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...

The main objective of this Diploma Thesis is studying the possibility of detection of nitro derivatives of aromatic hydrocarbons by using chemically modified working electrodes in electrochemical analysis. Compounds analyzed in this work were 1-nitronaphthalene and 6- nitrochrysene - these compounds were chosen on previous experience with surface modified working electrodes (the chemical/physical properties of these substances). All the analyses were performed by using differential pulse voltammetry (DPV) on hanging mercury drop electrode (HMDE) in classic three-electrode system. The original premise of chemical modification of electrode surface is the change of its selectivity towards different compounds - meaning the change of the electrochemical response. The modification agent used in this thesis is 1-octanethiol. Its thiol group offers great potential of strong interaction with the metal surface of the mercury electrode. Voltammetric responses of both compounds were recorded in acidic, neutral and basic solutions (pH=2, pH=7, pH=12) including the responses when the electrode surface was modified. Next objective was the optimization of the modification procedure itself (transferring of the mercury drop from one media to another without damaging or tearing it off from the capillary orifice)....

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.

Объектами исследования служили лечебный препарат «Эндофальк» и товарный уротропина от ПАО «Метафракс». Цель работы: разработка вольтамперометрической методики количественного определения формальдегида с использованием толстопленочного углеродсодержащего электрода, модифицированного пленкой висмута (ТУЭ/Bi), в объектах фармации на примере уротропина и лекарственного препарата, содержащего в качестве основного вещества субстанцию «Макрогол 3350». Формальдегид (ФМ) относится к высоко опасным веществам с канцерогенным действием. Простые и чувствительные методы определения формальдегида необходимы для его контроля в объектах окружающей среды, питьевой воде, пищевых продуктах, товарах бытового назначения, фармпрепаратах. Электроаналитические методы с использованием индикаторных электродов, модифицированных различными металлами (Pd, Pt, Au, Ni Hg, Cu, Ag), считаются хорошей альтернативой спектральным, хемилюминесцентным и хроматографическим методам анализа для обнаружения следов ФМ из-за их высокой чувствительности, селективности, простоты и низкой стоимости оборудования, возможности проведения измерений в режиме реального времени. В работе впервые изучена возможность использования нетоксичного Bi/ТУЭ для определения ФМ. Для перевода гидратированной формы ФМ в его электрохимически активное производное использовали известный прием образования формальдегид гидразона (ФАГ) в присутствии сернокислого гидразина на фоне фосфатного буфера. Ток восстановления ФМ (АС) достигает максимальных значений при рН буферного раствора 5,2 ± 0,1 в присутствии 0,09– 0,15 М сернокислого гидразина на пленке висмута, осажденной предварительно в течение 8 - 12 мин при потенциале электролиза (-1,0) В. Установлено, что величина АС ФМ не зависит от времени накопления при потенциале (–0,5) В, при котором не происходят редокс - процессы в исследуемой системе, в течение 1 – 30 с. Разработаны методики количественного определения формальдегида в объектах фармации на примере ЛП «Эндофальк» и товарного уротропина от ПАО «Метафракс». Правильность полученных результатов подтверждена сравнением с результатами независимых методов анализа, прописанных в ФС РФ XIV издания на субстанции уротропина и «Макрогола 3350». / The objects of research were the medicinal product “Endofalk” and marketed urotropin from PJSC “Metafrax”. The mail goal of the research was to develope of a voltammetric method for quantitative determination of formaldehyde using a thick-film carbon-containing electrode modified with a bismuth film (TUE / Bi) in pharmacological objects on the example of urotropin and a drug similar to the substance “Macrogol 3350”. Formaldehyde (FM) is a highly hazardous substance with a carcinogenic effect. Simple and sensitive methods for the determination of formaldehyde are necessary for its control in environmental objects, drinking water, food products, household goods, pharmaceuticals. Electroanalytical methods using indicator electrodes modified with various metals (Pd, Pt, Au, Ni Hg, Cu, Ag) are considered to be a good alternative to spectral, chemiluminescent and chromatographic analysis methods for detecting traces of FM due to their high sensitivity, selectivity, simplicity and low cost of equipment, the ability to take measurements in real time. The possibility of using non-toxic Bi / TUE for the determination of FM was first studied in this work. To transfer the hydrated form of FM to its electrochemically active derivative, the well-known method for the formation of formaldehyde hydrazone (FAG) in the presence of hydrazine sulfate in the background of phosphate buffer was used. A higher current was obtained in buffer solution with value of pH 5.2 ± 0.1 and in a solution of 0.09–0.15 M hydrazine sulfate on a bismuth film pre-deposited for 8–12 min at an electrolysis potential of (-1 , 0). It was established that the value of AS FM does not depend on the accumulation time at a potential of (–0.5) V, at which no redox processes in the system for 1–30 s under study are observed. Methods have been developed for the quantitative determination of formaldehyde in pharmacological objects on the example of medicinal preparation “Endofalk” and urotropin from PJSC “Metafrax”. The correctness of the obtained results is confirmed by comparison with the results of independent analysis methods prescribed in the Federal Assembly of the Russian Federation of the XIV edition on the substances of urotropin and “Macrogol 3350”.

This Diploma Thesis is focused on study of electrochemical behavior of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (picric acid) on finding the optimum conditions for their determination using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) in the solution of Britton-Robinson (BR) and on finding of the limit of quantification (LQ) for these substances. Practical applicability of the newly developed methods was verified on direct determination of TNT and picric acid in model samples of drinking and river water. Moreover, the electrochemical behaviors of TNT and picric acid was studied using cyclic voltammetry (CV). Optimum medium for the determination of TNT at m-AgSAE was: methanol-BR buffer pH 4.0 (1:9). Upon the DCV it is proper to apply regeneration potentials Ereg,1= 0 mV and Ereg,2= -1100 mV and upon the DPV was apply regeneration potentials Ereg,1= 0 mV and Ereg,2= -600 mV were applied. The concentration dependence of the peak current was found to be linear for both techniques over the concentration range of 1·10-6 -1·10-4 mol/l with LQ of 0.54 µmol/l (for DCV) and 0.46 µmol/l (for DPV). The method developed for the determination of TNT were verified on the model samples of drinking...

The aim of presented Diploma Thesis was to study an electrochemical behavior of nitroimidazole drugs metronidazole and ornidazole and to find optimal conditions for their voltammetric determination at a mercury meniscus modified silver solid amalgam electrode using DC voltammetry (DCV) and differential pulse voltammetry (DPV). Voltammetric behavior of selected drugs was investigated in dependence on the pH of the medium used (realized using a Britton-Robinson buffer (BR buffer)) and a mechanism of the reduction of both drugs was investigated using cyclic voltammetry (CV). The optimum medium for voltammetric determination of studied nitroimidazole drugs at the m-AgSAE in a region of cathodic potentials was found to be the BR buffer of pH 8.0. Then, the concentration dependences were measured in this optimum medium in the concentration range from 2·10-7 mol/L to 1·10-4 mol/L. The limits of quantification (LQs) for both metronidazole and ornidazole were found in the concentration order of 10-7 mol/L by using DCV and DPV at the m-AgSAE. The applicability of the newly developed voltammetric methods of the determination of nitroimidazole drugs was verified on the model samples of drinking and river water, with LQ ≈ 2·10-7 mol/L for both DC voltammetry and differential pulse voltammetry at the m-AgSAE....

Diploma thesis deals of nanostructured surfaces, nanoparticles and electrochemical characterization methods such as cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The aim of this thesis is a theoretical research issues of production and characterization nanostructured modified electrodes. The practical part is the production of biomodified nanostructured electrodes by anodi- zation W/Al layers with galvanic deposition of gold or deposition of mercury, a modifi- cation of the electrodes by 11-mercaptoundecanoic acid and by bovine serum albumin (BSA). The thesis includes SEM images of nanostructured electrodes contact angle mea- surements of these electrodes and form an electrical circuit with subsequent simulation waveforms.

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 ≈...

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...

9 Abstract In this Ph.D. thesis possibilities of using our proposed potential programs for a multiple-pulse amperometry and a fast scan differential pulse voltammetry in combination with flow systems are presented. The development of new sensitive amperometric and voltammetric methods for the determination of oxidisable biologically active organic compounds is another aim of this work. In the first part of the work, the flow injection system and multiple-pulse amperometric detection were employed to develop and optimize a simple, low-cost, and rapid method for the simultaneous determination of natural and synthetic antioxidants. This technique involves the application of an appropriate potential waveform consisting of a suitable sequence of pulses on a single working electrode, thus allowing distinguish the analytes in a mixture with no need of separation. Conditions for the determination of antioxidants and modelling of the potential program were tested and studied, respectively. Second part of the work describes and characterizes the application of the fast scan differential pulse voltammetry (FSDPV) in combination with the flow systems. FSDPV is the electroanalytical technique that use high scan rate to record voltammograms within several milliseconds and ensures high temporal resolution. This technique...