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Adsorption of Selected Amino Acids at the Mercury/Aqueous Solution Interface from the Chlorate (VII) and Its Dependence on the Supporting Electrolyte Concentration
(Sage Publications Inc, 2015) Nosal-Wiercinska, Agnieszka; Grochowski, Mariusz; Wisniewska, Malgorzata; Tyszczuk-Rotko, Katarzyna; Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen
In this study, we compared the adsorption of methionine, cysteine and cystine at the mercury/chlorate (VII) interface. Changes in the surface tension with the potential of the zero charge gamma(z) and relative surface excess Gamma' of methionine, cysteine and cystine as a function of their concentration indicate that the adsorption of the studied amino acids increases in the order of methionine > cystine > cysteine. For all the systems examined, linear dependences ln[x(1-Theta)/Theta = f(Theta)] (Frumkin isotherm) and ln (Gamma'/c) = f (Gamma') (virial isotherm) were obtained. Changes in the adsorption parameters as a function of the supporting electrolyte concentration indicate the competitive adsorption of amino acids and ClO4- ions and electrostatic interactions between the water dipoles and adsorbates in the double layer.
Determination of Ascorbic Acid in Tablet Dosage Forms and Some Fruit Juices by DPV
(Esg, 2008) Yilmaz, Selehattin; Sadikoglu, Murat; Saglikoglu, Gulsen; Yagmur, Sultan; Askin, Gokce
Ascorbic acid, a water-soluble vitamin, is the most common electroactive biological compound found in some fruit species. The electrochemical oxidation of ascorbic acid was investigated at glassy carbon electrode in various aqueous solutions in the pH range of 0.64-10.15 (in Britton-Robinson, acetate, phosphate buffers and 0.5 mol L-1 sulphuric acid solutions) by cyclic (CV) and differential pulse (DPV) voltammetry. For the quantitative purposes, a very well-resolved diffusion-controlled voltammetric peak was obtained in 0.2 mol L-1 acetate buffer (pH 3.49) at 0.342 V by DPV technique. The linear response was obtained in the concentration range of 6x10(-6)-8x10(-4) mol L-1 with a detection limit (LOD) of 5.17x10(-7) and quantitative limit (LOQ) of 1.72x10(-6) mol L-1. Ascorbic acid in pharmaceutical dosage forms and some fruit juices were determined by DPV. The reliability of the proposed voltammetric technique was established by recovery studies.
Direct Determination of Zn Heavy Metal in Tap Water of Canakkale (TURKEY) by Anodic Stripping Voltammetry Technique
(Electrochemical Science Group, 2009) Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen; Sadikoglu, Murat
In this work, the direct determination of zinc heavy metal in the tap water was carried out by differential pulse anodic stripping voltammetry (DPASV) technique at the glassy carbon electrode (GCE). The zinc ions were deposited by reduction at -1.5 V on a bare glassy carbon surface. Then, the deposited metal was oxidized by scanning the potential of the electrode surface from -1.5 to -0.8 volt using a differential puls mode. The stripping current arising from the oxidation of metal was connected with the concentration the metal in the sample. The concentration of zinc heavy metal found in tap water sample was determined to be 180 mu g L(-1) using 0.2 mol L(-1) acetate buffer (pH: 3.50).
Electroanalytical and HPLC Methods for the Determination of Oxcarbazepine in Spiked Human Urine and Tablet Dosage Form
(Croatian Chemical Soc, 2014) Nosal-Wiercinska, Agnieszka; Yilmaz, Selehattin; Binel, Sevcan; Yagmur, Sultan; Saglikoglu, Gulsen; Sadikoglu, Murat; Yıldız, Mustafa
In this study, the electrochemical reduction and determination of oxcarbazepine were easily realized in various buffer solutions in the pH range of 4.50 to 11.15 in real samples using glassy carbon electrode (GCE) by cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. The influence of pH on the cathodic peak current and peak potential was investigated. Scan rate studies were also completed. The diffusion controlled nature of the peak was established. The best results for the quantitative determination of oxcarbazepine were obtained by DPV technique in Britton-Robinson (BR) buffer (pH 8.05). In this basic medium, one irreversible and sharp cathodic peak was observed. A linear calibration curve for DPV analysis was constructed in the oxcarbazepine concentration range of 8x10(-6) to 1x10(-4) M. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.65x10(-6) and 5.51x10(-6) M, respectively. Repeatability, reproducibility, precision and accuracy of the developed technique were checked in spiked human urine and tablet dosage forms by recovery studies and results of the high performance liquid chromatography (HPLC) technique. A reduction mechanism for the electrode reaction was proposed.
Electroanalytical determination of metronidazole in tablet dosage form
(Serbian Chemical Soc, 2013) Yilmaz, Selehattin; Baltaoglu, Esra; Saglikoglu, Gulsen; Yagmur, Sultan; Polat, Kamran; Sadikoglu, Murat
In this study, the electrochemical reduction and determination of metronidazole were easily realized in Britton-Robinson buffer (pH 4.01) using an UTGE by cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques. In this acidic medium, one irreversible and a sharp cathodic peak were observed. A linear calibration curve for DPV analysis was constructed in the metronidazole concentration range 3 x10(-6)-9x10(-5) mol L-1. The limit of detection (LOD) and limit of quantification (LOQ) were 1.42x10(-7) and 4.76x10(-7) mol L-1 respectively.
Electrocatalytic Oxidation of Acyclovir on Poly(p-Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode
(Wiley-V C H Verlag Gmbh, 2015) Can, Saide; Yilmaz, Selehattin; Saglikoglu, Gulsen; Sadikoglu, Murat; Menek, Necati
Acyclovir is an antiviral effective drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in phosphate buffer solution (PBS). The polymer film-modified electrode was used to electrochemically detect acyclovir. Polymer film showed excellent electrocatalytic activity for the oxidation of acyclovir. The anodic peak potential value of the acyclovir at the poly(p-ABSA) modified glassy carbon electrode was 950mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the acyclovir concentration range 2x10(-7)-9x10(-6)molL(-1). Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 5.57x10(-8) and 1.85x10(-7)molL(-1) respectively. The proposed method exhibits good recovery and reproducibility.
Electrochemical Determination of Phenazopyridine Hydrocloride using Poly(p-Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode
(Esg, 2015) Demirtas, Cigdem; Yilmaz, Selehattin; Saglikoglu, Gulsen; Sadikoglu, Murat
Phenazopyridine hydrochloride is an antiviral effective drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in phosphate buffer solution (PBS). The electrochemical properties of the polymer film were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The polymer film-modified electrode was used to electrochemically detect phenazopyridine hydrochloride. Polymer film showed excellent electrocatalytic activity for the reduction of phenazopyridine hydrochloride. The catodic peak potential value of the phenazopyridine hydrochloride at the poly(p-ABSA) modified glassy carbon electrode was -334 mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the phenazopyridine hydrochloride concentration range 6x10(-6)-1x10(-5) mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 2.1x10(-7) and 7x10(-7) mol L-1 respectively. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization of p-ABSA are also suggested.
Electrochemical Investigation of Isoniazid on Poly (p-Aminobenzene Sulfonic Acid) Film Modified Glassy Carbon Electrode
(Esg, 2015) Demirbilek, Esra; Saglikoglu, Gulsen; Yilmaz, Selehattin
Isoniazid is a tuberculostatic agent effective active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in phosphate buffer solution (PBS). The electrochemical properties of isoniazid on modified electrode were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The polymer film-modified electrode was used to electrochemically detect isoniazid. The polymer film had excellent electrocatalytic activity for the oxidation of isoniazid. A linear calibration curve for DPV analysis was constructed in the isoniazid concentration range 2x10(-5) - 1x10(-4) mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.05x10(-6) and 1.01x10(-5) mol L-1 respectively. Isoniazid was determined in tablet dosage form. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization were also suggested.
Electrochemical investigation of isoniazid on poly (p-aminobenzene sulfonic acid) film modified glassy carbon electrode
(Electrochemical Science Group, 2014) Demirbilek, Esra; Saglikoglu, Gulsen; Yilmaz, Selehattin
Isoniazid is a tuberculostatic agent effective active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in phosphate buffer solution (PBS). The electrochemical properties of isoniazid on modified electrode were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The polymer film-modified electrode was used to electrochemically detect isoniazid. The polymer film had excellent electrocatalytic activity for the oxidation of isoniazid. A linear calibration curve for DPV analysis was constructed in the isoniazid concentration range 2x10-5- 1x10-4 mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 3.05x10-6 and 1.01x10-5 mol L-1 respectively. Isoniazid was determined in tablet dosage form. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization were also suggested. © 2015 The Authors.
Fabrication of AuNPs/PHCQE/GPE electrochemical sensor for the determination of isoniazid
(Elsevier Inc., 2025) Baycan, Fatma; Saglikoglu, Gulsen
In this study, we have developed an electrochemical sensor based conjugated polymer to determine the compound isoniazid. Isoniazid is a drug-active substance widely used in the treatment of tuberculosis. To determine isoniazid electrochemically, 3-(5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-3-9-hexyl-9H-carbazole-3-yl)quinoxalin-2-yl)-9-hexyl-9H-carbazole monomer was first electropolymerized on a graphite pencil electrode and then gold nanoparticles were doped on it. The prepared electrode showed excellent electrocatalytic activity for the oxidation of isoniazid. The electrochemical behavior of isoniazid was examined, and oxidation of isoniazid was determined by the Cyclic Voltammetry technique as a diffusion controlled. The linearity range of isoniazid was calculated 3–100 µM and the detection limit was 0.310 ?M by using differential pulse voltammetry. An electrochemical sensor was successfully applied to the determination of isoniazid in tablet dosage forms. The suggested method provides good recovery, wide linearity range and low detection limit. In addition, interference, repeatability, reproducibility and stability studies were carried out. © 2025 Elsevier B.V.
Impact of water activity on double layer parameters at the mercury/chlorates(VII) interface in the presence of mixed adsorption layers of 6-mercaptopurine-Triton X-100
(Springer, 2019) Nosal-Wiercinska, Agnieszka; Kaliszczak, Waldemar; Drapsa, Anna; Wisniewska, Malgorzata; Yilmaz, Selehattin; Yagmur, Sultan; Saglikoglu, Gulsen
Adsorption mechanism of 6-mercaptopurine, 6-mercaptopurine-Triton X-100 on the mercury electrode surface from 2, 4 and to 6 mol dm(-3) chlorates(VII) was studied as the function of adsorbate bulk concentration. The experimental data obtained from the measurements of differential capacity of the double layer were used, namely the measurements of zero charge potential and surface tension at the zero charge potential. In the case of mixed adsorption layer of 6-mercaptopurine-Triton X-100 domination of 6MP in adsorption equilibria formation as well as competitive adsorption between the 6-mercaptopurine-Triton X-100 molecules were found. Significant contribution of water molecules in the adsorption-desorption processes was also observed.
Investigation of Competitive and Noncompetitive Adsorption of Some Heavy Metals Ions on Leucodon sciuroides (Hedw.) Schwagr
(Amer Chemical Soc, 2020) Ucarli, Okan; Yayintas, Ozlem Tonguc; Engin, Mehmet Soner; Cay, Seydahmet; Saglikoglu, Gulsen; Yilmaz, Selehattin
Heavy metals are an important pollutant group. Adsorption is one of the methods used to remove heavy metals from the environment. Mosses were preferred as bio-indicators because they have the capacity to accumulate many elements by their high surface-to-volume ratio. Leucodon sciuroides (Hedw.) Schwagr. (LS) are mosses that play an important part of the ecosystem and are collected from the Ida Mountain (Kazdag) region of canakkale (Turkey). For the purpose of determining the adsorption capacity of heavy metal ion (Pb2+, Cd2+, Co2+, Ni2+, Zn2+, and Cu2+) analysis conditions, pH, contact time, and adsorbent amounts were determined and the maximum adsorption capacity was calculated with the help of the relevant isotherms. Heavy metal concentrations were determined by inductively coupled plasma-mass spectrometry. It was determined that the optimum adsorption for mosses was 30 min at pH = 6.0 (the pH at which maximum adsorption occurs). The adsorption event shows that some divalent cations fit the Freundlich isotherm and some fit the Langmuir isotherm model. A pseudo-second-order reaction best fits the kinetic data for metal ions. Among the six metal ions studied, the highest adsorption was observed in Pb2+ and Cu2+ cations. According to the competitive adsorption results, the moss has a great advantage in determining the Pb(2+ )and Cu2+ cations industrially as well as other metals and in removing other metal impurities from the environment. Also, LS is exploited as a biosorbent to remove metal ions from aqueous solutions and can be used as a biomarker.
Sensitive Detection of Ornidazole by Poly(p-Aminobenzene Sulfonic Acid)-Modified Glassy Carbon Electrode
(Bentham Science Publ Ltd, 2014) Saglikoglu, Gulsen; Yilmaz, Selehattin
Ornidazole is an antibacterial drug active compound. A glassy carbon electrode (GCE) was modified with an electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in pH 7.0 phosphate buffer solution (PBS). The electrochemical properties of the polymer film were studied using cyclic voltammetry (CV) and different pulse voltammetry (DPV) techniques. The polymer film-modified electrode was used to electrochemically detect ornidazole. The polymer film showed excellent electrocatalytic activity for the reduction of ornidazole. The cathodic peak potential value of the ornidazole at the p-ABSA modified glasy carbon electrode was -513 mV obtained by DPV. A linear calibration curve for DPV analysis was constructed in the ornidazole concentration range 8x10(-7) -5x10(-5) M. Limit of detection (LOD) and limit of quantification (LOQ) were 1.00x10(-7) and 3.32x10(-7) M respectively. The DPV technique proposed was successfully applied to the detection of ornidazole in tablet dosage forms. Precision and accuracy of the developed technique were checked by recovery studies. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization of p-ABSA and reduction of ornidazole at p-ABSA-modified GCE are also suggested.
Sensitive Electrochemical Determination of Oxcarbazepine using Polymer Film Modified Glassy Carbon Electrode
(Esg, 2015) Apaydin, Esra Rukiye; Saglikoglu, Gulsen; Yilmaz, Selehattin; Yıldız, Mustafa
A glassy carbon electrode (GCE) is modified with electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in pH 7.0 phosphate buffer solution (PBS). A poly(p-ABSA) modified glassy carbon electrode was used for the voltammetric determination of oxcarbazepine. The modified electrode exhibited excellent electrocatalytic activity for the reduction of oxcarbazepine. The voltammetric response of oxcarbazepine at this polymer film modified electrode increased significantly when compared with that at a bare glassy carbon electrode. The proposed method was applied to the quantification of oxcarbazepine in pharmaceutical formulations. The proposed method exhibits good recovery and reproducibility. The mechanisms of electropolymerization of p-ABSA and reduction of oxcarbazepine are also suggested.
Sensitive voltammetric determination of famotidine in human urine and tablet dosage forms using an ultra trace graphite electrode
(Serbian Chemical Soc, 2014) Yagmur, Sultan; Yilmaz, Selehattin; Saglikoglu, Gulsen; Uslu, Bengi; Sadikoglu, Murat; Ozkan, Sibel A.
In this study, the direct and sensitive determination of famotidine based on its electrochemical oxidation was investigated in spiked human urine and tablet dosage forms. The electrochemical measurements were performed in various buffer solutions in the pH range 0.88-12.08 at an ultra trace graphite electrode (UTGE) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results were obtained for the quantitative determination of famotidine by the DPV technique in 0.5 mol L-1 H2SO4 solution (pH 0.30). In this strong acid medium, one irreversible anodic peak was observed. The effects of pH and scan rate on the peak current and peak potential were investigated. The diffusion-controlled nature of the peak was established. For optimum conditions described in the experimental section, a linear calibration curve for DPV analysis was constructed in the famotidine concentration range 2x10(-6)-9x10(-5) mol L-1. The limit of detection (LOD) and limit of quantification (LOQ) were 3.73x10(-7) and 1.24x10(-6) mol L-1 at a UTGE, respectively. The repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine and tablet dosage forms.
Sensitive Voltammetric Determination of Paracetamol on Poly(4-Aminobenzene Sulfonic Acid) Modified Glassy Carbon Electrode
(Esg, 2016) Yilmaz, Selehattin; Bas, Zeynep; Sadikoglu, Murat; Yagmur, Sultan; Saglikoglu, Gulsen
A poly (4-aminobenzene sulfonic acid) (4-ABSA) modified glassy carbon electrode (GCE) was prepared for the quantitative determination of paracetamol (PCT). The 4-ABSA-modified GCE was prepared by electrochemical polymerization method in phosphate buffer solution (PBS) (pH 7.0). The polymer film-modified electrode has high catalytic ability for electrooxidation of PCT, which appeared at pH range of 5-8 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results for the determination of PCT were obtained by DPV in PBS (pH 7.00). Calibration curve was obtained in the PCT concentration range of 6x10(-7) to 9x10(-6) mol L-1 by DPV. Limit of detection (LOD) and quantification (LOQ) were found as 9.33x10(-8) mol L-1 and 3.10x10(-7) mol L-1, respectively. The results of experiments indicated that modified electrode have good stability, sensitivity and reproducibility for at least one month if stored dry in air.
Synthesis, spectroscopic studies and electrochemical properties of Schiff bases derived from 2-hydroxy aromatic aldehydes and phenazopyridine hydrochloride
(Serbian Chemical Soc, 2013) Yagmur, Sultan; Yilmaz, Selehattin; Saglikoglu, Gulsen; Sadikoglu, Murat; Yıldız, Mustafa; Polat, Kamran
Novel Schiff bases 1-4 were synthesized by the reaction of 2-hydroxybenzaldehyde, 2-hydroxy-5-methoxybenzaldehyde, 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde with phenazopypridine hydrochloride (PAP), respectively, and their structures were elucidated by means of spectroscopic techniques. The electrochemical reduction of PAP and its Schiff bases (1-4) were realized on a glassy carbon electrode (GCE) in dimethyl sulfoxide (DMSO) using the cyclic voltammetric (CV) technique. The effect of functional groups on reduction potential of the Schiff bases was investigated. A general electrochemical reduction mechanism of the compounds is suggested.
Voltammetric detection of biosorption of Co, Ni, Zn, Cd, Pb, and Cu on Hypnum cupressiforme Hedw. in aquatic media
(Springer Wien, 2022) Yayintas, Ozlem Tonguc; Cay, Seydahmet; Engin, Mehmet Soner; Ucarli, Okan; Saglikoglu, Gulsen; Yilmaz, Selehattin
In this study, the concentration of six heavy metal ions biosorbed at Hypnum cupressiforme Hedw. (HC), moss determined by voltammetric methods. While determining the optimum biosorption conditions, it was found that the amount of biosorbent 0.1 g, the contact time of metal ions-mosses is 30 min. The biosorption event shows that Ni2+ and Cu2+ appropriate the Langmuir isotherm and sequence of biosorption % was explained for covalent radii of these metals. Pb2+, Cd2+, Co2+, Zn2+, appropriate the Freundlich isotherm model and sequence of biosorption % was explained for the ratio of the hydration number to the hydrated radii of these metals. Biosorption results indicated that HC can be used for removing metal ions from aqueous solutions.
Voltammetric Determination of Acyclovir in Human Urine Using Ultra Trace Graphite and Glassy Carbon Electrodes
(Bentham Science Publ Ltd, 2011) Sadikoglu, Murat; Saglikoglu, Gulsen; Yagmur, Sultan; Orta, Erdem; Yilmaz, Selehattin
An electroanalytical method was developed for the direct quantitative determination of Acyclovir (Acy) in spiked human urine base on its oxidation behavior. The electrochemical oxidation and determination of Acy were easily carried out on ultra trace graphite electrode (UTGE) and glassy carbon electrode (GCE) using a variety of voltammetric techniques. The electrochemical measurements were carried out on these electrodes in various buffer solutions in the pH range of 3.66 to 9.08 by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The best results for the quantitative determination of Acy were obtained by DPV technique in 0.2 M acetate buffer (pH=4.66). In this acidic medium, one irreversible anodic peak was observed. The anodic peak current and peak potential depend on pH and scan rate were studied. The diffusion controlled nature of the peak was established. Acy was determined in the concentration range from 4x10(-6) to 7x10(-5) molL(-1) for UTGE and 2.0x10(-6) to 1.0x10(-4) molL(-1) for GCE by the applied electroanalytical procedure. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 1.0x10(-6) and 3.3x10(-6) molL(-1) on UTGE and 3.5x10(-7) and 1.2x10(-6) molL(-1) on GCE, respectively. Repeatability, precision and accuracy of the developed technique were checked by recovery studies in spiked urine.
Voltammetric sensitive determination of metronidazole at poly(p-aminobenzene sulfonic acid)-modified glassy carbon electrode
(Pleiades Publishing Inc, 2015) Saglikoglu, Gulsen; Yilmaz, Selehattin
A glassy carbon electrode (GCE) was modified with electropolymerized film of p-aminobenzene sulfonic acid (p-ABSA) in pH 7.0 phosphate buffer solution (PBS). The polymer film showed excellent electrocatalytic activity for the reduction of metronidazole. The DPV technique proposed was successfully applied to the detection of metronidazole in tablet dosage forms. Precision and accuracy of the developed technique were checked by recovery studies.

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