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...

This diploma thesis is focused on the determination of chloramphenicol by differential pulse voltammetry (DPV), DC voltammetry (DCV), cyclic voltammetry (CV) and adsorptive stripping voltammetry (AdSV) on a meniscus modified silver solid amalgame electrode (m- AgSAE). For the determination of chloramphenicol the optimum conditions were found and under these conditions concentration dependences were measured and then limits of quantification were determined. The influence of pH of BR buffer was tested. For determination of chloramphenicol by DCV pH 7 was chosen as an optimum background and pH 8 was chosen as an optimmum for DPV determination. Under these conditions linear dependences were obtained in the concentration range of 1·10-6 - 1·10-4 mol·l-1 . The limit of detection of chloramphenicol by DCV was 2.3·10-6 mol·l-1 . The limit of detection of chloramphenicol by DPV was 2.1·10-6 mol·l-1 in distilled water, 2.9·10-6 mol·l-1 in river water and 4.2·10-6 mol·l-1 in drinking water. Electrochemical behavior of chloramphenicol was studied by cyclic voltammetry in BR buffer with pH 2, 6, 8, 12 and then mechanism of reduction of chloramphenicol was propose based on available literature. Chloramphenicol was determined in drug Spersadex by DPV in BR buffer with pH 8. The optimal conditions for determining...

This Diploma Thesis is focused on investigation of the voltammetric behavior of the explosive penthrite (pentaerythritol tetranitrate) (PETN) and on searching for optimum conditions for its determination using differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE) (this part of the Diploma Thesis follows the topic investigated in the author's Bachelor Thesis; in this Diploma Thesis, the results of the Bachelor thesis are applied to the determination of PETN in environmental matrices) and at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) and on investigation of voltammetric behavior in real samples (deionized, drinking, and river water). For investigating the behavior of PETN in aqueous-methanolic media on the m-AgSAE, mixtures of Britton-Robinson buffers (BR-buffers) and methanol in various volume ratios were used. In non-aqueous media, methanolic solutions of tetramethylammonium bromide (TMAB), tetrabutylammonium iodide (TBAI), and tetrabutylammonium chloride (TBAC) were used as supporting electrolytes. Firstly, the influence of pH (in the range of 2 - 13) and methanol content (10 - 90 vol. %) on voltammetric responses of PETN was studied. The best response was obtained at each of those pH values at the volume ratio of BR-buffer - methanol of 1:9 or...

of the Diploma Thesis In this Diploma Thesis, the electrochemical behavior of 4-nitrophenol (4-NP) was studied at a newly prepared large-surface carbon film electrode (ls-CFE) using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) with the aim to develop sensitive analytical methods for its determination. Voltammetric behavior of 4-NP was investigated in the region of anodic potentials, in dependence on the pH of the medium used (realized using Britton-Robinson buffer). The optimum pH values for the determination of 4-NP were chosen as follows: pH 3.0 (for DCV) and pH 7.0 (for DPV). During anodic oxidation of 4-NP on the ls-CFE at the concentration of the analyte of 1·10-4 mol/l, the passivation of the electrode surface occurred. Thus, it was decided to record series of measurements always at a new carbon film. Using the sample of 4-NP (at the concentration of 1·10-4 mol/l), the repeatability of the application of individual carbon films was tested, with obtained RSD values of 3.7% and 3.6% for DCV and DPV, respectively. Under optimum conditions, the calibration dependences of 4-NP were measured in the concentration range from 1·10-6 to 1·10-4 mol/l, with the limits of quantification (LQs) of 1.5·10-6 mol/l (for DCV at the ls-CFE) and 4.6·10-7 mol/l (for DPV at the...

This master's thesis is focused on the determination of 6-thioguanine (6-T) by DC voltammetry (DCV), differential pulse voltammetry (DPV) and flow injection analysis with electrochemical detection (FIA-ED) on a boron doped diamond electrode (BDDFE). The optimum conditions for determination of 6-T were found and under these conditions, concentration dependences were measured and the limits of quantification (LOQ) were calculated for each method. Medium of 60% methanol and phosphate buffer (PB) pH 2,0 was chosen as optimum for DCV and DPV determination of 6-T at BDDFE. For both DCV and DPV, the linear concentration dependences were obtained in concentration ranges of 6-T from 2 µmol·l-1 to 10 µmol·l-1 with LOQ 0,9 µmol·l-1 for DCV and 1,5 µmol·l-1 for DPV. Lower LOQ was achieved in PB pH 2,0, where LOQ was 0,6 µmol·l-1 for both DCV and DPV, but the problem was lower repeatability. In PB pH 2 6-T was determined by DCV in drinking and river water with LOQ 1,3 µmol·l-1 in both drinking and river water. The possibility of solid phase extraction was investigated as a method for preliminary separation of 6-T from urine. For FIA under optimized conditions (polarization potential 1300 mV, flow rate 5 ml·min1 and sample volume 50 µl) the linear concentrations dependences were obtained in concentration ranges...

The submitted work deals with the application of voltammetric determination of Fomesafen using non-traditional mercury meniscus modified silver solid amalgam electrode on model samples of Fomesafen in real aqueous matrices of drinking and river water. This method of measurement has been developed and optimized in my bachelor thesis, which the diploma thesis is related to. Fomesafen belongs to a group of herbicides used on a mass scale in the late 20th century in the USA and in many countries around the world still used even today. Among its side effects according to the EPA include, among others, potential carcinogenicity to humans and confirmed carcinogenicity to some mammals (such as rats) which led to a legislative regulation on its use in many countries around the world including the USA, the European Union and many others. Silver solid amalgam electrode has been developed with the intention to limit the use of mercury in accordance with new legislation of the European Union and the concept of green analytical chemistry. Despite the low levels of mercury mainly bound in the form of virtually harmless silver amalgam electrode retains very similar electrochemical properties with proven mercury electrodes. As part of the thesis, direct determination of a number of partial extraction of Fomesafen...

Presented Diploma Thesis deals with the study of electrochemical behavior of 5-nitroimidazole (5-NI), with the search for optimal conditions for its determination using techniques of DC voltammetry (DCV) and differential pulse voltammetry (DPV) at a mercury meniscus modified silver solid amalgam electrode (m-AgSAE) and at a boron-doped diamond film electrode (BDDFE), and with the comparison of reached limits of quantification (LQs). The optimal conditions found for measuring calibration dependences of 5-NI at the m-AgSAE in deionized water were as follows: Britton-Robinson buffer of pH 7.0 and 10.0 for DCV and DPV, respectively. At both thechniques, it is advisable to use an electrochemical regeneration of the electrode surface by the application of a couple of regeneration potentials Ereg,1 = 0 mV and Ereg,2 = −800 mV. The calibration dependences were measured in the concentration range from 1·10−6 to 1·10−4 mol·l−1 , with the LQs of 1.0·10−6 mol·l−1 for DCV at the m-AgSAE and 1.5·10−6 mol·l−1 for DPV at the m-AgSAE. The concentration dependences of 5-NI at the BDDFE were measured using the DCV technique in the BR buffer of pH 3.0. For the DPV technique, the optimal medium seemed to be the BR buffer of pH 2.0, however, because of the presence of an interfering peak in the supporting electrolyte,...

Differential pulse voltammetry (DPV) was used for developing a method for the determination of phenothiazine derivatives, namely chlorpromazine (CHP) and levomepromazine (LMP), using a glassy carbon electrode (GCE) and a graphite electrode, both with a 2 mm disc diameter. Comparison of quantification limits (LQ) for both substances on both electrodes was performed. After optimizing and processing the results, the optimal conditions for measuring calibrations were as follows: Britton- Robinson (BR) buffer at pH 4.0. Calibration dependences were measured inthe concentration range from 1·10-7 to 1·10-4 mol·dm-3 . There was no need for electrochemical electrode regeneration or matrix pretreatment. The results showed higher measurement sensitivity for CHP, and the graphite electrode also showed higher sensitivity. Although there were measured lower concentrations with the graphite electrode in comparison to the GCE, because of the low repeatability of the measurements in the lower concentration range 1-10·10-7 mol·dm-3 , the LQ is comparable to the results reached on the GCE. Besides to the BR buffer, measurements in other matrices (drinking water and river water) were also made. The following LQ values were achieved: 1.0·10-6 mol·dm-3 (in BR buffer), 1.1·10-6 -1.4·10-6 mol·dm-3 (in drinking water) and...

Made available in DSpace on 2014-12-17T15:42:11Z (GMT). No. of bitstreams: 1 NathaliaCVN_DISSERT.pdf: 2020842 bytes, checksum: efcd9ca5e5cfd7d63412f72c80546c39 (MD5) Previous issue date: 2013-07-31 / In this paper, the technique of differential pulse voltammetry (DPV) has been studied for monitoring the concentration of oxalic acid (OA) during their electrochemical oxidation (EO) in acidic medium using platinum anode supported on titanium (Ti / Pt). The DPV was standardized and optimized using a glassy carbon electrode modified with cysteine. The modification with cysteine was developed electrochemically, forming a polymeric film on the surface of the glassy carbon electrode. The formation of the polymer film was confirmed by analysis of scanning electron microscope and atomic force microscope, confirming the modification of the electrode. The electrochemical degradation was developed using different current densities 10, 20 30 and 40 mA cm -2 electrode with Ti / Pt observing the degradation of oxalic acid, and monitored using the method of KMnO4 titration. However, the analyzes with DPV showed the same behavior elimination of oxalic acid titration. Compared with the titration method classical observed and DPV could be a good fit, confidence limits of detection and confirming the applicability of the technique electroanalytical for monitoring the degradation of oxalic acid / No presente trabalho, a t?cnica de voltametria de pulso diferencial (DPV) foi estudada para o monitoramento da concentra??o de ?cido ox?lico (OA) durante a sua oxida??o eletroqu?mica (EO) em meio ?cido utilizando o ?nodo de platina suportada em tit?nio (Ti/Pt). A t?cnica de DPV foi padronizada e otimizada usando um eletrodo de carbono v?treo modificado com ciste?na. A modifica??o com ciste?na foi desenvolvida eletroquimicamente, formando um filme polim?rico na superf?cie do eletrodo de carbono v?treo. A forma??o do filme polim?rico foi confirmada por an?lise de Microsc?pio Eletr?nico de Varredura e Microsc?pio de For?a At?mica, confirmando a modifica??o na superf?cie do eletrodo. A degrada??o eletroqu?mica foi desenvolvida usando diferentes densidades de corrente, 10, 20 e 30 mA cm-? com eletrodo de Ti/Pt, observando a degrada??o do ?cido ox?lico, sendo monitorado empregando a metodologia de titula??o com KmnO4. No entanto, as an?lises com DPV mostraram o mesmo comportamento de elimina??o do acido ox?lico, observado com a titula??o. Comparado com o m?todo de titula??o cl?ssica e DPV conseguiu-se um bom ajuste, intervalos de confian?a e limites de detec??o confirmando a aplicabilidade da t?cnica eletroanal?tica para o monitoramento da degrada??o de ?cido ox?lico

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....