synthesis of the used nanomaterial synthesis, as well as low detection limit and short interaction time at the sensor stage. [Display omitted] • ZnO nanoflowers modified pencil graphite electrodes (ZnONFs-PGE) were developed. • The electrochemical measurements were performed by DPV, CV and EIS techniques. • The electrochemical monitoring of anticancer drug Gemcitabine and dsDNA interaction was performed. [ABSTRACT FROM AUTHOR]

A novel and label-free electrochemical sensing strategy was explored for designing the ultra-low-level dopamine sensor based on a low-cost pencil graphite electrode (PGE). Electrochemical measurements of the PG electrode towards dopamine detection were performed using the anodic sweeping voltammetry (ASV) technique with optimized deposition voltage and time. With a sensitivity of 0.022 μA nM−1 cm−2, the PG electrode demonstrated sufficient potential for highly selective detection of dopamine down to 26.5 nM concentration in the presence of other interfering bioanalytes. [Display omitted] • Pencil graphite electrode (PGE) shows excellent low-level detection ability of Dopamine. • PGE offers very low-cost sensing strategy for Dopamine sensor. • Bare PGE can detect dopamine down to 26.5 nM. • PGE shows excellent specific selectivity of the Dopamine in the presence of ascorbic and uric acids. • PGE based Dopamine sensor shows 74 % reusibility. [ABSTRACT FROM AUTHOR]

Diosmin (DIO) is a naturally occurring flavonoid with multiple beneficial effects on human health. The presence of different hydroxyl groups in diosmin structure enables its electrochemical investigation and quantification. This work presents, for the first time, diosmin voltammetric behavior and quantification on the cost-effective, disposable pencil graphite electrode (PGE). Diosmin oxidation on PGE involves two irreversible steps, generating products with reversible redox behaviors. All electrode processes are pH-dependent and predominantly adsorption-controlled. Differential pulse (DPV) and adsorptive stripping differential pulse (AdSDPV) voltammetric methods have been optimized for diosmin quantification o an H-type PGE, in 0.100 mol/L H2SO4. The linear ranges and limits of detection were for DPV 1.00 × 10−6–1.00 × 10−5 mol/L and 2.76 × 10−7 mol/L DIO for DPV and 1.00 × 10−7–2.50 × 10−6 mol/L and 7.42 × 10−8 mol/L DIO for AdSDPV, respectively. The DPV method was successfully applied for diosmin quantification in dietary supplement tablets. The percentage recovery was 99.87 ± 4.88%. [ABSTRACT FROM AUTHOR]

• For the first time a combined electrode system (TyB-GGG) was introduced. • Good electrocatalytic performance of TyB-GGG towards the analyte determination. • Present method replaces the reference electrode and also liquid junction potential. • TyB-GGG successfully employed for the analysis of Hydrochlorothiazide (HTZ). A Trypan Blue modified combined pencil graphite electrode system (TyB-GGG) has been employed for the electrochemical investigation of Hydrochlorothiazide (HTZ). The linear calibration curves were obtained in the concentration range of 0.5–7 µM (for DPV) and 0.1–5 µM (for SWV), respectively. The detection limits were found to be 0.1327 µM and 0.0320 µM, respectively. The electrodes resistance has been studied using electrochemical impedance spectroscopy (EIS). The modified electrode TyB-GGG has been successfully employed for the determination of HTZ present in pharmaceutical sample. [ABSTRACT FROM AUTHOR]

A concentric thin layer cell accommodating a non-standard 0.2 mm diameter pencil graphite disposable working electrode is described. The cell was installed into HPLC manifold as an electrochemical detector. Trouble-free operation in mobile phases containing both low and high content of organic solvents is demonstrated by HPLC analyses of phenolic acids and tocopherol isomers. The data obtained from HPLC separation of model mixtures of gentisic, caffeic and dihydrocaffeic acids show a remarkable electrolytic efficiency exceeding 80% at 200, and 50% at 500 μL min−1, while for gentisic acid the limit of detection (LOD) was 0.4 nmol L−1 at 20 microliter sample loading (8 fmol on-column). Similar performances were found in non-aqueous mobile phase, where a LOD of 0.8 nmol L−1 was achieved for delta-tocopherol. The developed flow-through detector is designed to allow easy replacement of pencil graphite working electrode in a highly reproducible manner. The relative standard deviation for the HPLC analysis of tocopherol isomers was of 5.3% (n = 3, C = 500 nmol L−1). The combination of simple construction, excellent electrochemical performance and hydrodynamics identical to that of commercial UV-VIS HPLC detector suggests that the proposed device is a viable low-cost alternative to commercially available electrochemical detectors. [ABSTRACT FROM AUTHOR]