Pretreated Pencil Graphite Electrode Research Articles

Flow Injection Amperometric Analysis of H2O2 at Platinum Nanoparticles Modified Pencil Graphite Electrode

AbstractA Pt nanoparticle modified Pencil Graphite Electrode (PGE) was proposed for the electrocatalytic oxidation and non‐enzymatic determination of H2O2 in Flow Injection Analysis (FIA) system. Platinum nanoparticles (PtNPs) electrochemically deposited on pretreated PGE (p.PGE) surface by recording cyclic voltammograms of 1.0 mM of H2PtCl6 solution in 0.10 M KCl at scan rate of 50 mV s−1 for 30 cycles. Cyclic voltammograms show that the oxidation peak potential of H2O2 shifts from about +700 mV at bare PGE to +50 mV at PtNPs/p.PGE vs. Ag/AgCl /KCl (sat.). It can be concluded that PtNPs/p.PGE exhibits a good electrocatalytic activity towards oxidation of H2O2. Then, FI amperometric analysis of H2O2 was performed under optimized conditions using a new homemade electrochemical flow cell which was constructed for PGE. Linear range was found as 2.5 μM to 750.0 μM H2O2 with a detection limit of 0.73 μM (based on Sb/m of 3). As a result, this study shows the first study on the FI amperometric determination of H2O2 at PtNPs/p.PGE which exhibits a simple, low cost, commercially available, disposable sensor for H2O2 detection. The proposed electrode was successfully applied to determination of H2O2 in real sample.

Simultaneous electrochemical determination of acetaminophen and metoclopramide at electrochemically pre-treated disposable graphite pencil electrode

<p class="PaperAbstract"><span lang="EN-US">A sensitive and economic voltammetric method was developed for the simultaneous determination of acetaminophen (AMP) and metoclopramide (MCP) using pre-treated graphite pencil electrode (PTGPE). Compared to a graphite pencil electrode, the pre-treated electrode showed an apparent shift of the oxidation potentials in the positive direction and a notable enhancement in the current responses for both AMP and MCP. Cyclic voltammetry (CV) was used to study the voltammetric behavior of the drugs, while differential pulse voltammetry (DPV) was used to determine AMP and MCP simulta­neously. The dependence of the current on scan rate, pH and concentration was investi­gated to boost the experimental conditions for simultaneous determination. The calibra­tion curves were obtained over the range of 0.1</span><span lang="EN-US">×</span><span lang="EN-US">10<sup>-7</sup> to 1.1</span><span lang="EN-US">×</span><span lang="EN-US">10<sup>-7</sup> M, the concentration of each of both the drugs was varied by keeping the other constant, and achieved lower detection limit of 3.25 nM for AMP and 1.16 nM for MCP. The developed method was found to be selective, and rapid for the simultaneous determination of AMP and MCP. The proposed method was applied simultaneously in real samples and pharmaceutical samples, with satisfactory results.</span></p>

Simultaneous electrochemical determination of acetaminophen and metoclopramide at electrochemically pre-treated disposable graphite pencil electrode

<p class="PaperAbstract"><span lang="EN-US">A sensitive and economic voltammetric method was developed for the simultaneous determination of acetaminophen (AMP) and metoclopramide (MCP) using pre-treated graphite pencil electrode (PTGPE). Compared to a graphite pencil electrode, the pre-treated electrode showed an apparent shift of the oxidation potentials in the positive direction and a notable enhancement in the current responses for both AMP and MCP. Cyclic voltammetry (CV) was used to study the voltammetric behavior of the drugs, while differential pulse voltammetry (DPV) was used to determine AMP and MCP simulta­neously. The dependence of the current on scan rate, pH and concentration was investi­gated to boost the experimental conditions for simultaneous determination. The calibra­tion curves were obtained over the range of 0.1</span><span lang="EN-US">×</span><span lang="EN-US">10<sup>-7</sup> to 1.1</span><span lang="EN-US">×</span><span lang="EN-US">10<sup>-7</sup> M, the concentration of each of both the drugs was varied by keeping the other constant, and achieved lower detection limit of 3.25 nM for AMP and 1.16 nM for MCP. The developed method was found to be selective and rapid for the simultaneous determination of AMP and MCP. The proposed method was applied simultaneously in real samples and pharmaceutical samples, with satisfactory results.</span></p>

Investigation of specific interactions between Nile blue and single type oligonucleotides and its application in electrochemical detection of hepatitis C 3a virus

In this study, development of an electrochemical DNA biosensor based on a hepatitis C virus probe was introduced using an electrochemically pre-treated pencil graphite electrode (PPGE) as a transducer and Nile blue (NB) as an electroactive indicator. At first, the electrochemical behaviour of NB on the PPGE was investigated. Then, elucidating the specific interaction of NB with each of the nucleotides of DNA, the interactions of NB with oligonucleotides containing only one base type were studied. In this study, four 18-mer oligonucleotides of poly A, poly T, poly C, and poly G were used as probe and were used as related complementary/non-complementary sequences in the hybridization section. The extent of hybridization was evaluated based on the difference between DPV signals of NB accumulated on the probe–PPGE and NB accumulated on the probe–target–PPGE. Then, the developed biosensor was applied successively for the detection of short sequences of Hepatitis C 3a virus (14 pic). The hybridization between the probe (14 pic) and its complementary sequence (C2Comp) as the target was studied. Some hybridization experiments with non-complementary oligonucleotides also showed that the suggested DNA sensor responds selectively to the target. Diagnostic performance of the developed biosensor was described and the detection limit was found to be 1.1 nM with a relative standard deviation of 3.5 % in the 0.1-M Tris–HCl buffer solution (pH 7.0) containing 20 mM NaCl.

Adsorptive Square Wave Voltammetric Determination of Acyclovir and Its Application in a Pharmacokinetic Study Using a Novel Sensor of β-Cyclodextrin Modified Pencil Graphite Electrode

Abstract An electrochemical sensor for acyclovir (ACV) based on polymerization of β-cyclodextrin (β-CD) on electrochemically pretreated pencil graphite electrode (PGE) was built for the first time. A synergistic effect of β-CD was used to construct this sensor for quantification of this important drug. Scanning electron microscope (SEM) images show that polymer of β-CD has been successfully modified on the electrode. Square wave voltammetry (SWV) exhibited two linear dynamic ranges of 5 × 10−8 to 6 × 10−7 M and 1 × 10−6 to 9 × 10−6 M of ACV for its oxidation and the detection limit was found to be as low as 7.59 × 10−9 M of ACV. The parameters affecting ACV oxidation were investigated. The prepared electrodes showed good fabrication reproducibility. The analytical applications of the prepared electrodes were tested by using ACV dosage forms and human urine as a real sample. The SWV analysis has been successfully applied to pharmacokinetic studies of ACV in health human volunteers after oral administration of a single dose of Zovirax suspension (400 mg/5 mL).

RETRACTED: Electrochemical ds-DNA-based biosensor decorated with chitosan modified multiwall carbon nanotubes for phenazopyridine biodetection

A simple and inexpensive method was used to develop a novel electrochemical sensor for the determination of phenazopyridine hydrochloride (PAP). Differential pulse voltammetry was used for the electrochemical investigation of the interaction of PAP with calf thymus ds-DNA at a pencil graphite electrode (PGE) based on the reduced oxidation signals of guanine and adenine. The biosensor was constructed using pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with ds-DNA. The reductions in the intensities of guanine and adenine oxidation signals after their interaction with PAP were used as indicators for the sensitive determination of PAP. The differences observed between adenine and guanine oxidation signals (of the ds-DNA) before and after their interaction with PAP were found to be directly proportional to PAP concentration, which was used for quantitative inspections. Under optimum conditions, a linear dependency was observed between guanine and adenine oxidation signals and PAP concentration in the range of 0.01–50 µg/mL with a detection limit of 0.003 µg/mL. The method was also found to be highly selective and was successfully employed for the determination of PAP in real samples such as human plasma and urine.

Voltammetric determination of tannic acid in beverages using pencil graphite electrode

Vu D.L., Ertek B., Dilgin Y., Cervenka L. (2015): Voltammetric determination of tannic acid in beverages using pencil graphite electrode. Czech J. Food Sci., 33: 72-76. The pretreated pencil graphite electrode (Pre-PGE) prepared by a chronoamperometry technique was applied for the determination of tannic acid using anodic stripping differential pulse voltammetry. The currents obtained from voltammetry measurements at optimum conditions were linearly correlated with the concentration of tannic acid. Calibration curve was obtained for tannic acid in the concentration range of 5.0-500 × 10 -9 mol/l. The limit of detec - tion was found to be 1.5 × 10 -9 mol/l. The content of tannic acid in beverage samples determined with Pre-PGE was in good agreement with that obtained by the standard spectrophotometric method.

Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead.

In this paper, a pencil graphite electrode was pretreated using chronoamperometry technique in phosphate buffer solution (pH=7.0) for sensitive determination of quercetin. Oxidation of quercetin was investigated using pretreated pencil graphite electrode and anodic stripping differential pulse voltammetry. Under optimal conditions, the anodic current of quercetin exhibited linear response to its concentration in the range from 0.001 to 1.5 µmol/L with the limit of detection of 0.3·10-3 µmol/L. The proposed method was successfully applied for the determination of quercetin in cranberry and blackcurrant juices with recovery rate from 93.2 to 94.7%. Solid-phase extraction was found to be necessary prior to voltammetric determination of quercetin in fruit juice samples using pretreated pencil graphite electrode.

Development of a novel voltammetric sensor for the determination of methamphetamine in biological samples on the pretreated pencil graphite electrode

We developed a simple and reliable sensor for the determination of methamphetamine without expensive and time-consuming pretreatments using PPGE.

Impedimetric DNA-biosensor for the study of anti-cancer action of mitomycin C: Comparison between acid and electroreductive activation

An electrochemical protocol is described for direct monitoring of anti-cancer properties of MMC. Using electrochemical impedance spectroscopy, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and poly(diallyldimethylmmonium chloride), PDDA, decorated with ds-DNA was employed in this study to identify DNA damages induced by MMC. The change in charge transfer resistance after incubation of the DNA-biosensor in MMC solution for a known time was used as indication of DNA damage. It was found that MMC did not interact with DNA. As MMC does not inherently possess any anti-cancer activity, it is, therefore, necessary to activate it by either of two ways: activation in acidic media or electrochemical activation. Incubation of DNA-modified electrode in activated MMC led to alterations in DNA and changes in its electrochemical properties (which forms the theme of the present study). Acid and electroreductive MMC activations were compared and different adducts were subsequently generated, suggesting that the drug can bind to DNA in more than one way. Impedance spectroscopy was used for the first time as a novel technique for detecting DNA-drug adducts.

Biosensor based on ds-DNA decorated chitosan modified multiwall carbon nanotubes for voltammetric biodetection of herbicide amitrole

The interaction of amitrole and salmon sperm ds-DNA was studied using UV–vis and differential pulse voltammetry (DPV) at both bare and DNA-modified electrodes. Amitrole showed an oxidation peak at 0.445V at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV–vis spectra showed that the absorption intensity of the ds-DNA at 260nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs–CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025–2.4ngmL−1 amitrole with a detection limit of 0.017ngmL−1. The sensor showed a good selectivity and precision for the determination of amitrole. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity.

Simultaneous determination of dopamine and uric acid in biological samples on the pretreated pencil graphite electrode

An electrochemically pretreated pencil graphite electrode (PGE) has been proposed for simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of high levels of ascorbic acid (AA). The electrochemical pretreatment of PGE was achieved in phosphate buffer (pH 7) by the potential recycling between 1.5–2.0V/SCE for 100 cycles, and at the scan rate of 100mVs−1. The influence of electrochemical pretreatment of PGE on the separation of overlapped peaks of AA, DA and UA were studied and optimum conditions were suggested. Differential pulse voltammetry (DPV) was used for simultaneous determination of DA and UA in the presence of high concentrations of AA. The peak separation between DA and AA, and also between DA and UA was up to 260 and 160mV, respectively. The calibration curves were in the range of 0.15–15μM and 0.3–150μM for DA and UA in the presence of AA, respectively. The detection limits (S/N=3) were 0.033 and 0.12μM for DA and UA, respectively. The results reveal that pretreatment of the pencil graphite electrode surface not only improves its electrochemical catalytic activities towards the oxidation of DA and UA, but also resolves the overlapped oxidation peaks of AA, DA and UA into three well-defined peaks. The present method can apply for UA and DA determination in human serum and urine, and also for some commercial pharmaceutical samples without additional sample pre-treatment.

Determination of uric acid in biological samples on the pretreated pencil graphite electrode

The electrochemical behavior of uric acid (UA) has been investigated on the pretreated pencil graphite electrode (PPGE). PPGE was prepared by potentiodynamic pretreatment of pencil lead in phosphate buffer solution (pH 7). On non-pretreated pencil graphite electrode (NPGE), ascorbic acid (AA) and uric acid (UA) both exhibit totally irreversible anodic peaks which overlap each other. While on PPGE, anodic peak of AA shifts to negative potentials with a decrease in peak current; but that of UA exhibits only an increase in peak current. This behavior on PPGE results in significant resolution of UA and AA peaks, which provides the voltammetric determination of UA in the presence of AA (ΔEp ≈ 320 mV). The electrochemical oxidation of UA on PPGE being a totally irreversible process is controlled by diffusion. The kinetic parameters such as charge transfer coefficient, α, and catalytic rate constant, kh, were determined for UA at PPGE. At optimum conditions of solution pH and pulse amplitude, differential pulse voltammetry (DPV) was used for determination of UA, which exhibits a linear calibration graph of Ipversus UA concentration in the range of 1–160 μM with a correlation coefficient of 0.997. The calculated detection limit for S/N = 3 was 1.9 × 10−7 M. Finally, PPGE was used for determination of UA in biological samples such as human serum and urine, using the standard addition procedure. The obtained results were compared with those of standard spectrophotometric method, which reveals that no significant difference exists at 95% confidence level between the results of these two procedures.

Easy modification of pencil graphite electrode for discrimination and determination of morphine in biological and street samples

The electrochemical sensor was developed for discrimination and determination of morphine (MO) using an electrochemically pretreated pencil graphite electrode (PPGE). A potentiostatic strategy was employed for the electrochemical pretreatment of the electrode. The PPGE has displayed very good electrochemical catalytic activities as compared with the non-pretreated PGE (NPGE). At the PPGE, two well-defined anodic peaks of morphine at about 0.35 V and +0.80 V were observed. There is only a weak oxidation peak at +0.50 V at NPGE at the same morphine concentration, while the peak cannot be found at +0.80 V. The pretreatment of the polished PGE by electrostatic procedure at 1.80 V for 5 min in 0.50 M phosphate buffer solution of pH 7.0 was proposed as the optimum pretreatment procedure. Differential pulse voltammetry (DPV) and hydrodynamic amperometry were used for determination of MO. A calibration graph plotted by the variation of anodic peak currents as a function of MO concentration was linear in the range of 1–100 μM. The detection limit calculated from calibration graph was 0.26 μM. The PPGE was used for determination of MO in real samples, including human urine and street drug samples such as opium, heroin and heroin-crack, and the results were quite promising.

A novel sensitive DNA–biosensor for detection of a carcinogen, Sudan II, using electrochemically treated pencil graphite electrode by voltammetric methods

A simple and inexpensive methodology was used to develop a novel electrochemical sensor for the determination of Sudan II. The interaction of Sudan II with salmon sperm ds-DNA on the surface of salmon sperm ds-DNA-modified pencil graphite electrode (PGE) and in solution phase was studied, using differential pulse voltammetry. The difference between adenine and guanine signals of the ds-DNA after and before interaction with Sudan II was directly proportional to Sudan II concentration, which used for quantitative inspections. Using PGE, a linear calibration curve (R2=0.9958) was observed with 0.5–6.0μgmL−1 Sudan II. Furthermore, the LOD of 0.4μgmL−1 and linear range between 0.5 and 4.0μgmL−1 were achieved in solution phase. In the second part, Sudan II was determined on a pretreated pencil graphite electrode by means of adsorptive stripping differential pulse voltammetry. The peak current was linearly dependent on Sudan II concentration over the range of 0.0015–0.30μgmL−1, with a detection limit of 0.00007μgmL−1 Sudan II. Both ds-DNA-modified PGE and PPGE were applied to analyze Sudan II in real samples.

DNA-functionalized biosensor for riboflavin based electrochemical interaction on pretreated pencil graphite electrode

The interaction of riboflavin with salmon sperm double-stranded DNA based on the decreasing of the oxidation signal of guanine and adenine bases was studied electrochemically with a pencil graphite electrode (PGE) using differential pulse voltammetry. The decrease in the intensity of the guanine and adenine oxidation signals after interaction with riboflavin was used as an indicator signals for the sensitive determination of riboflavin. Under the optimum conditions, a linear dependence of the guanine and adenine oxidation signals was observed for the riboflavin concentration in the range of 0.5–70μgmL−1 with a detection limit of 0.34μgmL−1 at ds-DNA modified PGE. The reproducibility and applicability of the analysis to pharmaceutical dosage forms and urine sample were also investigated. These results showed that this DNA biosensor could be used for the sensitive, rapid, simple and cost effective detection and determination of riboflavin-ds-DNA interaction. Pretreated pencil graphite electrode (PPGE) was also used for the determination of riboflavin by differential pulse adsorptive stripping voltammetry. With PPGE, a linear relationship was obtained for riboflavin over the concentration range of 0.003–0.88μgmL−1 with differential pulse adsorptive stripping voltammetric signal and with a detection limit of 0.076ngmL−1. Both determination methods were fully validated and applied for the analysis of riboflavin.