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Voltametric Determination of 4-Nitrophenol at a Bismuth Film Electrode
Hausner, Jiří ; Barek, Jiří (advisor) ; Dejmková, Hana (referee)
This Bachelor Thesis is focussed on the study of electrochemical behaviour of 4-nitrophenol (4-NP) and the search for optimal conditions for its voltammetric determination at a bismuth film-modified gold electrode (BiF-AuE). Voltammetric behaviour of 4-NP (c = 1×10-4 mol L-1 ) was investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) in dependence on the pH of the medium used (Britton-Robinson buffers). For both techniques, Britton-Robinson buffer of pH 7.0 was chosen as the optimum medium. Repeatability of the determination of 4-NP (c = 1×10-4 mol L-1 ) was 0.6 % and 0.9 % for DCV and DPV, respectively. Calibration dependences of 4-NP were measured in the concentration range from 1×10-6 to 1×10-4 mol L-1 under the optimum conditions. Attained limits of quantification (LQs) were 7.6×10-7 mol L-1 and 1.5×10-6 mol L-1 for DCV and DPV, respectively. The applicability of the newly developed voltammetric methods for the determination of 4-NP was verified on model samples of drinking water with LQ 7.5×10-6 mol L-1 for DCV at the BiF-AuE and 1.4×10-6 mol L-1 for DPV at the BiF-AuE.
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Voltammetric Determination of Herbicide Aclonifen Using Mercury Electrodes
Murcková, Klára ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
Presented Diploma Thesis is focused on electroanalytical determination of the herbicide Aclonifen, which belongs to a group of herbicides derived from diphenylether. These herbicides are used due to their effects - inhibition of protoporfyrinogen oxidase synthesis and also inhibition of biosynthesis of carotenoids. Due to its widespread use in agricultural, toxical effects on humans and because of its negative impacts particularly on aquatic ecosystems there is a need for methods capable of determining the presence of Aclonifen in the environment to monitor its ecological impacts. Optimal conditions for the determination of Aclonifen have been investigated in BR buffer - methanolic solution and in BR buffer. Electrochemical behavior of the substance has been studied using direct current voltammetry (DCV), differential pulse voltammetry (DPP) and adsorptive stripping voltammetry (AdSV) on the hanging mercury drop electrode (HMDE) and by using TAST polarography and differential pulse polarography (DPP) on the dropping mercury electrode (DME). UV/VIS spectrophotometric detection was used for comparison to electrochemical detection. Used wavelengths were 308 nm and 388 nm. For electrochemical determination of Aclonifen the above mentioned techniques were used and following results were obtained: DCV...
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Voltammetric Determination of 5-Nitrobenzimidazole Using Non-Traditional Electrode Materials
Chládková, Barbora ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
5 Abstract This Diploma Thesis is targeted on the determination of 5-nitrobenzimidazole (5-NBIA) using following techniques: DC voltammetry (DCV) and differential pulse voltammetry (DPV). As working electrodes, a silver amalgam paste electrode (AgA-PE), which was constructed for this determination in the form of a new prototype, a bismuth film electrode (BiFE), at which the optimum conditions for the deposition of the bismuth film at a suitable substrate (glassy carbon electrode and gold electrode were tested for this purpose) were initially optimized, and a glassy carbon electrode (GCE) were used. The optimum conditions for the voltammetric determination of 5-NBIA at the AgA-PE (in a medium of Britton-Robinson buffer (BR-buffer) of pH 7.0 for both DCV and DPV), at the BiFE with gold substrate (BR-buffer of pH 9.0 for both DCV and DPV; the film was deposited "ex situ" in a stirred plating solution (1000 mg L-1 Bi(III) solution in 0.1 mol L-1 acetate buffer of pH 4.5) for 300 s), and at the GCE (BR-buffer of pH 5,0 for both DCV and DPV). Under these conditions, calibration dependences were measured in the concentration ranges of 0.1 - 100 µmol L-1 (pro DCV a DPV na AgA-PE) and 1 - 100 µmol L-1 (pro DCV a DPV na BiFE a GCE), and the limits of quantification (LQs) were calculated for particular methods: LQ ≈...
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Voltammetric Determination of Genotoxic Nitrobiphenyls
Horáková, Eva ; Vyskočil, Vlastimil (advisor) ; Navrátil, Tomáš (referee)
The presented diploma thesis is devoted to study of determination of 4-nitrobiphenyl (4-NBP) in model river water by DC voltammetry (DCV) and differential pulse voltammetry (DPV) at m-AgSAE (diploma thesis relates to bachelor thesis, in it DCV and DPV methods for determination of 4-NBP in deionized water were developed). Limit of determination (LOD) is 2·10-7 mol·l-1 by DCV and 4·10-7 mol·l-1 by DPV. The adsorptive stripping DPV (AdSDPV) technique was tested to archive lower LOD the AdSDPV, optimal conditions were not found. Electrochemical behavior of 2-nitrobiphenyl (2-NBP) at m-AgSAE was studied. Optimal conditions for its determination by both techniques DCV and DPV were found in methanol-0,01 mol·l-1 LiOH (1:9) and in this medium peak current dependence in 1·10-7 mol·l-1 to 1·10-4 mol·l-1 2-NBP (LOD ≈ 2·10-7 mol·l-1 by DCV and 1·10-7 mol·l-1 by DPV) concentration range was measured. Developed methods were successfully tested for determination of 2-NBP in drinking and river water samples. For both mediums obtained LODs were 2·10-7 mol·l-1 by DCV and 1·10-7 mol·l-1 by DPV. AdSDPV technique was unsuccessfully tested to achieve lower LOD. Optimal conditions for simultaneous determination of 4-NBP and 2-NBP by DPV technique at m-AgSAE were found: methanol-0,25 mol·l-1 acetate buffer (pH = 6,0) 3:7....
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Voltammetric Determination of Genotoxic 6-Nitrochrysene at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Šmídková, Monika ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
This Bachelor Thesis is devoted to the study of electrochemical behavior of 6-nitrochrysene (6-NCH) and to the finding of the optimum conditions for its determination using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE). For measuring the concentration dependences of 6-NCH, the optimum medium methanol - BR buffer pH 9.0 (1:1) and the proper regeneration potentials Ereg,1 = 0 mV, Ereg,2 = -600 mV have been chosen for DCV at m-AgSAE and the medium methanol - BR buffer pH 10.0 (1:1) and the proper regeneration potentials Ereg,1 = 0 mV, Ereg,2 = -750 mV have been chosen for DPV at m-AgSAE. The concentration dependence was found to be linear only for the lowest concentration range of 10-7 mol·l-1 . In the concentration range of 10-6 mol·l-1 , the concentration dependences observed were polynomial. This result indicates a possible adsorption of 6-NCH on the surface of working electrode. Reached limits of quantification (LQ) were 1·10-7 mol·l-1 for DCV at m-AgSAE and 5·10-8 mol·l-1 for DPV at m-AgSAE. For comparison, the concentration dependence of 6-NCH was measured in methanol using UV-VIS spectrophotometry. Reached LQ ~ 1·10-7 mol·l-1 is comparable with LQs reached using DCV and DPV techniques.
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Voltammetric determination of drugs doxycycline and dimenhydrinate using carbon film electrode
Humpolíková, Jiřina ; Fischer, Jan (advisor) ; Dejmková, Hana (referee)
This bachelor's thesis concerns the determination of doxycycline (DX) and dimenhydrinate (DMH) by the methods DC voltammetry (DCV) and differential pulse voltammetry (DPV) on a carbon film electrode (CFE). The optimum conditions for voltammetric determination of DX and DMH were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. The media of BR-buffer pH 12.0 was chosen as optimum for DCV and DPV determination of DX at CFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of DX from 20 µmol·l-1 to 100 µmol·l-1 with LOQ 15,4 µmol·l-1 for DCV and 15,2 µmol·l-1 for DPV. DX was determined in drug using DCV under optimized conditions and for comparison of used voltammetric method DX in drug was determined also using UV-VIS spectrophotometry with consistent results. The optimum medium of BR buffer pH 3.0 was chosen for determination of DMH by DCV and pH 2.0 for DPV. The calibration range 2,0 - 10,0 µmol·l-1 of DMH was received using DCV and 0,2 - 1,0 µmol·l-1 of DMH was recevied using DPV at CFE with reached LOQ 0,08 µmol·l-1 for DCV and 0,02 µmol·l-1 for DPV. DMH was determined in comertional drugs using DCV on founded conditions. The stability of stock solution...
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Voltammetric Determination of 4-Nitrophenol at a Large-Surface Carbon Film Electrode
Šmejkalová, Hana ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
The aim of presented Bachelor Thesis was to study an electrochemical behavior of 4-nitrophenol (4-NP) resulting in the founding of optimum conditions for its determination at newly prepared large-surface carbon film electrode (ls-CFE) using DC voltametry (DCV) and differential pulse voltammetry (DPV). Voltammetic behavior of 4-NP was investigated in dependence on the pH of the medium (realized using Britton-Robinson buffer). As optimum pH values for voltammetric determination of 4-NP at ls-CFE in cathodic potentials region, the pH values 6.0 (for DCV) and 7.0 (for DPV) were chosen. The determinations of 4-NP at ls-CFE (at a concentration of the analyte of 1·10-4 mol/l) showed a good repeatability for both voltammetric techniques used (2.2 % for DCV and 0.4 % for DPV). Therefore, the possibility of an electrochemical regeneration of the electrode surface has not been further investigated. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 2·10-6 to 1·10-4 mol/l, with limits of quantification (LQ) of 2.3·10-6 mol/l (for DCV at ls-CFE) and 1.8·10-6 mol/l (for DPV at ls-CFE). The applicability of the newly developed methods of the determination of 4-NP was verified on the model samples of drinking water, with LQ of 1.0·10-6 mol/l (for DCV at...
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Voltammetric Study of the Interaction of Genotoxic 2-Nitrofluorene with DNA at a Hanging Mercury Drop Electrode
Krejčová, Zuzana ; Vyskočil, Vlastimil (advisor) ; Nesměrák, Karel (referee)
In this Diploma Thesis, an interaction of genotoxic environmental pollutant 2-nitrofluorene with a double-stranded calf thymus DNA has been studied using a hanging mercury drop electrode (HMDE) as an electrochemical sensor. Two types of DNA damage were investigated and electrochemically detected (using cyclic voltammetry and differential pulse voltammetry): (i) The DNA damage caused by the direct interaction with 2-nitrofluorene and (ii) the DNA damage caused by short-lived radicals generated by the electrochemical reduction of the nitro group in 2-nitrofluorene. For the study of direct interaction, HMDE was modified by DNA and the interaction of DNA with 2-nitrofluorene was studied, after their incubation, right at the HMDE surface (adsorptive transfer stripping technique) or the DNA was preincubated with 2-nitrofluorene and, subsequently, the interaction was studied voltammetrically (DNA titration technique). Using both detection techniques, the formation of DNA - 2-nitrofluorene complex was observed and the mutual interaction was interpreted as an intercalation between the DNA base pairs, although such interaction was not clearly confirmed by UV-visible absorption spectroscopy. An electrostatic binding of 2-nitrofluorene on DNA sugar-phosphate backbone was partially formed at low concentrations of...
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Voltammetric Determination of Dinitronaphthalenes Using Single Crystal Silver Amalgam Electrode
Tvrdíková, Jana ; Barek, Jiří (advisor) ; Dejmková, Hana (referee)
Voltammetric methods for determination of 1,3-dinitronaphthalene (1,3-DNN), 1,5-dinitronaphthalene (1,5-DNN) and 1,8-dinitronaphthalene (1,8-DNN) using DC voltammetry (DCV) and differential pulse voltammetry (DPV) at novel single crystal silver amalgam electrode (CAgAE) were developed in this work. Developed methods may be used for determination of 1,3-DNN within a concentration range 2 - 10 μmol.L-1 with LoQ 2 μmol.L-1 using DCV and 1 - 100 μmol.L-1 with LoQ 1 μmol.L-1 by DPV; 1,5-DNN wihin a concentration range 2 - 10 μmol.L-1 with LoQ 2 μmol.L-1 using DCV and 1 - 10 μmol.L-1 with LoQ 1 μmol.L-1 by DPV and 1,8-DNN within a concentration range 2 - 10 μmol.L-1 with LoQ 2 μmol.L-1 using DCV and 0,3 - 1 μmol.L-1 with LoQ 0,3 μmol.L-1 by DPV. An attepmt to decrease LoQ by adsorptive stripping differential pulse voltammetry was not successful. Process of electrochemical reduction of selected dinitronaphthalenes on the working electrode was also studied by cyclic voltammetry. This work verified the use of CAgAE as alternative electrode material to mercury electrodes for determination of electrochemically reducible organic compounds in aqueous-methanolic media. Small dimensions of the CAgAE are the main advantages which predetermine its use in voltammetric microvolume batch analysis and amperometric detection in...
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Voltammetric and amperometric detection of genotoxic pyrene derivatives at boron-doped diamond film electrode
Yosypchuk, Oksana ; Barek, Jiří (advisor) ; Nesměrák, Karel (referee)
This thesis is concentrated on the optimization of conditions for determination of genotoxic environmental pollutants whitch belong to derivatives of polycyclic aromatic hydrocarbons − 1-nitropyrene (1-NP), 1-aminopyrene (1-AP) and 1-hydroxypyrene (1-HP). All three compounds were determined by differential pulse voltammetry (DPV) at boron-doped diamond film electrode in water-methanolic solutions. Further, 1-AP and 1-HP were determined in a model sample of urine. For this purpose, effective separative techniques such as solid phase extraction and high performance liquid chromatography with reverse phase and amperometric detection at above mentioned type of electrode were used. Limits of detection of all tested compounds in water-methanolic solutions are 9⋅10−8 −3⋅10−7 mol dm−3 using DPV and 1⋅10−8 mol dm−3 for 1-HP and 1-AP in model sample of urine determined by HPLC with amperometric detection.
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