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Silver Amalgam Electrodes in Electroanalysis of Selected Agrochemicals
Daňhel, Aleš ; Barek, Jiří (advisor) ; Vytřas, Karel (referee) ; Ludvík, Jiří (referee)
4 ABSTRACT Development and testing of novel non-toxic electrode materials, detection arrangements and analytical methods applicable in determination of selected agrochemicals is the main aim of this Ph.D. Thesis. New working electrodes based on silver solid amalgam paste (AgSA-PE) with organic pasting liquid and other based on crystallic silver amalgam (CAgAE) were developed, their electrochemical behaviour investigated and further used in voltammetric determination of widespread and toxic environmental pollutant 4-nitrophenol (4-NP). This analyte could be determined by DPV at AgSA-PE with limit of detection (LD) 1×10í6 mol lí1 and using CAgAE with LD 4×10í7 mol lí1 , both in 0.2 mol lí1 acetate buffer pH 4.8. Attempts to decrease LDs by utilization of adsorptive stripping voltammetry were not successful in either case. Crystallic silver amalgam was also successfully used for construction of microcylindric flow-through cell and tested for amperometric determination of nitrophenol mixture in HPLC-ED system. Both novel electrodes were found to be suitable alternatives to toxic mercury electrodes and the CAgAE seems to be promising working electrode for flowing systems. Method for sample preparation and voltammetric determination of broad-spectrum herbicide Glyphosate in contaminated soil samples was also...
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Voltammetric detection of 27-hydroxycholesterol on boron-doped diamond electrode
Michnová, Kristýna ; Schwarzová, Karolina (advisor) ; Nesměrák, Karel (referee)
The aim of this bachelor thesis was to study the voltammetric behavior of 27-hydroxycholesterol using boron-doped diamond electrode. The influence of several factors on the current response of 27-hydroxycholesterol was investigated: the effect of the supporting electrolyte, concentration of perchloric acid, polarization rate, water content, and pH effect. The study was conducted using cyclic voltammetry in a perchloric acid or sodium perchlorate in acetonitrile. 27-hydroxycholesterol provided a current response in the anodic region with a potential around +1450 mV vs. Ag/0.01 mol l-1 AgNO3 in 1 mol l-1 NaClO4 in acetonitrile in the presence of 0.1 mol l−1 perchloric acid in acetonitrile (water content 0.43 %) and 0.1 mol l−1 sodium perchlorate in acetonitrile. Furthermore, concentration dependence was measured using differential pulse voltammetry resulting in a limit of detection (LOD) of 2.71 μmol l−1 and a limit of quantitation (LOQ) of 9.04 μmol l−1 . It was demonstrated that the direct current voltammetry method does not achieve comparable limit values. Key words 27-hydroxycholesterol, boron-doped diamond electrode, oxidation, oxysterols, voltammetry
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Voltammetry and liquid chromatography of cholesterol, its precursors, and oxidation products
Kubešová, Jana ; Schwarzová, Karolina (advisor) ; Baluchová, Simona (referee)
Electrochemical detection of sterols is difficult. This thesis aims to study the voltammetric behaviour of selected oxysterols, i.e. 25-hydroxycholesterol and 7-ketocholesterol on the boron-doped diamond electrode. Further, an HPLC method with spectrophotometric and electrochemical detection was developed for separation of selected sterols. The study was performed using cyclic and differential pulse voltammetry. 0.1 mol l−1 perchloric acid in acetonitrile (water content 0.55 %) was chosen as the most suitable electrolyte. 25- hydroxycholesterol provides anodic signal at the potential of +1500 mV and 7-ketocholesterol at +1900 mV in that media. Electrochemical reduction of 7-ketocholesterol was also studied. However, the observed cathodic signal isn't reproducible. The stability of oxysterols in the presence of perchloric acid was confirmed by UV-VIS spectroscopy. Calibration dependence of oxysterols was measured using differential pulse voltammetry and resulted in the limit of detection of 0.82 µmol l−1 for 25-hydroxycholesterol and 0.66 µmol l−1 for 7-ketocholesterol. In the second part of the thesis, an HPLC method was developed for the separation of a sterol mixture on a reversed-phase C18 column using a mobile phase containing 50 mmol l−1 sodium perchlorate in acetonitrile with 0% or 6% water...
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Study of DNA-doxorubicine interaction by electrochemical methods on nanostructured electrodes
Přibyl, Jakub ; Fohlerová, Zdenka (referee) ; Kynclová, Hana (advisor)
Cancer diseases are one of the leading causes of mortality worldwide, for this reason, great attention anticancer drugs. Doxorubicin falls into the category of the most widely used cancer drugs. The method of electrochemical impedance spectroscopy were investigated properties of golds electrodes without deposit nanoparticles and electrodes with deposit gold nanoparticles. Using voltammetric measurements we detected doxorubicin and investigated the interaction of doxorubicin with oligonucleotides on gold electrodes without nanoparticles and electrodes modified with gold nanoparticles.
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Thick-film sensors for heavy metals detection
Gajdoš, Libor ; Majzlíková, Petra (referee) ; Prášek, Jan (advisor)
This project describes the possibilities of heavy metals detections in solutions using differential pulse voltammetry with tree-electrode electrochemical thick-film sensors. In the theoretical part, the thick-film technology is described as well as thick-film pastes’ types and compositions, followed by introduction to electrochemistry and electro-analytical methods of measurement. This project also describes the three measured heavy metals – cadmium, lead and copper. In the practical part, heavy metals’ ions detection in solutions using carbon working electrode and determination of the detection limit and sensitivity are described and discussed. Finally the evaluation of obtained results and results comparison to hygienic limits are included.
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Preparation and characterisation of ceramic electroactive materials for Na-ion batteries
Vaněk, Martin ; Libich, Jiří (referee) ; Čech, Ondřej (advisor)
Hlavním cílem této práce je charakterizace vzorků titanátů, jako materiálů pro sodíko-iontové (Na-ion) akumulátory. Syntéza některých vzorků je součástí této práce. Charakterizace je zaměřena na elektrochemické vlastnosti, složení a morfologii použitých materiálů. První část se zabývá lithium-iontovými (Li-ion) akumulátory. Byly vybrány, protože jsou ve vědeckých článcích dobře popsány a základní funkční princip je aplikovatelný také na Na-ion akumulátory. Materiály používáné pro katody, anody a elektrolyty následují po krátké části shrnující parametry a konstrukci Li-ion akumulátorů. Následující kapitola je zaměřena na sodíko-iontové akumulátory. Srovnání sodíku a lithia je následováno materiály používanými pro elektrody a elektrolyty (s důrazem na anodové materiály). Třetí část popisuje analytické metody použité pro charakterizaci elektrod a materiálů. Jedná se o elektrochemickou charakterizaci (cyklická voltametrie a galvanostatické cyklování s potenciálovým omezením), morfologii (rastrovací elektronová mikroskopie) a složení (X-ray difrakční spektroskopie). Poslední dvě kapitoly obsahují syntézu a charakterizaci sodného titanátu a charakterizaci dvou vzorků TiO2. Výsledky této práce jsou shrnuty v závěru.
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Hair as a bioindicator of contamination of risk metals
Zmijová, Marie ; Řezáčová, Veronika (referee) ; Zlámalová Gargošová, Helena (advisor)
The use of hair as a bioindicator of environmental contamination by risk elements is becoming more and more common. This bachelor thesis deals with the use of this matrix for analysis using the voltammetric method. It focuses on the optimization of the method for determining the concentration of cadmium, copper, lead and zinc in real hair samples and monitors the effects on the incorporation of these elements into the hair fiber. The presence of zinc and copper was confirmed in all samples analyzed. Cadmium could only be quantified in one sample. The effect of gender and age on the concentration of elements has not been demonstrated. Concentration of lead has been linked to smoking, with higher concentrations found in smoker’s hair than in non-smoker’s.
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Polarographic analysis of water
Klečka, Tomáš ; Rozman, Jiří (referee) ; Čížek, Martin (advisor)
This bachelor's project creates the necessary theoretical foundation of polarography and voltametry in the first part, which is needed to successful measurement using these technics. In the second part there is realized measurement with anodic stripping voltametry and accomplished evaluation in MATLAB. Finally there is example of procedure for laboratory task with polarograph.
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