TY  - JOUR
AU  - Zrinski, Ivana
AU  - Pungjunun, Kingkan
AU  - Martinez, Sanja
AU  - Zavašnik, Janez
AU  - Stanković, Dalibor M.
AU  - Kalcher, Kurt
AU  - Mehmeti, Eda
PY  - 2020
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8588
AB  - A simple and highly sensitive electrochemical biosensor based on laccase immobilized onto a gold nanoparticles/graphene nanoplatelets-modified screen-printed carbon electrode (LACC/AuNP/GNPl/SPCE) was developed for the determination of hydroquinone (HQ) and other phenolic compounds. The biosensor shows excellent electro-catalytic activity towards oxidation of hydroquinone at a potential of -0.05 V (vs Ag/AgCl, 3 M KCl) in phosphate buffer as supporting electrolyte (0.1 M, pH 7.0) using hydrodynamic amperometry. Analytical characteristics uncover that the LACC/AuNP/GNPl/SPCE comprises a wide linear range for the dependence of the signal on HQ concentrations from 4 to 130 µM with a detection limit (3σ) of 1.5 µM. The repeatability (5 measurements, 100 µM hydroquinone) is ±2% and the reproducibility (5 biosensors, 100 µM hydroquinone) is ±3%. Interference studies of most common compounds with the determination of hydroquinone demonstrated negligible effects. Finally, the biosensor and the analytical method were applied to the determination of phenolic antioxidant capacity (AOC) in wine and blueberry syrup based on Trolox (6‑hydroxy‑2,5,7,8-tetramethylchromane-2-carboxylic acid) and hydroquinone equivalents. The results were evaluated by using their calibration curves which were satisfactory and agreed well with the results obtained by the reference method Trolox Equivalent Antioxidant Capacity assay (TEAC-Assay).
T2  - Microchemical Journal
T1  - Evaluation of phenolic antioxidant capacity in beverages based on laccase immobilized on screen-printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles
VL  - 152
SP  - 104282
DO  - 10.1016/j.microc.2019.104282
ER  - 

@article{
author = "Zrinski, Ivana and Pungjunun, Kingkan and Martinez, Sanja and Zavašnik, Janez and Stanković, Dalibor M. and Kalcher, Kurt and Mehmeti, Eda",
year = "2020",
abstract = "A simple and highly sensitive electrochemical biosensor based on laccase immobilized onto a gold nanoparticles/graphene nanoplatelets-modified screen-printed carbon electrode (LACC/AuNP/GNPl/SPCE) was developed for the determination of hydroquinone (HQ) and other phenolic compounds. The biosensor shows excellent electro-catalytic activity towards oxidation of hydroquinone at a potential of -0.05 V (vs Ag/AgCl, 3 M KCl) in phosphate buffer as supporting electrolyte (0.1 M, pH 7.0) using hydrodynamic amperometry. Analytical characteristics uncover that the LACC/AuNP/GNPl/SPCE comprises a wide linear range for the dependence of the signal on HQ concentrations from 4 to 130 µM with a detection limit (3σ) of 1.5 µM. The repeatability (5 measurements, 100 µM hydroquinone) is ±2% and the reproducibility (5 biosensors, 100 µM hydroquinone) is ±3%. Interference studies of most common compounds with the determination of hydroquinone demonstrated negligible effects. Finally, the biosensor and the analytical method were applied to the determination of phenolic antioxidant capacity (AOC) in wine and blueberry syrup based on Trolox (6‑hydroxy‑2,5,7,8-tetramethylchromane-2-carboxylic acid) and hydroquinone equivalents. The results were evaluated by using their calibration curves which were satisfactory and agreed well with the results obtained by the reference method Trolox Equivalent Antioxidant Capacity assay (TEAC-Assay).",
journal = "Microchemical Journal",
title = "Evaluation of phenolic antioxidant capacity in beverages based on laccase immobilized on screen-printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles",
volume = "152",
pages = "104282",
doi = "10.1016/j.microc.2019.104282"
}

Zrinski, I., Pungjunun, K., Martinez, S., Zavašnik, J., Stanković, D. M., Kalcher, K.,& Mehmeti, E.. (2020). Evaluation of phenolic antioxidant capacity in beverages based on laccase immobilized on screen-printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles. in Microchemical Journal, 152, 104282.
https://doi.org/10.1016/j.microc.2019.104282

Zrinski I, Pungjunun K, Martinez S, Zavašnik J, Stanković DM, Kalcher K, Mehmeti E. Evaluation of phenolic antioxidant capacity in beverages based on laccase immobilized on screen-printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles. in Microchemical Journal. 2020;152:104282.
doi:10.1016/j.microc.2019.104282 .

Zrinski, Ivana, Pungjunun, Kingkan, Martinez, Sanja, Zavašnik, Janez, Stanković, Dalibor M., Kalcher, Kurt, Mehmeti, Eda, "Evaluation of phenolic antioxidant capacity in beverages based on laccase immobilized on screen-printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles" in Microchemical Journal, 152 (2020):104282,
https://doi.org/10.1016/j.microc.2019.104282 . .

TY  - JOUR
AU  - Kunpatee, Kanjana
AU  - Chamsai, Phuktra
AU  - Mehmeti, Eda
AU  - Stanković, Dalibor M.
AU  - Ortner, Astrid
AU  - Kalcher, Kurt
AU  - Samphao, Anchalee
PY  - 2019
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/8667
AB  - A sensitive and rapid method for the determination of fenobucarb by using screen-printed carbon electrode modified with graphene nanoribbons - ionic liquid - cobalt phthalocyanine (GNRs-IL-CoPc/SPCE) composites based on flow injection analysis (FIA) was developed and applied to vegetable samples. The prepared GNRs-IL-CoPc composite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Moreover, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical behavior of the modified SPCE. The amperometric current responses were obtained from the oxidation of 2-sec-butyl-phenol, which is the product of alkaline hydrolysis of fenobucarb. The optimization of chemical variables and instrumental analysis such as composite amounts, pH, applied potential, and flow rate were carried out to obtain the best measurement. Under the optimal conditions, the proposed sensor yielded sensitivity of 0.0884 M/A·cm2, a wide linear range for detection of fenobucarb from 0.025 to 110 μM with a low detection, and quantification limits of 0.0089 μM and 0.0252 μM, respectively. Additionally, the developed sensor showed good repeatability (RSD = 3.5%, n = 10 measurements) and good reproducibility (RSD = 3.9%, n = 5 sensors). The proposed method could be effectively applied for the determination of fenobucarb in vegetable samples.
T2  - Journal of Electroanalytical Chemistry
T1  - A highly sensitive fenobucarb electrochemical sensor based on graphene nanoribbons-ionic liquid-cobalt phthalocyanine composites modified on screen-printed carbon electrode coupled with a flow injection analysis
VL  - 855
SP  - 113630
DO  - 10.1016/j.jelechem.2019.113630
ER  - 

@article{
author = "Kunpatee, Kanjana and Chamsai, Phuktra and Mehmeti, Eda and Stanković, Dalibor M. and Ortner, Astrid and Kalcher, Kurt and Samphao, Anchalee",
year = "2019",
abstract = "A sensitive and rapid method for the determination of fenobucarb by using screen-printed carbon electrode modified with graphene nanoribbons - ionic liquid - cobalt phthalocyanine (GNRs-IL-CoPc/SPCE) composites based on flow injection analysis (FIA) was developed and applied to vegetable samples. The prepared GNRs-IL-CoPc composite was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Moreover, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were used to characterize the electrochemical behavior of the modified SPCE. The amperometric current responses were obtained from the oxidation of 2-sec-butyl-phenol, which is the product of alkaline hydrolysis of fenobucarb. The optimization of chemical variables and instrumental analysis such as composite amounts, pH, applied potential, and flow rate were carried out to obtain the best measurement. Under the optimal conditions, the proposed sensor yielded sensitivity of 0.0884 M/A·cm2, a wide linear range for detection of fenobucarb from 0.025 to 110 μM with a low detection, and quantification limits of 0.0089 μM and 0.0252 μM, respectively. Additionally, the developed sensor showed good repeatability (RSD = 3.5%, n = 10 measurements) and good reproducibility (RSD = 3.9%, n = 5 sensors). The proposed method could be effectively applied for the determination of fenobucarb in vegetable samples.",
journal = "Journal of Electroanalytical Chemistry",
title = "A highly sensitive fenobucarb electrochemical sensor based on graphene nanoribbons-ionic liquid-cobalt phthalocyanine composites modified on screen-printed carbon electrode coupled with a flow injection analysis",
volume = "855",
pages = "113630",
doi = "10.1016/j.jelechem.2019.113630"
}

Kunpatee, K., Chamsai, P., Mehmeti, E., Stanković, D. M., Ortner, A., Kalcher, K.,& Samphao, A.. (2019). A highly sensitive fenobucarb electrochemical sensor based on graphene nanoribbons-ionic liquid-cobalt phthalocyanine composites modified on screen-printed carbon electrode coupled with a flow injection analysis. in Journal of Electroanalytical Chemistry, 855, 113630.
https://doi.org/10.1016/j.jelechem.2019.113630

Kunpatee K, Chamsai P, Mehmeti E, Stanković DM, Ortner A, Kalcher K, Samphao A. A highly sensitive fenobucarb electrochemical sensor based on graphene nanoribbons-ionic liquid-cobalt phthalocyanine composites modified on screen-printed carbon electrode coupled with a flow injection analysis. in Journal of Electroanalytical Chemistry. 2019;855:113630.
doi:10.1016/j.jelechem.2019.113630 .

Kunpatee, Kanjana, Chamsai, Phuktra, Mehmeti, Eda, Stanković, Dalibor M., Ortner, Astrid, Kalcher, Kurt, Samphao, Anchalee, "A highly sensitive fenobucarb electrochemical sensor based on graphene nanoribbons-ionic liquid-cobalt phthalocyanine composites modified on screen-printed carbon electrode coupled with a flow injection analysis" in Journal of Electroanalytical Chemistry, 855 (2019):113630,
https://doi.org/10.1016/j.jelechem.2019.113630 . .

TY  - JOUR
AU  - Mehmeti, Eda
AU  - Stanković, Dalibor M.
AU  - Chaiyo, Sudkate
AU  - Zavasnik, Janez
AU  - Zagar, Kristina
AU  - Kalcher, Kurt
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1477
AB  - A reagentless third generation electrochemical glucose biosensor was fabricated based on wiring the template enzyme glucose oxidase (GOx) with graphene nanoribbons (GN) in order to create direct electron transfer between the co-factor (flavin adenine dinucleotide, FAD) and the electrode. The strategy involved: (i) isolation of the apo-enzyme by separating it from its co-enzyme; (ii) preparation of graphene nanoribbons (GN) by oxidative unzipping of multi-walled carbon nanotubes; (iii) adsorptive immobilization of GNs on the surface of a screen printed carbon electrode (SPCE); (iv) covalent attachment of FAD to the nanoribbons; (v) recombination of the apo-enzyme with the covalently bound FAD to the holoenzyme; and (vi) stabilization of the bio-layer with a thin membrane of Nafion. The biosensor (referred to as GN/FAD/apo-GOx/Nafion/SPCE) is operated at a potential of +0.475 V vs Ag/AgCl/{3 M KCl} in flow-injection mode with an oxygen-free phosphate buffer (pH 7.5) acting as a carrier. The signals are linearly proportional to the concentration of glucose in the range from 50 to 2000 mgai...L-1 with a detection limit of 20 mgai...L-1. The repeatability (10 measurements, at 1000 mgai...L-1 glucose) is +/- 1.4% and the reproducibility (5 sensors, 1000 mgai...L-1 glucose) is +/- 1.8%. The biosensor was applied to the determination of glucose in human serum.
T2  - Microchimica Acta
T1  - Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor
VL  - 184
IS  - 4
SP  - 1127
EP  - 1134
DO  - 10.1007/s00604-017-2115-5
ER  - 

@article{
author = "Mehmeti, Eda and Stanković, Dalibor M. and Chaiyo, Sudkate and Zavasnik, Janez and Zagar, Kristina and Kalcher, Kurt",
year = "2017",
abstract = "A reagentless third generation electrochemical glucose biosensor was fabricated based on wiring the template enzyme glucose oxidase (GOx) with graphene nanoribbons (GN) in order to create direct electron transfer between the co-factor (flavin adenine dinucleotide, FAD) and the electrode. The strategy involved: (i) isolation of the apo-enzyme by separating it from its co-enzyme; (ii) preparation of graphene nanoribbons (GN) by oxidative unzipping of multi-walled carbon nanotubes; (iii) adsorptive immobilization of GNs on the surface of a screen printed carbon electrode (SPCE); (iv) covalent attachment of FAD to the nanoribbons; (v) recombination of the apo-enzyme with the covalently bound FAD to the holoenzyme; and (vi) stabilization of the bio-layer with a thin membrane of Nafion. The biosensor (referred to as GN/FAD/apo-GOx/Nafion/SPCE) is operated at a potential of +0.475 V vs Ag/AgCl/{3 M KCl} in flow-injection mode with an oxygen-free phosphate buffer (pH 7.5) acting as a carrier. The signals are linearly proportional to the concentration of glucose in the range from 50 to 2000 mgai...L-1 with a detection limit of 20 mgai...L-1. The repeatability (10 measurements, at 1000 mgai...L-1 glucose) is +/- 1.4% and the reproducibility (5 sensors, 1000 mgai...L-1 glucose) is +/- 1.8%. The biosensor was applied to the determination of glucose in human serum.",
journal = "Microchimica Acta",
title = "Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor",
volume = "184",
number = "4",
pages = "1127-1134",
doi = "10.1007/s00604-017-2115-5"
}

Mehmeti, E., Stanković, D. M., Chaiyo, S., Zavasnik, J., Zagar, K.,& Kalcher, K.. (2017). Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor. in Microchimica Acta, 184(4), 1127-1134.
https://doi.org/10.1007/s00604-017-2115-5

Mehmeti E, Stanković DM, Chaiyo S, Zavasnik J, Zagar K, Kalcher K. Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor. in Microchimica Acta. 2017;184(4):1127-1134.
doi:10.1007/s00604-017-2115-5 .

Mehmeti, Eda, Stanković, Dalibor M., Chaiyo, Sudkate, Zavasnik, Janez, Zagar, Kristina, Kalcher, Kurt, "Wiring of glucose oxidase with graphene nanoribbons: an electrochemical third generation glucose biosensor" in Microchimica Acta, 184, no. 4 (2017):1127-1134,
https://doi.org/10.1007/s00604-017-2115-5 . .

TY  - JOUR
AU  - Mehmeti, Eda
AU  - Stanković, Dalibor M.
AU  - Kalcher, Kurt
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1892
AB  - In this work a new electrochemical method will be presented for the determination of enalapril in pharmaceutical tablets using unmodified screen printed electrode (SPE). The studies were done using amperommetric detection. Enalapril provides well defined, ovalshape oxidation peak at +1.05 V (vs. Ag/AgCl, 3.0 M KCl) in Britton-Robinson buffer solution (BRBS) at pH 5.0. After optimization of the experimental conditions, the influence of most common interferent compounds was tested. Under optimized experimental conditions, the signals were linearly proportional to the concentration of enalapril in the range from 2.5 to 90 mu M with a detection limit of 0.9 mu M. Repeatability of ten replicate measurements of 5 mu M enalapril was estimated to be 1.5%. Proposed method was successfully applied for the determination of the total amount of enalapril content in pharmaceutical preparations. Nevertheless, proposed method could be beneficial for the quick quantifications of enalapril in drugs using unmodified SPE electrode without any further treatment.
T2  - Analytical and Bioanalytical Electrochemistry
T1  - Determination of Enalapril in Pharmaceuticals using Electrochemical Sensing with Amperometric Detection
VL  - 9
IS  - 8
SP  - 1000
EP  - 1007
UR  - https://hdl.handle.net/21.15107/rcub_vinar_1892
ER  - 

@article{
author = "Mehmeti, Eda and Stanković, Dalibor M. and Kalcher, Kurt",
year = "2017",
abstract = "In this work a new electrochemical method will be presented for the determination of enalapril in pharmaceutical tablets using unmodified screen printed electrode (SPE). The studies were done using amperommetric detection. Enalapril provides well defined, ovalshape oxidation peak at +1.05 V (vs. Ag/AgCl, 3.0 M KCl) in Britton-Robinson buffer solution (BRBS) at pH 5.0. After optimization of the experimental conditions, the influence of most common interferent compounds was tested. Under optimized experimental conditions, the signals were linearly proportional to the concentration of enalapril in the range from 2.5 to 90 mu M with a detection limit of 0.9 mu M. Repeatability of ten replicate measurements of 5 mu M enalapril was estimated to be 1.5%. Proposed method was successfully applied for the determination of the total amount of enalapril content in pharmaceutical preparations. Nevertheless, proposed method could be beneficial for the quick quantifications of enalapril in drugs using unmodified SPE electrode without any further treatment.",
journal = "Analytical and Bioanalytical Electrochemistry",
title = "Determination of Enalapril in Pharmaceuticals using Electrochemical Sensing with Amperometric Detection",
volume = "9",
number = "8",
pages = "1000-1007",
url = "https://hdl.handle.net/21.15107/rcub_vinar_1892"
}

Mehmeti, E., Stanković, D. M.,& Kalcher, K.. (2017). Determination of Enalapril in Pharmaceuticals using Electrochemical Sensing with Amperometric Detection. in Analytical and Bioanalytical Electrochemistry, 9(8), 1000-1007.
https://hdl.handle.net/21.15107/rcub_vinar_1892

Mehmeti E, Stanković DM, Kalcher K. Determination of Enalapril in Pharmaceuticals using Electrochemical Sensing with Amperometric Detection. in Analytical and Bioanalytical Electrochemistry. 2017;9(8):1000-1007.
https://hdl.handle.net/21.15107/rcub_vinar_1892 .

Mehmeti, Eda, Stanković, Dalibor M., Kalcher, Kurt, "Determination of Enalapril in Pharmaceuticals using Electrochemical Sensing with Amperometric Detection" in Analytical and Bioanalytical Electrochemistry, 9, no. 8 (2017):1000-1007,
https://hdl.handle.net/21.15107/rcub_vinar_1892 .

TY  - JOUR
AU  - Mehmeti, Eda
AU  - Stanković, Dalibor M.
AU  - Ortner, Astrid
AU  - Zavasnik, Janez
AU  - Kalcher, Kurt
PY  - 2017
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/1763
AB  - A boron-doped diamond electrode was used as an electrochemical sensor for the determination of phlorizin (aka phloridzin, phlorrhizin) using square wave voltammetry (SWV). Phlorizin (Phl) exhibited a well-defined oxidation peak at +0.9 V (versus Ag/AgCl electrode 3 M KCl) in solutions with a pH value of 6.0. Parameters such as pH value and scan rate were optimized for cyclic voltammetry as well as amplitude and frequency for SWV. The sensor gave excellent response with a wide linear dynamic range for concentrations of phlorizin from 3 to 100 mu M with a detection limit of 0.23 mu M and a good repeatability (+/- 0.9%, n = 7 measurements, c = 10 mu M). The effect of interferences by most common compounds was tested, and the method was successfully applied to the determination of the title compound in apple root extracts and urine samples with satisfactory recovery.
T2  - Food Analytical Methods
T1  - Highly Selective Electrochemical Determination of Phlorizin Using Square Wave Voltammetry at a Boron-Doped Diamond Electrode
VL  - 10
IS  - 11
SP  - 3747
EP  - 3752
DO  - 10.1007/s12161-017-0935-x
ER  - 

@article{
author = "Mehmeti, Eda and Stanković, Dalibor M. and Ortner, Astrid and Zavasnik, Janez and Kalcher, Kurt",
year = "2017",
abstract = "A boron-doped diamond electrode was used as an electrochemical sensor for the determination of phlorizin (aka phloridzin, phlorrhizin) using square wave voltammetry (SWV). Phlorizin (Phl) exhibited a well-defined oxidation peak at +0.9 V (versus Ag/AgCl electrode 3 M KCl) in solutions with a pH value of 6.0. Parameters such as pH value and scan rate were optimized for cyclic voltammetry as well as amplitude and frequency for SWV. The sensor gave excellent response with a wide linear dynamic range for concentrations of phlorizin from 3 to 100 mu M with a detection limit of 0.23 mu M and a good repeatability (+/- 0.9%, n = 7 measurements, c = 10 mu M). The effect of interferences by most common compounds was tested, and the method was successfully applied to the determination of the title compound in apple root extracts and urine samples with satisfactory recovery.",
journal = "Food Analytical Methods",
title = "Highly Selective Electrochemical Determination of Phlorizin Using Square Wave Voltammetry at a Boron-Doped Diamond Electrode",
volume = "10",
number = "11",
pages = "3747-3752",
doi = "10.1007/s12161-017-0935-x"
}

Mehmeti, E., Stanković, D. M., Ortner, A., Zavasnik, J.,& Kalcher, K.. (2017). Highly Selective Electrochemical Determination of Phlorizin Using Square Wave Voltammetry at a Boron-Doped Diamond Electrode. in Food Analytical Methods, 10(11), 3747-3752.
https://doi.org/10.1007/s12161-017-0935-x

Mehmeti E, Stanković DM, Ortner A, Zavasnik J, Kalcher K. Highly Selective Electrochemical Determination of Phlorizin Using Square Wave Voltammetry at a Boron-Doped Diamond Electrode. in Food Analytical Methods. 2017;10(11):3747-3752.
doi:10.1007/s12161-017-0935-x .

Mehmeti, Eda, Stanković, Dalibor M., Ortner, Astrid, Zavasnik, Janez, Kalcher, Kurt, "Highly Selective Electrochemical Determination of Phlorizin Using Square Wave Voltammetry at a Boron-Doped Diamond Electrode" in Food Analytical Methods, 10, no. 11 (2017):3747-3752,
https://doi.org/10.1007/s12161-017-0935-x . .