Pretreated Pencil Graphite Electrode Research Articles

Facile Electrochemical Sensor for Sensitive and Selective Determination of Guaifenesin, Phenylephrine and Paracetamol on Electrochemically Pretreated Pencil Graphite Electrode.

Guaifenesin (GFS), phenylephrine (PHE) and paracetamol (PAR), drugs used in combination for the relief of cold and flu symptoms, were determined at electrochemically pretreated pencil graphite electrode. Differential pulse voltammetry (DPV) was used for the first time for the concomitant determination of the target compounds based on the electro-oxidation of PAR at 0.43 V, PHE at 0.74 V and GFS at 1.14 V in Britton–Robinson buffer pH 6.0. Under optimized experimental conditions, two linear ranges were obtained for PAR (2.50 × 10−6 M–1.00 × 10−5 M and 1.00 × 10−5 M–1.00 × 10−4 M) and for PHE and GFS linearity was proved between 5.00 × 10−6 M–2.00 × 10−4 M and 2.50 × 10−6 M–2.00 × 10−4 M, respectively. The detection limits were 8.12 × 10−7 M for PAR, 1.80 × 10−6 M for PHE and 8.29 × 10−7 M for GFS. The selective and sensitive DPV method and the electrochemically treated electrode were employed for simultaneous analysis of the analytes in pharmaceutical samples with good recoveries.

Low cost, trouble-free disposable pencil graphite electrode sensor for the simultaneous detection of hydroquinone and catechol

This work proposes, one of the simplest methods for the modification of pencil graphite electrode (PGE) using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. The electrochemical modification (pre-treatment) of the PGE was carried out in 0.1 M NaOH using CV technique by applying a potential in between −0.4 V and 1.4 V. In the presence of phosphate buffer (scan rate-50 mV s-1, 0.2 M, pH ∼ 7.4), the active surface of the pre-treated pencil graphite electrode exhibits improved sensing properties towards the determination of catechol (CC) and hydroquinone (HQ) with improved sensitivity and reproducibility. Sensing characteristics were evaluated under various experimental conditions (scan rate, analyte concentration, interference study & pH variation) for HQ and CC using pre-treated pencil graphite electrode (PPGE). Scan rate dependent sensing study shows that the electrode process is diffusion-controlled at the modified electrode. The pre-treated pencil graphite electrode showed the lower detection limits for HQ and CC is 0.85 μM & 0.59 μM respectively with a wide linear range (HQ: 0.4 to 1.2 × 10−4 M, CC: 0.1 × 10−4 M to 0.7 × 10−4 M). Experimented pre-treated pencil graphite electrode was used and tested for the water from house hold tap which also showed high sensitivity towards HQ and CC.

Development of a voltammetric method for the determination of rapamycin in pharmaceutical samples at pretreated pencil graphite electrode

AbstractThis paper describes an electroanalytical method for the determination of rapamycin using a pretreated pencil graphite electrode (P‐PGE) by differential pulse voltammetry. The electrodes were successfully characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, and Fourier transform infrared. The influences of instrumental and chemical parameters were investigated and optimized for the determination of rapamycin. Oxidation peak current obtained for rapamycin at P‐PGE was 10.5 times higher than that obtained for PGE. In pH = 3.0 H3PO4, a well‐defined irreversible anodic peak occurred at 1.07 V, which was attributed to the electro‐oxidation of rapamycin at P‐PGE. Under optimized conditions, the oxidation peak current of rapamycin was linear with its concentration in the range of 0.01–250 μmol/L, and the detection limit was 0.0075 μmol/L (S/N = 3). Also, the P‐PGE exhibited good reproducibility (relative SD [RSD] = 2.17% for 10 electrodes at different times using the same procedure), repeatability (RSD = 2.09% for 10 measurements with same electrode), and stability (95.80% for 10 days). The P‐PGE was simple to prepare and the method was successfully applied for the determination of rapamycin in spiked and real samples. In addition, for comparison, high‐performance liquid chromatographic method with ultraviolet (UV) detector was used for the determination of rapamycin.

Electroanalytical determination of Allura Red in beverage samples using an anodically pretreated graphite electrode

ABSTRACT In this study, an anodically pretreated pencil graphite electrode (Ptre/PGE) which has oxygen-containing groups was used for the electrochemical determination of Allura Red (AR) by differential pulse voltammetry (DPV) method for the first time in the literature. In order to be more selective and sensitive the pencil graphite electrode, the anodic pretreatment process was performed by applying a constant +1.8 V potential for 250 s in pH 9 phosphate buffer solution using chronoamperometry method. The characterisation studies of the sensor were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) methods. Interference effects of sunset yellow, tartrazine, amaranth, aspartame, glucose, gelatin, and ascorbic acid on AR determination with Ptre/PGE were investigated. The limit of detection and quantitation values was found as 75 and 251 nmol L−1, respectively. The Ptre/PGE has been used for the determination of AR in cherry juice and energy drink samples, where it provides recovery ranging from 98.40% to 100.8%.

Application of Single‐use Electrode Based on Nano‐clay and MWCNT for Simultaneous Determination of Acetaminophen, Ascorbic Acid and Acetylsalicylic Acid in Pharmaceutical Dosage

AbstractIn this study, a highly sensitive, selective and cost‐effective electrochemical nano‐sensor has been developed for the first time so as to facilitate the simultaneous and low‐level detection of acetaminophen (paracetamol, PAR), ascorbic acid (A) and acetylsalicylic acid (ASA) ternary mixture. The sensor is based on nano‐sepiolite clay (SEP) with multiwall carbon nanotubes (MWCNTs) onto electrochemically pretreated pencil graphite electrode (pPGE). The surface properties of the sensor were examined by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. The pH effect, composition of modifiers, immobilization time, deposition potential and deposition time values were optimized to reach the best response of PAR, A and ASA. Moreover, in optimum analytical conditions, adsorptive stripping differential pulse voltammmetric (AdsDPV) method was developed for the simultaneous analysis of the ternary mixtures concerned by using SEP/MWCNTs/pPGE sensor. This sensor exhibited the low detection limits of 0.018, 0.042 and 0.047 μM for PAR, A and ASA ternary mixture, respectively. The developed AdsDPV method was applied for quantitative determination of PAR, A and ASA in the pharmaceutical formulation. The recovery experiments were carried out to control the accuracy and precision of the method. The obtained voltammetric recoveries were comparable with the HPLC data given in the literature.

Electrochemical fabrication of reusable pencil graphite electrodes for highly sensitive, selective and simultaneous determination of hydroquinone and catechol

In the present study, we here report a simple, cost-effective and highly sensitive electrochemical sensor for the selective determination of hydroquinone (HQ) and catechol (CC) using electrochemically pretreated pencil graphite electrode (PPGE). The electrochemical pretreatment of pencil graphite electrode (PGE) was done in phosphate buffer solutions (PBS) and characterized by FT-IR, XRD, SEM and EDX. FT-IR and EDX analysis shows the introduction of oxygen functionalization on the PPGE surface. Further the electrodes were electrochemically characterized using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 0.1M KCl containing K4[Fe(CN)6] as redox probe. Interestingly, The PPGE shows a significant enhancement in the redox peak current of Fe2+/3+, owing to the effective increment in the electroactive surface area at PPGE (1.22cm2) compared with the PGE (0.29cm2). Then the PPGE was utilized for the electrochemical determination of HQ and CC in 0.1M PBS (pH7.0). A reversible electrochemical redox peak for HQ and CC were occurred at PPGE, while PGE doesn't efficiently catalyze the HQ and CC redox reaction under identical experimental conditions. The oxidation current response of HQ and CC at PPGE were increased three and four times respectively compared with the PGE. Further, the DPV analysis displays a wide range of linear responses from 2 to 200μM with a limit of detection (LOD) of 1.17μM for HQ and 1.32μM for CC (S/N=3), respectively. Consequently, the concentration of HQ and CC were successfully determined in the presence of major interferents (10 folds) such as, glucose, ascorbic acid and uric acid. The practical utilization of as-fabricated PPGE was tested in water samples; the obtained results demonstrated that PPGE can be used as a potential candidate for environmental sensor application.

Electrochemical behavior study of some selected phenylurea herbicides at activated pencil graphite electrode. Electrooxidation of linuron and monolinuron

A novel and rapid voltammetric assay for the simultaneous determination of monolinuron (MLN) and linuron (LIN) using an electrochemically pretreated pencil graphite electrode (PGE*) is reported for the first time. Enhanced oxidation peak currents of MLN and LIN were observed at PGE* when compared with electrochemically non-pretreated PGE. Differential pulse voltammetric (DPV) results showed distinct anodic peaks at 1.064 V and 1.170 V for MLN and LIN, respectively. Under optimum conditions, the detection limits were 3.7 × 10−7 mol L−1 and 5.8 × 10−7 mol L−1 for MLN and LIN respectively. The DPV method was applied for the quantitative determination of the mentioned compounds in spiked tap water samples enriched by solid phase extraction. The voltammetric results were in good agreement with high-performance liquid chromatography data.

Sensitive and Rapid Flow Injection Amperometric Hydrazine Sensor using an Electrodeposited Gold Nanoparticle Graphite Pencil Electrode

A gold (Au) nanoparticle-modified graphite pencil electrode was prepared by an electrodeposition procedure for the sensitive and rapid flow injection amperometric determination of hydrazine (N2H4). The electrodeposited Au nanoparticles on the pretreated graphite pencil electrode surface were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and electrochemical impedance spectroscopy. Cyclic voltammograms showed that the Au nanoparticle-modified pretreated graphite pencil electrode exhibits excellent electrocatalytic activity toward oxidation of hydrazine because the highly irreversibly and broadly observed oxidation peak at +600 mV at the pretreated graphite pencil electrode shifted to −167 mV at the Au nanoparticle pretreated graphite pencil electrode; in addition, a significant enhancement in the oxidation peak current was obtained. Thus, the flow-injection (FI) amperometric hydrazine sensor was constructed based on its electrocatalytic oxidation at the Au nanoparticle-modified pretreated graphite pencil electrode. The Au nanoparticle-modified pretreated graphite pencil electrode exhibits a linear calibration curve between the flow injection amperometric current and hydrazine concentration within the concentration range from 0.01 to 100 µM with a detection limit of 0.002 µM. The flow injection amperometric sensor has been successfully used for the determination of N2H4 in water samples with good accuracy and precision.

Simple Real-time Voltammetric Method for Captopril Determination in Pharmaceutical Formulation

A novel voltammetric assay for captopril (CAP) determination by using an electrochemically pretreated pencil graphite electrode (PGE*) is presented. The electrochemical oxidation reaction of CAP was investigated with PGE* by using cyclic voltammetry and linear sweep voltammetry techniques. CAP was electrochemically inactive at the non-pretreated pencil graphite electrode surface, while a sharp anodic wave with an anodic peak potential at around 200 mV resulted by using the PGE*. According to kinetic studies upon the electrode behavior, a new reaction mechanism for electrochemical oxidation of captopril is proposed. The sensor was examined as a selective, simple and precise new electrochemical disposable electrode for the determination of CAP in pharmaceutical samples in complex medical cases associated with sleep apnea, with good results.

Sensitive Flow-Injection Electrochemical Determination of Hydrogen Peroxide at a Palladium Nanoparticle-Modified Pencil Graphite Electrode

A novel flow-injection amperometric method was proposed for the sensitive and enzymeless determination of hydrogen peroxide based on its electrocatalytic reduction at a palladium nanoparticle-modified pretreated pencil graphite electrode in a laboratory-constructed electrochemical flow cell. Cyclic voltammograms of the unmodified and modified electrodes were recorded in pH 7.0 phosphate buffer containing 0.10 M KCl at a scan rate of 50 mV s−1 for the investigation of electrocatalytic reduction of hydrogen peroxide at the palladium nanoparticle-modified pretreated pencil graphite electrode. Cyclic voltammograms of the pretreated pencil graphite electrode revealed an irreversible oxidation peak and a weak reduction peak of hydrogen peroxide at +1100 mV and –450 mV vs. an Ag/AgCl/KCl saturated reference electrode. However, the reduction of hydrogen peroxide was observed at –100 mV with an increase in current in the cyclic voltammograms of the palladium nanoparticle-modified pretreated pencil graphite electrode compared to the unmodified electrode. These results indicate that the palladium nanoparticle-modified pretreated pencil graphite electrode exhibits efficient electrocatalytic activity for the reduction of hydrogen peroxide. A linear concentration range was obtained between .01 and 10.0 mM hydrogen peroxide with a detection limit of 3.0 µM from flow injection amperometric current–time curves recorded in pH 7.0 phosphate buffer at –100 mV and a 2.0 mL min−1 flow rate. The novelty of this work relies on its use of a laboratory-constructed flow cell constructed for the pencil graphite electrode using these inexpensive, disposable, and electrochemically reactive modified electrodes for the amperometric determination of hydrogen peroxide in a flow injection analysis system.

Simple and sensitive detection of 4-nitrophenol in real water samples using gold nanoparticles modified pretreated graphite pencil electrode

A novel, simple, sensitive and disposable gold nanoparticles modified pretreated graphite pencil electrode (AuNPs-PGPE) has been developed to overcome the surface fouling of carbon electrodes due to polymerization of phenols. The unmodified PGPE electrode displayed distinct electrocatalytic properties while reducing 4-nitrophenol (4-NP). The PGPE was prepared using a simple electrochemical treatment step of the bare GPE in NaOH solution, and the resulting electrode exhibited highly sensitive, selective and fast performance towards the determination of 4-NP. The influence of various voltammetric techniques as well as other related factors affecting the reduction peak current of 4-NP was investigated. The reduction current against 4-NP concentration at PGPE displayed a good linearity between 0.01 μM to 0.8 μM with R2 = 0.9994. The PGPE was further modified by AuNPs to increase the working range of PGPE for sensing 4-NP. Both of the developed PGPE and AuNPs-PGPE could be employed to a vast concentration range of 4-NP varying between 0.01 and 100 μM. The modified electrodes were successfully tested at different amounts of 4-NP varying form low concentration 0.2 μM to high concentration i.e. 25 μM in water models.

Electrochemical determination of paracetamol in pharmaceutical tablet by a novel oxidative pretreated pencil graphite electrode

The present paper reports the preparation of a novel, sensitive, and low-cost electrochemical sensor for the determination of paracetamol (PAR). The main strategy of this study lies on providing the surface of a pencil graphite electrode (PGE) with various oxygen-bearing functional groups by in situ oxidative pretreatment, which enables the PGE with larger surface area to adsorb PAR efficiently and mediates electron transfer. The developed oxidative pretreated PGE (OP-PGE) sensor was used for the first time to determine PAR from pure and commercial tablet dosage forms. Surface morphology of the OP-PGE was characterized by scanning electron microscopy (SEM) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR). Electrochemical behavior of PAR on the OP-PGE was investigated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under optimized experimental conditions, the linear dynamic range of calibration was between 0.052–2.85 μM with a detection limit of 18.4 nM (S/N = 3). The OP-PGE showed a good sensitivity, selectivity, and stability compared to the bare PGE. Results revealed that the OP-PGE could successfully determine PAR from the tablets with no tedious electrode fabrication and sample pretreatment methods, and in situ oxidative pretreatment could be an alternative, simple and sensitive approach for the fabrication of PGE-based electrodes to use them in the pharmaceutical analysis in the future studies.

Rapid voltammetric method for quinine determination in soft drinks

A novel voltammetric assay for quinine (QN) determination using an electrochemically pretreated pencil graphite electrode is described. The detection limit of QN was 2 × 10−7 M. The method possesses some obvious advantages including extreme simplicity, rapid response, and low cost.

An Integrative Medical Perspective on Novel Dopamine Detection Method

Dopamine is very important neurotransmitter and the rapid and effective methods for its determination are of great importance in fundamental medical research. A rapid voltammetric assay for dopamine (DA) detection in presence of ascorbic acid (AA) based on an electrochemically pretreated pencil graphite electrode has been investigated. Differential pulse voltammetry results showed two well-distinguished oxidation peaks for DA and AA at 0.369 V and 0.142 V, respectively, and the method was applied for DA determination without previous separation. The obtained detection limit for DA was 5.17 � 10-8 M. The method has been successfully applied for determination of DA in a pharmaceutical sample.

Pretreated Pencil Graphite Electrode as a Versatile Platform for Easy Measurement of Diclofenac Sodium in a Number of Biological and Pharmaceutical Samples

A pretreated pencil graphite electrode (PPGE) as an electrochemical sensor was developed and applied to measure diclofenac sodium (DIC). The effects of both potentiostatic and potentiodynamic strategies in the electrochemical pretreatment and performance of the electrode were studied, and it was concluded that the former offers better analytical sensitivity for electroanalytical purposes. PPGE displayed good electrocatalytic activity in comparison to nonpretreated PGE (NPGE). Differential pulse voltammetry (DPV) was used to determine DIC. Therefore, a calibration graph was plotted between the variation of anodic peak currents and the DIC concentration, which was found to be linear in the range 0.23–12.95 μmol/L with the detection limit (S/N = 3) of 0.12 μmol/L. PPGE was utilized to determine DIC in real samples such as biological and pharmaceutical ones, and the good recovery values obtained demonstrated the high accuracy of the modified electrode.

Electrochemical study of hydrochlorothiazide on electrochemically pre-treated pencil graphite electrode as a sensor

An electrochemical anodic behavior of hydrochlorothiazide (HCTZ) was studied by using electrochemically pretreated pencil graphite electrode (EPPGE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). Two anodic peaks were observed at peak potential 842mV and 1091mV on EPPGE at phosphate buffer (pH7.0). Electrooxidation process of HCTZ shows diffusion-controlled process on EPPGE. DPV and SWV show a good linearity in the concentration range 4μM to 140μM and 1μM to 20μM, respectively. The limits of detection were found to be 3.25μML−1 and 0.421μML−1, respectively. Electrochemical impedance spectra (EIS) gave the charge transfer resistance at EPPGE (32.3kΩ) and PGE (867kΩ), which shows an increase in the electron transfer rate at EPPGE than that of PGE. Surface area, sensitivity and electron transfer kinetic parameters were studied. Electrochemical pretreatment is a simpler method compared to other modifications for the electrodes and this method could be applied for the sensitive determination of HCTZ present in pharmaceutical formulations and urine samples.

Electrochemical detection of DNA damage induced by Bleomycin in the presence of metal ions

A simple and inexpensive electrochemical methodology was used to develop a new method to inspect the biochemical action of Bleomycin (BLM). Furthermore, the effect of some metal ions such as Fe(II), Fe(III), Cu(I), Cu(II), Zn(II), Mn(II) and Co(II) on the operation of BLM was investigated. To prove the role of ionic metals some chelators and reducers were used too. In this study, a pretreated pencil graphite electrode (PGE) modified with gold nanoparticles (AuNPs) and a synthesized zinc(II)-Schiff base complex (ZnSB) decorated with ds-DNA was used to identify DNA damage induced by BLM in the presence of metal ions. The change in the charge transfer resistance (Rct) using EIS method as well as appearance of 8-Oxo guanine (8-OxoG) peak in DPV method after immersion of the DNA biosensor in BLM solution were used as indicators of DNA damage. Our results showed that the BLM alone cannot destroy DNA and in the other words the BLM has not any interaction with ds-DNA but BLM in the presence of some metal ions can destroy the ds-DNA. By comparing the performance of metal ions and investigation of their effect on action of BLM, the mechanism of DNA damage induced by BLM was presented.

Preparation of electrochemically treated nanoporous pencil-graphite electrodes for the simultaneous determination of Pb and Cd in water samples.

A simple and rapid analytical method of determining Pb2+ and Cd2+ in water samples using an electrochemically pretreated pencil-graphite electrode (EP-PGE) is proposed for the first time in the literature. An electrochemically pretreated pencil-graphite electrode was prepared by performing potential cycling between -0.3V and 2.0V in 0.1molL-1 H3PO4 solution to improve its ability to electrochemically sense Pb2+ and Cd2+ ions. Square-wave anodic stripping voltammetry (SWASV) was used as the electroanalytical method. The electroanalytical parameters that influence the stripping determination of Pb2+ and Cd2+ were optimized based on experimental results. The magnitude of the peak oxidation current was adjusted in order to optimize the value of each parameter. Applying the resulting disposable electrode under the optimized conditions led to good selectivity and sensitivity in the determination of Pb2+ and Cd2+ ions. Interference from coexisting ions was also investigated. The resulting sensor was successfully tested by applying it to a standard reference water sample. Under the optimized conditions, the limits of detection were 0.46μgL-1 for Pb2+ and 1.11μgL-1 for Cd2+ using the electrode. Relative standard deviations (%RSD) were 2.76 for Pb2+ and 2.85 for Cd2+. The linear working ranges of the electrode for Pb2+ and Cd2+ ion detection were 5-45μgL-1 and 10-40μgL-1, respectively. Graphical abstract Preparation of nanoporous pencil-graphite electrode by cyclic voltammetry and stripping voltammetric screening of Pb and Cd.

Trace Determination of Hg(II) in Human Saliva Using Disposable Electrochemically Pretreated Graphite Pencil Electrode Surfaces.

An electrochemically pretreated graphite pencil electrode (PGPE) was designed to assay trace levels of Hg(II) in human saliva. The GPE was pretreated in 0.1 mol/L nitric acid by cycling the potential between -1.6 and -0.6 V for 60 cycles at a scan rate of 50 mV/s. The effects of pretreatment conditions, including media constituents, pH, and various electrochemical techniques and parameters, were analyzed and optimum conditions determined. Square wave anodic stripping voltammetry (SWASV) was used for the determination of Hg(II). The calibration curve obtained under optimum conditions showed that the linear range of the PGPE was from 10.0 × 10-9 mol/L to 175.0 × 10-9 mol/L with a detection limit of 3.0 × 10-9 mol/L (S/N = 3). Relative to non-pretreated GPE surfaces, electrochemical pretreatment improved the electrochemical performance of GPE surfaces in detecting Hg(II). The present analytical method was used to measure Hg(II) released from dental amalgam in human saliva.

Pretreated Graphite Pencil Electrode Based Voltammetric Sensing of Albendazole

Electrochemical behavior of albendazole was investigated at a pre-treated pencil graphite electrode (PTPGE) by cyclic voltammetry in phosphate buffer solution. The Pre-treated pencil graphite electrode showed excellent electro-catalytic activity towards the oxidation of albandazole in phosphate buffer solution of pH 3.0. From the electrochemical studies of scan rate, the overall electrode process was diffusion controlled. The pH effect suggested that equal number of protons and electrons were involved in the electrochemical detection of albendazole. Under the optimum conditions the peak current was linear to the concentration of albandazole in the range 250 μM to 1450 μM for PTPGE and the detection limit (LOD) was found to be 5.42 nM. The interference studies showed that the modified electrode exhibited excellent selectivity in the presence of large excess of interfering substances. The proposed method was successfully applied for the determination of albendazole in the spiked urine and pharmaceutical samples.