Browsing by Author "Senturk, Zuhre"

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Adsorptive Stripping Voltammetric Determination of Higenamine on a Boron-Doped Diamond Electrode Improved by the Use of an Anionic Surfactant
(Elsevier Science Sa, 2020) Allahverdiyeva, Shabnam; Pinar, Pinar Talay; Keskin, Ertugrul; Yunusoglu, Oruc; Yardim, Yavuz; Senturk, Zuhre
The present work describes the first electroanalytical investigation and a new voltammetric method for a cheap, rapid and simple determination of higenamine at a surface of mildly-oxidized boron-doped diamond electrode (at +1.6 V during 180 s). The oxidation of compound was strongly dependent on pH. The sensitivity of method was significantly improved in the presence of anionic surfactant, sodium dodecyl sulfate (SDS). The first oxidation peak was chosen for the electroanalytical determination of higenamine due to its higher sensitivity compared to the other two ones. By employing square-wave stripping mode, there was a linear dependence of the oxidation peak current at +0.75 V and higenamine concentration in the range of 0.5-30.0 mg L-1 (1.84 x 10(-6)-1.11 x 10(-4) M), with a detection limit of 0.13 mg L-1 (4.79 x 10(-7) M) in BR buffer pH 2.0 containing 2 x 10(-4) M SDS (after 30 s accumulation at open-circuit condition). As an example, the practical applicability of the proposed method was tested with the quantification of higenamine in the commercial dietary supplement formulations, with results in good agreement to those obtained declared by high-performance liquid chromatography with diode-array detection as a reference method.
Analysis of Carcinogenic Polycyclic Aromatic Hydrocarbons (Pahs): an Overview of Modern Electroanalytical Techniques and Their Applications
(Bentham Science Publ Ltd, 2013) Senturk, Zuhre
A number of Polycyclic Aromatic Hydrocarbons (PAHs) have been shown to be toxicants, and induce carcinogenic and immunotoxic effects. Since PAHs are often present in low concentrations and it may be difficult to determine them in complex matrices, it is therefore essential to use powerful analytical tools to separate and identify the analyses in the samples. In this paper, initially, a short description of the principles, instrumentation, and use of common extraction and analytical techniques for PAH pollutants and their metabolites will be made in light of the previously reported works and major reviews. Special attention will be given to the use of modern polarographic and voltammetric techniques on the mercury and different types of solid electrodes, together with their some practical applications. The main drawbacks and limitations of these methods will also be discussed.
Analytical Methods for Determination of Selective Serotonin Reuptake Inhibitor Antidepressants
(Walter de Gruyter Gmbh, 2011) Senturk, Zuhre; Saka, Cafer; Tegin, Ibrahim
Selective serotonin reuptake inhibitors (SSRIs) are commonly used to treat depression. SSRIs are classified as fluoxetine, paroxetine, escitalopram, citalopram, sertraline, and fluvoxamine. Several methods have been published for the determination of SSRI drugs in pharmaceuticals, biological materials and environmental samples. This review covers the analytical methods described in the literature for the determination of SSRIs and their main metabolites or some compounds belonging to the same SSRI group. The analytical methods are generally chromatography based methods coupled to different detectors, electroanalytical methods, capillary zone electrophoretic methods, and spectrometric methods.
Colorimetric and Atomic Absorption Spectrometric Determination of Mucolytic Drug Ambroxol Through Ion-Pair Formation With Iron and Thiocyanate
(Bentham Science Publ Ltd, 2010) Levent, Abdulkadir; Senturk, Zuhre
Colorimetric and atomic absorption spectrometric methods have been developed for the determination of mucolytic drug Ambroxol. These procedures depend upon the reaction of iron(III) metal ion with the drug in the presence of thiocyanate ion to form stable ion-pair complex which is extractable in chloroform. The red-colored complex was determined either colorimetrically at 510 nm or by indirect atomic absorption spectrometry (AAS) via the determination of the iron content in the formed complex. The optimum experimental conditions for pH, concentrations of Fe3+ and SCN, shaking time, phase ratio, and the number of extractions were determined. Under the proposed conditions, linearity was obeyed in the concentration ranges 4.1x10(-6) -5.7x10(-5) M (1.7-23.6 mu g mL(-1)) using both methods, with detection limits of 4.6x10(-7) M (0.19 mu g mL(-1)) for colorimetry and 1.1x10(-6) M (0.46 mu g mL(-1)) for AAS. The proposed methods were applied for the determination of Ambroxol in tablet dosage forms. The results obtained were statistically analyzed and compared with those obtained by applying the high-performance liquid chromatographic method with diode-array detection.
Determination of 7,12-Dimethylbenz[a]anthracene in Orally Treated Rats by High-Performance Liquid Chromatography and Transfer Stripping Voltammetry
(Bentham Science Publ Ltd, 2012) Yardim, Yavuz; Levent, Abdulkadir; Ekin, Suat; Keskin, Ertugrul; Oto, Gokhan; Senturk, Zuhre
A number of polycyclic aromatic hydrocarbons (PAHs) have been shown to be toxicants, and induce carcinogenic and immunotoxic effects. As a model PAH agent, 7,12-dimethylbenz[a]anthracene (DMBA) was the strongest one tested in terms of its biological activities and biotransformation. A new and simple high-performance liquid chromatographic (HPLC) method with diode-array detection at 290 nm was developed and validated for monitoring of DMBA in different matrices (serum, liver and kidney) of rats orally treated with DMBA. Furthermore, the applicability of adsorptive transfer stripping voltammetry (AdTSV) on the pencil-lead graphite electrode to these samples was illustrated using our previously reported data for bulk aqueous solutions of DMBA. HPLC and AdTSV methods, which were compatible with each other, allowed DMBA to be detected down to the levels of 3.82x10(-9) M (0.98 ppb) and 6.73x10(-9) M (1.73 ppb), respectively. Olive oil solutions of DMBA in dose 50 mg/kg were orally administered. 60 days after a single dose of DMBA, its concentrations in these biological samples from rats were measured by means of both methods. Because of rapid biotransformation, DMBA could not be detected in serum. Only low levels of the compounds were deposited unchanged in kidney whereas its levels were considerably higher in liver. These methods were also applied to the assay whether there is an influence of the intake of aqueous extracts of Hypericum Perforatum L. plant on the parent DMBA levels accumulated in rat tissues.
Determination of Vanillin in Commercial Food Product by Adsorptive Stripping Voltammetry Using a Boron-Doped Diamond Electrode
(Elsevier Sci Ltd, 2013) Yardim, Yavuz; Gulcan, Mehmet; Senturk, Zuhre
A method for the determination of food additive vanillin was developed by adsorptive stripping voltammetry. Its determination was carried out at the anodically pre-treated boron-doped diamond electrode in aqueous solutions. Using square-wave stripping mode, the compound yielded a well-defined voltammetric response in phosphate buffer, pH 2.5 at +1.14 V (vs. Ag/AgCl) (a pre-concentration step being carried out at open-circuit condition for 60 s). A linear calibration graph was obtained in the concentration range of 0.5-15.0 mu g mL(-1) (3.3 x 10(-6)-9.8 x 10(-6) mol L-1) with a detection limit of 0.024 mu g mL(-1) (1.6 x 10(-7) mol L-1). As an example, the practical applicability of the proposed method was tested for the determination of this flavouring agent in commercial pudding powder of Keshkule (Turkish milk pudding with almond flour). (C) 2013 Elsevier Ltd. All rights reserved.
Development of a Novel Electrochemical Method for the Quantitative Analysis of Vandetanib in the Presence of Anionic Surfactant Utilizing a Bare Carbon Paste Electrode
(Marmara Univ, 2024) Pinar, Pinar Talay; Mete, Cihat; Senturk, Zuhre
In this investigation, a novel electrochemical approach employing a bare carbon paste electrode (CPE) has been devised for the sensitive and expeditious quantification of the tyrosine kinase inhibitor vandetanib (VAN). VAN, a pivotal anti-tumor agent employed in various cancer types, notably medullary thyroid cancer, manifested an irreversible oxidation peak at approximately +1.17 V (vs. Ag/AgCl, 3 M NaCl) in 0.1 M HNO3, 3 , elucidated through cyclic voltammetry. The electrode reaction was determined to proceed via controlled adsorption. The study meticulously examined the influence of anionic surfactant sodium dodecyl sulfate (SDS), instrumental parameters, pH fluctuations, and the composition of the supporting electrolyte on the oxidation peak of VAN. Remarkably, the sensitivity of stripping voltammetric measurements markedly augmented upon the inclusion of 9 x 10-4 - 4 M SDS. Employing optimized parameters for SW-AdSV (square-wave adsorptive stripping voltammetry), the bare CPE demonstrated exceptional linearity within the dynamic ranges of 1.05x10-7 - 7 - 1.6x10-5 - 5 M for VAN. The limit of detection and limit of quantification were established at 2.7x10-8 - 8 and 9.0x10-8 - 8 M for VAN, respectively. Furthermore, the developed electrochemical methodology was effectively applied for the detection of VAN in spiked model serum samples.
The Effect of Ctab, a Cationic Surfactant, on the Adsorption Ability of the Boron-Doped Diamond Electrode: Application for Voltammetric Sensing of Bisphenol a and Hydroquinone in Water Samples
(Elsevier, 2021) Hoshyar, Saadi Ali; Barzani, Hemn A. H.; Yardim, Yavuz; Senturk, Zuhre
The present study introduces for the first time the effect of the cationic surfactant, cetyltrimethylammonium bromide (CTAB) on the adsorption capability of the boron-doped diamond (BDD) electrode for the sensing of environmental pollutants bisphenol A (BPA) and hydroquinone (HQ). Cathodic pretreatment of the electrode surface after an anodic pretreatment exhibited a best electrochemical response for these two phenolic compounds. The electrochemical characteristics of BPA and HQ were first sufficiently documented by cyclic voltammetry in aqueous solutions without the addition of surfactant over a shorter and longer potential range. Square-wave voltammetry was employed for a detailed study depending on the operational conditions (e.g., pH and nature of supporting electrolyte, concentration of CTAB, accumulation variables, instrumental parameters, etc.). The sensitivity of the voltammetric measurements for BPA and HQ was increased when CTAB was present in strong acidic media (more effective for BPA) due to its interaction with the neutral forms of the selected compounds on the hydrophobic surface of BDD electrode. Besides, a significant increase in the detecting sensitivity of BPA in CTAB-containing solutions could be obtained after applying an accumulation process. Using square-wave stripping mode (after 30 s accumulation at open-circuit condition) in 0.1 M H2SO4 containing 1 x 10(-4) M CTAB, the limits of detection were found to be 0.05 mu g/mL (2.19 x 10 M), and 0.23 tig/mL (2.09 x 10(-6) M) for the simultaneous determination of BPA and HQ, respectively. In this way, modification-free BDD electrode could introduce an alternative to chemically modified electrodes for the analysis of environmental samples.
Electroanalytical Determination of Enrofloxacin Based on the Enhancement Effect of the Anionic Surfactant at Anodically Pretreated Boron-Doped Diamond Electrode
(Elsevier Science Sa, 2018) Donmez, Fatih; Yardim, Yavuz; Senturk, Zuhre
In this paper, a mercury-free and modification-free electroanalytical methodology based on anodically pretreated boron-doped diamond electrode is described for the quantification of enrofloxacin. The oxidation of compound was irreversible and presented an adsorption controlled process. The sensitivity of the stripping voltammetric measurements was significantly improved when the anionic surfactant, sodium dodecylsulfate (SDS) was present in the electrolyte solution. Using square-wave stripping mode, a linear response was obtained for enrofloxacin determination in 0.1 mol L-1 HNO3 solution containing 9 x 10(-4) mol L-1 SDS at +1.27 V (vs. Ag/AgCl) (after 60 s accumulation at open-circuit condition). Linearity was found within 0.025 to 1.0 mu g mL(-1) (6.96 x 10(-8)-2.78 x 10(-6) mol L-1) with a detection limit 0.0057 mu g mL(-1) (1.59 x 10(-8) mol L-1). The proposed method could be used for the determination of enrofloxacin in pharmaceutical formulations and the spiked human urine samples with acceptable recoveries.
Electroanalytical Determination of Salbutamol in Pharmaceutical Formulations Using Cathodically Pretreated Boron-Doped Diamond Electrode
(Marmara Univ, 2018) Talay Pinar, Pinar; Ali, Hoshyar Saadi; Abdullah, Abdullah Abdulwahed; Yardim, Yavuz; Senturk, Zuhre
This paper examined for the first time the possibilities of the usage of the cathodically pretreated borondoped diamond (CPT-BDD) electrode for the redox behavior of salbutamol (SAL) using cyclic and adsorptive stripping voltammetry. The cyclic voltammograms showed an irreversible and adsorption-controlled oxidation peak at about +1.0 V in the Britton-Robinson (BR) buffer (pH 9.0) solution. Under the optimized experimental condition, using square-wave adsorptive stripping mode, the compound yielded a well-defined voltammetric response in BR buffer, pH 9.0 at +0.95 V (vs. Ag/AgCl) (after 30 s accumulation at an open circuit condition). A linear calibration graph was obtained in the concentration range of 4.15 to 83 mu g mL(-1) (1.73x10(-5) -3.47x10(-4) M). A detection limit of 1.21 mu g mL(-1) (5.06x10(-6) M) was observed. The suggested method was also applied to the determination of SAL in the drug formulations.
Electroanalytical Investigation and Determination of Hepatitis C Antiviral Drug Ledipasvir at a Non-Modified Boron-Doped Diamond Electrode
(Elsevier Science Sa, 2020) Allahverdiyeva, Shabnam; Keskin, Ertugrul; Pinar, Pinar Talay; Yunusoglu, Oruc; Yardim, Yavuz; Senturk, Zuhre
This study is about the use of the boron-doped diamond electrode pretreated electrochemically (anodic and subsequent cathodic) in the voltammetric determination of hepatitis C antiviral drug ledipasvir. Cyclic voltammetric measurements revealed that the compound yielded two well-separated irreversible oxidation peaks (P-A1 and P-A2) in acidic medium. The dependence of intensities of currents and potentials on electrode pretreatment, pH and nature of the supporting electrolyte, and other variables was investigated by square-wave voltammetry. Determination of ledipasvir was performed in Britton-Robinson buffer (pH 2.0) on the basis of both P-A1 and P-A2, which offered linear concentration ranges 0.5-60.0 mu g mL(-1) (5.6 x 10(-7)-6.8 x 10(-5) mol L-1) and 5.0-60.0 mu g mL(-1) (5.6 x 10(-6)-6.8 x 10(-5) mol L-1), respectively, with detection limits of 0.12 mu g mL(-1) (1.4 x 10(-7) mol L-1) and 0.76 mu g mL(-1) (8.6 x 10(-7) mol L-1). The practical applicability of developed methodology was tested by the assay of a fixed-dose combination tablet with sofosbuvir.
Electroanalytical Investigation and Voltammetric Quantification of Antiviral Drug Favipiravir in the Pharmaceutical Formulation and Urine Sample Using a Glassy Carbon Electrode in Anionic Surfactant Media
(Tubitak Scientific & Technological Research Council Turkey, 2022) Akca, Zeynep; Ozok, Hande Izem; Yardim, Yavuz; Senturk, Zuhre
This work describes the electrochemical investigation of a promising antiviral agent, favipiravir (FAV) utilizing a nonmodified glassy carbon (GC) electrode, along with a unique voltammetric approach that can determine FAV with a good degree of accuracy, speed, and cost-effectiveness. Using cyclic voltammetry, the compound demonstrated a single well-defined and an irreversible oxidation peak at approximately +1.12 V (vs. Ag/AgCl) in Britton-Robinson (BR) buffer at pH 10.0. The synergistic effect of anionic surfactant, sodium dodecyl sulfate (SDS) on the adsorption ability of GC electrode remarkably increased the sensitivity of the stripping voltammetric measurements of FAV. Employing square-wave adsorptive stripping voltammetry at +1.17 V (vs. Ag/AgCl) (after 60 s accumulation at open-circuit condition) in BR buffer (pH 10.0) containing 3 x 10(-4) M SDS, the linear relationship is found for FAV quantification in the concentration from 1.0 to 100.0 mu g mL(-1) (6.4 x 10(-6)-6.4 x 10(-4) M) with a detection limit of 0.26 mu g mL-1 (1.7 x 10(-6) M). The proposed approach was used successfully to determine FAV in pharmaceutical formulations and model human urine samples.
Electrochemical and Analytical Performance of Cathodically Pretreated Boron-Doped Diamond Electrode for the Determination of Oxazolidinone Antibiotic Linezolid in Cationic Surfactant Media
(Elsevier Science Sa, 2020) Pinar, Pinar Talay; Senturk, Zuhre
The electrochemical oxidation of an oxazolidinone class of antibiotic, Linezolid (LNZ) was studied in aqueous as well as aqueous/surfactant media on a commercially available boron-doped diamond (BDD) electrode pretreated cathodically. By using cyclic voltammetry, LNZ showed two couples of oxidation/reduction peak in aqueous solutions. The electrode process is pH-dependent and controlled by diffusion. The compound yielded two well-separated oxidation steps in acidic, neutral and alkaline media by employing square-wave voltammetry. The sensitivity of the voltammetric measurements was improved when the cationic surfactant, cetyltrimethylammonium bromide (CTAB) was present in the electrolyte solution at pH 4.0. In Britton-Robinson buffer containing 0.9 mM CTAB, the calibration curves were linear for both oxidation peaks (Ia and IIa) over concentration ranges of 0.25-6.41 mu g mL(-1) (0.74-19.27 mu M), with detection limits of 0.05 mu g mL(-1) (0.15 mu M) for Ia, and 0.12 mu g mL(-1) (0.34 mu M) for IIa. The practical applicability of developed methodology was tested in pharmaceutical formulations.
Electrochemical Determination of Fluoroquinolone Antibiotic Norfloxacin in the Presence of Anionic Surfactant Using the Anodically Pretreated Boron-Doped Diamond Electrode
(Wiley-v C H verlag Gmbh, 2020) Karahan, Fatih; Basi, Zehra; Keskin, Ertugrul; Pinar, Pinar Talay; Yardim, Yavuz; Senturk, Zuhre
In this article, a simple, fast and inexpensive methodology has been developed for the determination of fluoroquinolone class antibiotic norfloxacin (NFX) in anionic surfactant media (sodium dodecyl sulphate, SDS) using an anodically pretreated boron-doped diamond (APT-BDD) electrode. Cyclic voltammetric studies showed that the NFX gave an irreversible and adsorption controlled anodic oxidation signal at a potential of about +1.32 V on the APT-BDD electrode. The effects of parameters such as the electrode pre-treatment procedure, SDS concentration, and instrumental variables on the electrochemical sensitivity of NFX were evaluated. Under optimized conditions, the linearity was achieved in the range of 0.05 to 4.0 mu g mL(-1) (1.57x10(-7)-1.25x10(-5) mol L-1), with a detection limit of 0.013 mu g mL(-1) (4.07x10(-8) mol L-1) by using square-wave adsorptive stripping voltammetry (SW-AdSV). The feasibility of the developed approach for the quantification of NFX in urine samples was tested.
Electrochemical Determination of Norepinephrine by Adsorptive Stripping Voltammetry Using a Bare Boron-Doped Diamond Electrode
(Editura Acad Romane, 2019) Keskin, Ertugrul; Yardim, Yavuz; Levent, Abdulkadir; Senturk, Zuhre
A boron-doped diamond electrode was used for the first time for sensitive and selective analysis of norepinephrine (NE) using square wave voltammetry (SWV) technique. NE displayed one welldefined, irreversible and adsorption-controlled oxidation peak at about +0.85 V (vs. Ag/AgCl) in Britton-Robinson buffer (BR, 0.1 M, pH 2.0) using cyclic voltammetry (CV) technique. The effect of supporting electrolyte, solution pH and instrumental variables on oxidation peak current were optimized. In optimal experiment conditions, it was found that there was an excellent correlation between oxidation peak current and NE concentration in the range of 1 to 100 mu g mL(-1) (4.9X10(-6) M-4.9 x10(-4) M) with a detection limit of 0.254 mu g mL(-1) (1.2X10(-6) M) in 0.1 M BR buffer (pH 2.0) solution employing square-wave stripping mode. The developed technique can be used for the quantification of NE in the pharmaceutical formulation with acceptable recoveries.
Electrochemical Determination of Pterostilbene at a Cathodically Pretreated Boron-Doped Diamond Electrode Using Square-Wave Adsorptive Anodic Stripping Voltammetry in Cationic Surfactant Media
(Elsevier Science Sa, 2016) Yigit, Aydin; Yardim, Yavuz; Zorer, Ozlem Selcuk; Senturk, Zuhre
In the present paper, an electrochemical method was developed for the determination of pterostilbene (a phenolic phytoalexin) using adsorptive anodic stripping voltammetry at a cathodically pretreated boron doped diamond electrode. The oxidation of compound was irreversible and exhibited an adsorption controlled process which is of pH dependence. The sensitivity of the stripping voltammetric measurements was significantly improved in the presence of cationic surfactant, cetyltrimethylammonium bromide (CTAB). Using square-wave stripping mode, a highly linear analytical curve was obtained for pterostilbene determination in 0.1 M HNO3 solution containing 2 x 10(-4)M CTAB at +0.78V (vs. Ag/AgCl) (after 30 s accumulation at open-circuit condition). The process could be used in the range of 0.005-1.0 mu g mL(-1) (2.0 x 10(-8)-3.9 x 10(-6)M), with a detection limit of 0.0011 mu gmL(-1) (4.3 x 10(-9) M). The proposed method was successfully applied to measure the concentration of pterostilbene in the commercial dietary supplements, with results similar to those obtained using a HPLC method at 95% confidence level. As far as it could be verified, the proposed method is the first one based on the electrochemical investigation of pterostilbene. (C) 2016 Elsevier B.V. All rights reserved.
Electrochemical Evaluation and Adsorptive Stripping Voltammetric Determination of Capsaicin or Dihydrocapsaicin on a Disposable Pencil Graphite Electrode
(Elsevier, 2013) Yardim, Yavuz; Senturk, Zuhre
Capsaicin and dihydrocapsaicin are the two most abundant capsaicinoids in peppers, which are responsible for about 90% of the spiciness. A detailed study of the electrochemical properties of these compounds at pencil graphite (PG) electrode was carried out in the pH range 1.0-12.0 in aqueous solutions. The compounds underwent irreversible oxidation at PG electrode, which was an adsorption-controlled process with two protons and two electrons. The voltammetric data indicated that their oxidation proceeded via an ECE mechanism. Using the square-wave adsorptive stripping voltammetry with accumulation at a fixed potential of -0.1 V for 120 s, both of them yielded a well-defined voltammetric response at +0.31 V (vs. Ag/AgCl) in Britton-Robinson buffer, pH 9.0. Capsaicin and dihydrocapsaicin could be determined with detection limits of 1.12 ng mL(-1) (3.7 x 10(-9) M) and 0.28 ng mL(-1) (9.1 x 10(-10) M), respectively. The practical applicability of this methodology was tested in commercial Turkish pepper products. The concentration of total capsaicinoids was determined using capsaicin as standard. (C) 2013 Elsevier B.V. All rights reserved.
Electrochemical Performance of Boron-Doped Diamond Electrode in Surfactant-Containing Media for Ambroxol Determination
(Elsevier Science Sa, 2014) Levent, Abdulkadir; Yardim, Yavuz; Senturk, Zuhre
A novel application of boron-doped diamond electrode is introduced for the determination of ambroxol, a potential antioxidant drug belonging to the expectorant class. The electrochemical oxidation of ambroxol was first investigated by cyclic voltammetry using boron-doped diamond and glassy carbon electrodes in aqueous solutions both with and without the addition of surfactant. The compound was irreversibly oxidized in one/two steps at high positive potentials, resulting in the formation of a couple with a reduction and re-oxidation wave at less positive potentials. Special attention was given to the use of adsorptive stripping voltammetry at a surface of mildly oxidized boron-doped diamond electrode in aqueous solutions over the pH range of 1.0-10.0. Addition of anionic surfactant (sodium dodecylsulfate) to ambroxol-containing electrolyte enhanced the stripping current signal. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in phosphate buffer pH 2.5 containing 4 x 10(-4) M sodium dodecylsulfate at +1.02V (versus Ag/AgCl) (after 30s accumulation at +0.50V). The process could be used to determine ambroxol in the concentration range of 0.05-0.7 mu M, with a detection limit of 0.010 mu M (4.2 ng mL(-1)). The suggested method was successfully applied to pharmaceuticals and spiked human urine samples. (C) 2014 Elsevier B.V. All rights reserved.
Electrooxidation of Tetracycline Antibiotic Demeclocycline at Unmodified Boron-Doped Diamond Electrode and Its Enhancement Determination in Surfactant-Containing Media
(Elsevier, 2021) Allahverdiyeva, Shabnam; Yardim, Yavuz; Senturk, Zuhre
In this paper, for the first time, the study of voltammetric determination of tetracycline antibiotic demeclocycline was conducted. The oxidation of compound was investigated using a commercially available boron-doped diamond electrode pretreated electrochemically (anodic and subsequent cathodic). Addition of anionic surfactant, sodium dodecylsulfate (SDS) and cationic surfactant, cetyltrimethylammonium bromide (CTAB) to the demeclocycline-containing electrolyte solution at pH 2.0 and 9.0, respectively, was found to improve the sensitivity of the stripping voltammetric measurements. Employing square-wave stripping mode (after 30 s accumulation at open-circuit condition) in Britton-Robinson buffer, the limits of detection were found to be 1.17 mu g mL(-1) (2.3 x 10(-6) M) for 4 x 10(-4) SDS-containing buffer solution at pH 2, and 0.24 mu g mL(-1) (4.8 x 10(-7) M) for 1 x 10(-4) CTAB-containing buffer solution at pH 9.0. The feasibility of the developed approach for the quantification of demeclocycline was tested in urine samples.
Electrooxidation of Thiourea and Its Square-Wave Voltammetric Determination Using Pencil Graphite Electrode
(Walter de Gruyter Gmbh, 2011) Levent, Abdulkadir; Keskin, Ertugrul; Yardim, Yavuz; Senturk, Zuhre
The electrochemical properties of thiourea (TU) were investigated in pH range 2.0-12.0 by cyclic and square-wave voltammetry. The compound was irreversibly oxidized at a pencil graphite electrode in one or two oxidation steps which are pH-dependent. Based on the voltammetric peak for the second oxidation process of TU in phosphate buffer at pH 12.0, a square-wave voltammetric method was proposed for the determination of the compound in the range 6.3-30 mu m, with a detection limit of 1.29 mu m. The applicability to direct assays of wastewaters was also tested.