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A low-cost, fast, disposable and sensitive biosensor study: flow injection analysis of glucose at poly-methylene blue-modified pencil graphite electrode
(Springer, 2018) Dilgin, Didem Giray; Ertek, Bensu; Dilgin, Yusuf
In this work, firstly methylene blue (MB) was electropolymerized onto pencil graphite electrode (PGE) surface for the electrocatalytic oxidation of NADH. Cyclic voltammograms show that oxidation potential of NADH at Poly-MB/PGE shifted to negative direction about 300 mV compared with bare PGE. These results indicate that Poly-MB/PGE exhibits a good electrocatalytic activity toward NADH oxidation. Then, a glucose biosensor study was performed based on the determination of enzymatically generated NADH by glucose dehydrogenase (GDH) which immobilized onto Poly-MB/PGE using glutaraldehyde cross-linking procedure. The biosensing of glucose in flow injection analysis (FIA) system was performed at GDH/Poly-MB/PGE for the first time. The electrocatalytic oxidation currents of enzymatically produced NADH obtained from FI amperometric current-time curves recorded at + 200 mV and in phosphate buffer solution at pH 7.0 containing 1.0 M KCl were linearly related to the concentration of glucose. Linear calibration plots are obtained in the concentration range from 0.01 to 1.0 mM. The limit of detection (LOD) was found to be 4.0 mu M. A fast, sensitive, low-cost and disposable glucose biosensor was constructed in FIA system using GDH/Poly-MB/PGE; therefore, it might provide a new perspective for the fabrication of biosensor of other compounds such as glutamate, lactate and alcohol.
Amperometric determination of sulfide based on its electrocatalytic oxidation at a pencil graphite electrode modified with quercetin
(Elsevier, 2012) Dilgin, Yusuf; Kizilkaya, Bayram; Ertek, Bensu; Erena, Nuri; Dilgin, Didem Giray
This study describes a new approach for the investigation of electrocatalytic oxidation of sulfide using a pencil graphite electrode modified with quercetin (PGE/QH(2)). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/QH(2) showed a significant electrocatalytic activity toward sulfide oxidation. Cyclic voltammetric studies show that the peak potential of sulfide shifts from +450 mV at bare PGE to +280 mV at PGE/QH(2). The electrocatalytic currents obtained from amperometric measurements at +300 mV vs. Ag/AgCl/KClsat and at pH 8.0 BR buffer solution containing 0.1 M NH4Cl were linearly related to the concentration of sulfide. The calibration graph consisted of two linear segments of 1-20 mu M and 20-800 mu M with a detection limit of 0.3 mu M (based on 3s(b)). The proposed method was successfully applied to the determination of sulfide in waste waters and was compared with the spectrophotometric method. (C) 2012 Elsevier B.V. All rights reserved.
DETERMINATION OF ANTI-CANCER DRUG EMODIN USING A SILICA-GEL-MODIFIED CARBON PASTE ELECTRODE
(Soc Brasileira Quimica, 2014) Vu, Dai Long; Ertek, Bensu; Dilgin, Yusuf; Cervenka, Libor
In this paper, a silica-gel-modified carbon paste electrode (Si-gel/ CPE) was used to determine the anti-cancer drug emodin by anodic stripping differential pulse voltammetry (ASDPV). The effects of the silica-gel content, the pH of the supporting electrolyte, and the scan rate on the oxidation current of emodin were investigated. The oxidation currents of emodin obtained from ASDPV measurements were linearly correlated with the concentration in the range of 5.0 x 10(-9) to 300.0 x 10(-9) mol L-1. The limit of detection was determined to be 1.5 x 10(-9) mol L-1. The current method was successfully applied to determine emodin in a knotweed root sample, with recovery rate of 92.5% to 98.3%.
Determination of Tannic Acid Using Silica Gel Modified Carbon Paste Electrode
(Esg, 2013) Dai Long Vu; Ertek, Bensu; Cervenka, Libor; Dilgin, Yusuf
In this paper, silica gel modified carbon paste electrode (Si-gel/CPE) was used for the determination of tannic acid (TA) by anodic stripping differential pulse voltammetry (ASDPV). The influences of pH values, amount of silica gel, accumulation potential and time on the signal enhancement of TA were optimized, and a novel electrochemical method for the determination of TA was reported. The currents obtained from ASDPV measurements at optimum conditions were linearly correlated with the concentration of TA. Calibration curve was obtained for TA concentrations in the range of 1 - 1000x10(-9) mol l(-1). The limit of detection was found to be 0.3x10(-9) mol l(-1). The results from TA measurements by Si-gel/CPE were in good agreement with those obtained from the standard spectrophotometric method.
Differential pulse voltammetric determination of eugenol at a pencil graphite electrode
(Elsevier Science Bv, 2016) Saglam, Ozlem; Dilgin, Didem Giray; Ertek, Bensu; Dilgin, Yusuf
In this study, the electrochemical behavior of eugenol, a widely used herbal drug, was investigated at a pencil graphite electrode (PGE). A low-cost, disposable, sensitive and selective electrochemical sensor is proposed for the determination of eugenol by recording its differential pulse voltammograms in Britton-Robinson buffer solution containing 0.1 M KCl with pH of 2.0 at the PGE. The PGE displayed a very good electrochemical behavior with significant enhancement of the peak current compared to a glassy carbon electrode. Under experimental conditions, the PGE had a linear response range from 0.3 mu M to 50.0 mu M eugenol with a detection limit of 0.085 mu M (based on 3S(b)). Relative standard deviations of 2.4 and 4.8% were obtained for five successive determinations of 30.0 and 5.0 mu M eugenol, respectively, which indicate acceptable repeatability. This voltammetric method was successfully applied for the direct determination of eugenol in real samples. The effect of various interfering compounds on the eugenol peak current was also studied. (C) 2015 Elsevier B.V. All rights reserved.
Electrocatalytic Oxidation of NADH Using a Pencil Graphite Electrode Modified with Hematoxylin
(Amer Scientific Publishers, 2012) Dilgin, Yusuf; Ertek, Bensu; Kizilkaya, Bayram; Dilgin, Didem Giray; Gokcel, H. Ismet
In the present study, the electrocatalytic oxidation of reduced p-Nicotinamide Adenine Dinucleotide (NADH) was investigated using a pencil graphite electrode modified with hematoxylin (PGE/HMT). The PGE/HMT was prepared by adsorption of HMT on the PGE via immersion of bare PGE into 1.0 mM HMT solution (in methanol) for 60 s at room temperature. Cyclic voltammetric studies show that the peak potential of NADH oxidation shifts from +450 mV at bare PGE to +200 mV at PGE/HMT. The electrocatalytic currents obtained from the amperometric measurements at +200 mV versus Ag/AgCl/KClsat and pH 7.0 phosphate buffer solution containing 0.1 M KCl were linearly related to the concentration of NADH. The calibration graph consisted of two linear segments of 0.5-10 mu M and 10-300 mu M with a detection limit of 0.2 mu M (based on 3s(b), s(b) is the standard deviation of the blank response). The amperometric measurements exhibited that the response of the modified PGE/HMT towards the oxidation of NADH is reproducible, fast, sensitive and stable. Finally, the results obtained in the present study conclusively show that PGE modified with HMT can be effectively used to detect NADH.
Electrocatalytic oxidation of sulphide using a pencil graphite electrode modified with hematoxylin
(Elsevier Science Sa, 2012) Dilgin, Yusuf; Kizilkaya, Bayram; Ertek, Bensu; Isik, Firat; Dilgin, Didem Giray
The present study describes a new approach for the investigation of electrocatalytic oxidation of sulphide using a pencil graphite electrode modified with hematoxylin (PGE/HMT). Adsorption procedure was used for the preparation of the modified electrodes. It was observed that PGE/HMT showed a significant electrocatalytic activity toward sulphide oxidation. Cyclic voltammetric studies showed that the peak potential of sulphide shifted from +480 mV at bare PGE to +220 mV at PGE/HMT. The electrocatalytic currents obtained from amperometric measurements at +200 mV versus Ag/AgCl/KClsat and at pH 8.0 BR buffer solution containing 0.1 M KCl were linearly related to the concentration of sulphide. The calibration graph consisted of a linear segment of 1-200 mu M with a detection limit of 0.4 mu M (based on 3s(b)). The proposed method was successfully applied to the determination of sulphide in waste waters and was compared with the spectrophotometric method. (C) 2012 Elsevier B.V. All rights reserved.
Fenoksazin türü boyar madde modifiye elektrot kullanılarak NADH'nin eelektrokatalitik yükseltgenmesine ışığın etkisi
(Çanakkale Onsekiz Mart Üniversitesi, 2010) Ertek, Bensu; Dilgin, Yusuf
Bu çalışmada, fenoksazin türü boyar maddelerden olan brilliant kresil mavisi ve nil mavisi olmak üzere farklı redoks mediyatörüyle elektropolimerizasyon yöntemi kullanılarak modifiye camımısı karbon elektrotlar hazırlanmış ve NADH'nin elektrokatalitik ve fotoelektrokatalitik yükseltgenmesine yönelik çalışmalar döngüsel voltammetri ve amperometri için geleneksel voltammetrik hücrede gerçekleştirilmiştir.Her bir modifiye elektrotun hazırlanması esnasındaki destek elektrolit türü veya pH'ı, monomer derişimi, döngü sayısı ve potansiyel aralığı gibi parametreler modifiye elektrot hazırlandıktan sonra NADH'ye en iyi yanıt vereceği konum dikkate alınarak optimize edilmiştir. Hazırlanan modifiye elektrotlara tarama hızının ve destek elektrolit pH'nın etkisi ile modifiye elektrotların kararlılığı döngüsel voltammetri tekniği ile incelenmiştir.NADH'nin elektrokatalitik yükseltgenmesi bu modifiye elektrotlar kullanılarak döngüsel voltammetri ve amperometri tekniği ile incelenmiş ve modifiye elektrotların NADH'ye iyi bir elektrokatalitik etki gösterdiği saptanmıştır.Aynı yöntemler kullanılarak; modifiye elektrotların yüzeyi fiber optikli bir halojen lamba ışık kaynağından elde edilen ışıkla ışıklandırılıp NADH'nin fotoelektrokatalitik yükseltgenmesi gerçekleştirilmiş ve elektrokatalitik akımın normal ışıksız olana göre yaklaşık 1,5-2 kat arttığı sonucuna varılmıştır. Her bir modifiye elektrot için NADH derişimine karşı pik akımları hem amperometrik hem de fotoamperometrik yöntemle izlenmiş ve 1x10-6 ? 1x10-3 M arasında doğrusal derişim aralığı elde edilmiştir.
Flow Injection Amperometric Detection of Sulfide Using a Prussian Blue Modified Glassy Carbon Electrode
(Japan Soc Analytical Chemistry, 2012) Ertek, Bensu; Vu, Dai Long; Cervenka, Libor; Dilgin, Yusuf
This study investigates a new approach for the electrocatalytic determination of sulfide in a flow injection analysis (FIA) system using a Prussian blue modified glassy carbon electrode (PB/GCE). The results from experiments show that PB/GCE significantly enhances the electrocatalytic activity towards sulfide oxidation. A homemade flow electrochemical cell was used to perform the electrocatalytic determination of sulfide in the FIA system. The currents obtained from amperometric measurements in the HA system at optimum conditions (carrier solution, pH 8.0; Britton-Robinson buffer solution containing 0.1 M KCl; flow rate, 1.4 mL/min; transmission tubing length, 10 cm; injection volume, 100 mu L; constant applied potential, +150 mV vs. Ag/AgCl/KClsat) were linearly correlated with the sulfide concentration. A calibration curve was obtained for sulfide concentrations in the range of 0.5 - 100 mu M. The detection limit was found to be 0.3 mu M for the amperometric method. The proposed method was successfully applied to wastewater sample. Finally, results from sulfide measurements by PB/GCE were in good agreement with those obtained from the spectrophotometric method.
Flow injection analysis of sulphide based on its photoelectrocatalytic oxidation at poly-methylene blue modified glassy carbon electrode
(Pergamon-Elsevier Science Ltd, 2012) Dilgin, Yusuf; Canarslan, Seda; Ayyildiz, Onder; Ertek, Bensu; Nisli, Gurel
A new approach for photoelectrocatalytic determination of sulphide in a flow injection analysis (FIA) system was studied using a poly-methylene blue modified glassy carbon electrode (poly-MB/GCE). Results from electrochemical measurements have revealed that poly-MB/GCE is capable of signalling electrocatalytic and photoelectrocatalytic activity towards sulphide oxidation. When the surface of poly-MB/GCE was irradiated with a light source (250W Halogen lamp), the electrocatalytic current increased substantially. A homemade flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was used to perform the photoelectrocatalytic determination of sulphide in FIA system. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (carrier solution: pH 9.0 Britton Robinson buffer solution containing 0.1 M KCl; flow rate: 1.3 mL min(-1); transmission tubing length: 10 cm; injection volume: 100 mu L; and constant applied potential: +150 mV vs. Ag/AgCl/KClcat) were linearly correlated with the sulphide concentration. The calibration curves were obtained for sulphide concentrations in a range of 0.5-500 mu M. The detection limits were found to be 0.27 and 0.15 mu M for amperometric and photoamperometric methods, respectively. The proposed method was successfully applied to different wastewaters such as municipal sewage or tannery wastewater. Finally, results from the sulphide measurements by poly-MB/GCE were in good agreement with those attained using spectrophotometric method. Clown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
Kuantum nokta modifiye elektrotlar kullanarak fotobiyosensör tasarımı ve akışa enjeksiyon sisteminde uygulanması
(Çanakkale Onsekiz Mart Üniversitesi, Lisansüstü Eğitim Enstitüsü, 2016) Ertek, Bensu; Dilgiin, Yusuf
Bu çalışmada yarı iletken kuantum nokta (Quantum dot, QD) nano parçacıklar (CdS/ZnS), çok duvarlı karbon nanotüp/camımsı karbon elektrot (GCE/MWCNT) ve kalem grafit elektrot (PGE) yüzeyine elektrokimyasal olarak biriktirilmiştir. Kuantum nokta modifiye elektrotların elektrokimyasal karakterizasyonu, Fe(CN)64-/3- içeren pH 7,0 fosfat tampon ortamında döngüsel voltammogramları ve impedans eğrileri kaydedilerek gerçekleştirilmiş ve elektrotların yüzey morfolojileri SEM görüntüleri kaydedilerek incelenmiştir. Modifiye elektrotlarla ilk olarak NADH'nin elektrokatalitik ve fotoelektrokatalitik yükseltgenmesi gerçekleştirilmiştir. Ardından glukoz dehidrogenaz (GDH) immobilize edilmiş QD modifiye PGE ve GCE/MWCNT kullanılarak akışa enjeksiyon analiz (Flow injection analysis, FIA) sisteminde glukoz biyosensörü için optimizasyon çalışmaları yapılmıştır. Glukoz ile NAD+ 'nın enzimatik tepkimesi sonucunda oluşan NADH'nin yükseltgenmesine ait akımlar izlenerek amperometrik ve fotoamperometrik glukoz biyosensörü FIA sisteminde geliştirilmiştir. Glukoz için doğrusal kalibrasyon aralığı, R2, LOD /LOQ değerleri QD modifiye PGE ve GCE/MWCNT için sırasıyla 0,2-0,8 mM (R2=0,9923), (LOD /LOQ 0,09 / 0,3 mM) ve 0,01-2,0 mM (R2=0,9971), (LOD /LOQ 0,006/0,02 mM) glukoz olarak bulunmuş ve yüzeyin ışıklandırılmasıyla akımın PGE için 2 kat, GCE/MWCNT için ise 3 kat arttığı tespit edilmiştir. Benzer sonuçlar etanol için alkol dehidrogenaz enzimi kullanılarak da elde edilmiş ve PGE ile GCE/MWCNT için sırasıyla 0,05-0,8 mM, (R2=0,9997), (LOD/LOQ 0,005/0,015 mM) ve 0,05-0,5 mM, (R2=0,9985), (LOD/LOQ 0,003/0,012 mM) etanol olarak hesaplanmıştır. Son olarak, girişim çalışmaları her iki enzim için ve ix gerçek örneklere uygulama çalışmaları glukoz dehidrogenaz için gerçekleştirilmiştir.
Photoamperometric flow injection analysis of glucose based on dehydrogenase modified quantum dots-carbon nanotube nanocomposite electrode
(Elsevier Science Sa, 2016) Ertek, Bensu; Dilgin, Yusuf
In this work, a core-shell quantum dot (QD, ZnS-CdS) was electrodeposited onto multiwalled carbon nano tube modified glassy carbon electrode (ZnS-CdS/MWCNT/GCE) and following glucose dehydrogenase (GDH) was immobilized onto QD modified electrode. The proposed electrode (GDH/ZnS-CdS/MWCNT/ GCE) was effectively used for the photoelectrochemical biosensing of glucose in flow injection analysis (FIA) system using a home-made flow cell. Results from cyclic voltammetric and FI amperometric measurements have revealed that GDH/ZnS-CdS/MWCNT/GCE is capable of signaling photoelectrocatalytic activity toward NADH when the surface of enzyme modified electrode was irradiated with a light source (250W Halogen lamp). Thus, photoelectrochemical biosensing of glucose was monitored by recording current-time curve of enzymatically produced NADH at optimized conditions. The biosensor response was found linear over the range 0.010-2.0 mM glucose with detection limits of 6.0 and 4.0 mu M for amperometric and photoamperometric methods, respectively. The relative standard deviations (n = 5) for 0.5 mM glucose were 5.8% and 3.8% for photoamperometric and amperometric results, respectively. The photoelectrochemical biosensor was successfully applied to the real samples. The results with this biosensor showed good selectivity, repeatability and sensitivity for monitoring glucose in amperometric and photoamperometric HA studies. (C) 2016 Elsevier B.V. All rights reserved.
Photoelectrocatalytic determination of NADH in a flow injection system with electropolymerized methylene blue
(Pergamon-Elsevier Science Ltd, 2011) Dilgin, Yusuf; Dilgin, Didem Giray; Dursun, Zekerya; Gokcel, H. Ismet; Gligor, Delia; Bayrak, Burcu; Ertek, Bensu
It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min(-1): transmission tubing length, 10 cm; injection volume, 100 mu L; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 x 10(-7)-2.0 x 10(-4) M. The detection limit was found to be 4.0 x 10(-8) M for photoamperometric determination of NADH. (C) 2010 Elsevier Ltd. All rights reserved.
Photoelectrochemical glucose biosensor based on a dehydrogenase enzyme and NAD+/NADH redox couple using a quantum dot modified pencil graphite electrode
(Royal Soc Chemistry, 2016) Ertek, Bensu; Akgul, Cahit; Dilgin, Yusuf
A simple, disposable and economical modified electrode was prepared by electrodeposition of hybrid quantum dots (ZnS-CdS) onto a pencil graphite electrode (PGE) surface and subsequent immobilization of glucose dehydrogenase (GDH) onto the quantum dot modified electrode (GDH/ZnS-CdS/PGE). The prepared electrode was effectively used for the photoelectrochemical determination of glucose in a flow injection analysis (FIA) system using a new home-made flow cell which was designed for PGEs for the first time. Results from the cyclic voltammetric and FI amperometric measurements revealed that the GDH/ZnS-CdS/PGE is capable of signaling photoelectrocatalytic activity involving NADH when the surface of the GDH/ZnSr-CdS/PGE is irradiated with a light source with a fiber optic cable (250 W halogen lamp). The currents of NADH produced by the enzymatic reaction in the photoamperometric FIA system under optimized conditions (carrier stream: 0.1 M phosphate buffer solution (pH 7.0) containing 1.0 M KCl and 10.0 mM NAD(+), applied potential: +0.8 V vs. Ag/AgCl/KCl(sat.); flow rate: 0.6 mL min(-1), sample loop: 100 mu L; transmission tubing length: 10 cm) were linearly correlated with the glucose concentration. Calibration curves were obtained for glucose concentrations within a range from 0.2 to 8.0 mM. The detection limits were found to be 0.09 and 0.05 mM for the amperometric and photoamperometric methods, respectively. The relative standard deviations (n = 7) for 0.5 mM glucose were 4.5% and 3.5% from the photoamperometric and amperometric results respectively. The photoelectrochemical biosensor was applied to real samples successfully. The results with this biosensor showed good selectivity, repeatability and sensitivity for monitoring glucose in amperometric and photoamperometric FIA studies.
Sensitive Voltammetric Determination of Natural Flavonoid Quercetin on a Disposable Graphite Lead
(Faculty Food Technology Biotechnology, 2015) Vu, Dai Long; Zabcikova, Simona; Cervenka, Libor; Ertek, Bensu; Dilgin, Yusuf
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 mu mol/L with the limit of detection of 0.3.10(-3) mu mol/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.
Voltammetric Determination of Tannic Acid in Beverages using Pencil Graphite Electrode
(Czech Academy Agricultural Sciences, 2015) Vu, Dai Long; Ertek, Bensu; Dilgin, Yusuf; Cervenka, Libor
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 x 10(-9) mol/l. The limit of detection was found to be 1.5 x 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.

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