Dissertations / Theses on the topic 'Spektrofotometria UV'

Zaawansowana aparatura badawcza umożliwiła badanie materiałów różnorodnego pochodzenia. Dlatego znalazła ona zastosowanie w wielu dziedzinach nauki, gdzie stanowi podstawowe narzędzie w ocenie fizykochemicznych właściwości próbek. Jednak kompleksowa charakterystyka próbki pociąga za sobą pozyskiwanie danych o złożonej strukturze. Opisując każdą analizowaną próbkę za pomocą od kilku do kilku tysięcy zmiennych otrzymuje się tzw. dane wielowymiarowe, co pociąga za sobą potrzebę zastosowania metod matematycznych, pozwalających na analizę i interpretację wyników oraz formułowanie wniosków. W tym celu korzysta się z metod chemometrycznych, w skład których wchodzą metody wstępnego przygotowania danych do analizy, metody eksploracyjne oraz metody modelowania danych. Szczególnie interesujące są metody eksploracyjne ozwalające na wgląd w ukrytą strukturę analizowanych danych oraz ujawnienie zależności pomiędzy próbkami i/lub parametrami. Jednym z wariantów metod eksploracyjnych są metody grupowania danych, które są szczególnie przydatne w kontekście wyodrębniania grup podobnych obiektów. Podobieństwo analizowanych próbek, oceniane jest na podstawie ich odległości w przestrzeni eksperymentalnej (te które znajdują się blisko siebie wykazują podobne właściwości fizykochemiczne). W celu określenia podobieństwa pomiędzy próbkami wykorzystuje się tzw. miary podobieństwa, które są matematyczną interpretacją odległości pomiędzy nimi. Wzrastająca kompleksowość danych pociąga za sobą potrzebę modyfikacji i rozwoju nowych metod eksploracyjnych oraz miar odległości. W związku z czym w niniejszej pracy doktorskiej skupiono się na modyfikacji algorytmu DBSCAN w celu eliminacji problemu błędnego przypisania obiektów brzegowych do odpowiednich grup w przypadku grup sąsiadujących ze sobą w przestrzeni eksperymentalnej. Modyfikacja algorytmu polegała na zmianie sposobu przetwarzania obiektów oraz przypisaniu obiektów brzegowych do grup na podstawie odległości euklidesowej pomiędzy obiektami brzegowymi, a środkami wyodrębnionych grup obiektów. Następnie skupiono się na rozwinięciu koncepcji nowej miary odległości (sij) pozwalającej porównywać ze sobą dwuwymiarowe chromatograficzne odciski palca, w których występuje problem koelucji substancji i przesunięć pików w czasie. W ostatniej części pracy rozważano problem niepewności pomiarowej towarzyszącej danym eksperymentalnym. Dotychczas, błąd pomiarowy był pomijanym elementem w trakcie analizy danych. Aktualnie rozwój algorytmów uwzględniających niepewności pomiarowe uzyskiwanych danych stanowi nowy trend w pracach naukowych. Korzystając z osiągnieć zaprezentowanych w [1], zaproponowano uwzględnienie niepewności pomiarowych modelowanych dla każdego obiektu np. w algorytmie DBSCAN, poprawiając efektywność metody.

Od wielu lat w Zakładzie Chemii Analitycznej, Instytutu Chemii Uniwersytetu Śląskiego, pod kierunkiem pana profesora Franciszka Buhla są prowadzone systematyczne badania nad zastosowaniem sprzężonych reakcji redoks i kompleksowania do oznaczania substancji o znaczeniu biologicznym, farmaceutycznym i biomedycznym. Praca niniejsza podejmuje problem badawczy związany z analizą związków fenolowych i alkaloidów purynowych o właściwościach redukujących. W tym zakresie wykonane zostały następujące badania: 1. Opracowano spektrofotometryczne metody oznaczania kwasu salicylowego, kwasu galusowego, kwasu taninowego, (+)-katechiny, kofeiny i teofiliny. Jako podstawę efektu analitycznego wykorzystano reakcje redoks i kompleksowania przebiegające w dwoch układach odczynnikow: Ce(IV) - arsenazo III i Fe(III) - 2,2’-bipirydyl. W wyniku reakcji jonow metalu na wyższym stopniu utlenienia z organicznym analitem o właściwościach redukujących powstaje bezbarwna, utleniona postać analitu oraz stechiometryczna ilość jonów metalu na niższym stopniu utlenienia , które są wiązane w związek kompleksowy przez odczynnik chromogenny. W pierwszym układzie odczynników reagują wszystkie badane reduktory. Natomiast wykorzystując do redukcji kationów Fe3+ kwas salicylowy, kofeinę i teofilinę, stwierdzono że reakcja zachodzi powoli i w niewielkim stopniu, co uniemożliwiło zastosowanie pary odczynników Fe3+ i 2,2’-bipirydyl do opracowania nowych warunków spektrofotometrycznego oznaczania tych reduktorów. Wykreślone krzywe spektrofotometryczne dla prób: kation metalu - reduktor - odczynnik kompleksujący, pozwoliły wnioskować o obecności w badanych roztworach związków kompleksowych, odpowiednio: [Ce(A)]~ oraz [Fe(2,2’-bip)3 ]2+. Stąd też analitycznymi długościami fali światła były wartości charakterystyczne dla tych związków kompleksowych, tzn. A.max = 655 nm oraz A™ax = 522 nm . W badaniach nad optymalizacją warunków oznaczania ustalono nadmiary reagentów potrzebnych do przeprowadzenia oznaczeń oraz warunki w jakich zachodzą reakcje redoks i kompleksowania. W temacie walidacji opracowanych metod wyznaczono zakresy liniowości oraz zbadano precyzję oznaczeń. 2. Przeprowadzono badania chromatograficzne nad optymalizacją warunków rozdzielania kwasów: salicylowego, galusowego, taninowego; (+)-katechiny, kofeiny i teofiliny, na cienkiej warstwie żelu krzemionkowego F2 5 4 . Stwierdzono, że najlepsze rezultaty rozdzielenia wymienionych substancji uzyskuje się stosując fazę rozwijającą o składzie: chloroform - octan etylu - kwas mrówkowy w stosunku objętościowym 5:4:1. Jako wywoływacz stosowano światło UV (A, = 254 nm) oraz układ odczynników: Fe(IIl) - 2,2’-bipirydyl. W optymalnych warunkach rozdzielania wyznaczono wartości Rf dla badanych substancji oraz indeksy wykrywalności. Ustalono warunki izolacji kwasu taninowego z materiałów złożonych wykorzystując technikę chromatografowania dwukierunkowego prostopadłego. Wyznaczono krzywe wzorcowe spektrofotometrycznego oznaczania kwasu galusowego i taninowego, po ich izolacji na cienkiej warstwie żelu krzemionkowego, wykorzystując jako podstawę efektu analitycznego sprzężone reakcje redoks i kompleksowania przebiegające w układzie: Fe (III) - 2,2’-bipirydyl. Prowadząc analizę chgromatograficzną w ustalonych warunkach wyznaczono krzywą wzorcową planimetrycznego oznaczania (+)-katechiny. Wizualizację obrazu chromatograficznego uzyskano poprzez spryskanie płytek roztworami Fe(III) a następnie 2 ,2 ’-bipirydylu. Dokonano analizy spektrodensytometrycznej kwasu galusowego, kofeiny i (+)-katechiny na cienkiej warstwie. 3. Wykorzystując sprzężone reakcje redoks i kompleksowania przebiegające w układzie odczynników Ce(IV) i arsenazo III, opracowano metodę oznaczania kwasu taninowego po jego izolacji z materiałów złożonych na drodze chromatografii bibułowej. Badania nad optymalizacją warunków rozdzielania kwasów: salicylowego, galusowego i taninowego przeprowadzono stosując jako fazę stacjonarną bibułę Whatman nr 3. Najlepsze rezultaty rozdzielenia uzyskano przy zastosowaniu fazy rozwijającej o składzie: izopropanol - izobutanol - woda, w stosunku objętościowym 3:2:4. Chromatogramy wywoływano poprzez spryskanie roztworami Fe(III) i 2,2’-bipirydylu. W ustalonych warunkach wyznaczono krzywą wzorcową oraz dokonano oceny statystycznej wyników. 4. Zbadano możliwość spektrofotometrycznego oznaczania kofeiny z wykorzystaniem pary odczynnikow Ce(IV) i arsenazo III, po izolacji analitu techniką SPE. Stosując kolumienki z fazą oktadecylową i wymywając osadzoną kofeinę chloroformem, wyznaczono krzywą wzorcową oznaczania kofeiny po jej ekstrakcji do fazy stałej. 5. W celu zbadania przydatności opracowanych procedur analitycznych oznaczono wybrane reduktory w preparatach farmaceutycznych i naturalnych: oznaczono teofilinę w preparacie Theophyllinum metodą spektrofotometryczną wykorzystującą parę odczynnikow Ce(IV) i arsenazo III dokonano oceny zawartości garbnikow hydrolizujących w liściach jeżyny metodą spektrofotometryczną wykorzystującą parę odczynnikow Ce(IV) i arsenazo III, po izolacji kwasu taninowego na drodze chromatografii bibułowej oznaczono kwas galusowy po izolacji z preparatu „Acifungin forte” techniką TLC. W badaniach wykorzystano opracowaną metodę spektrofotometryczną opartą na reakcjach redoks i kompleksowania przebiegających w układzie Fe(III) i 2,2’-bipirydyl oraz metodę densytometryczną dokonano ilościowej oceny zawartości (+)-katechiny w preparacie „Green tea” oraz w naparze z liści zielonej herbaty, wykorzystując opracowaną metodę densytometrycznego oznaczania analitu t zastosowano opracowane metody: spektrofotometryczną i densytometryczną do oznaczania kwasu galusowego w naparach z różnych rodzajów herbat, po ich rozdzieleniu chromatograficznym techniką TLC opracowaną metodę densytometrycznego oznaczania kofeiny zastosowano do oceny zawartości analitu w naparach z rożnych rodzajow herbaty, liści Yerba Mate oraz preparatów zawierających Guaranę. opracowane warunki spektrofotometrycznego oznaczania kofeiny po jej izolacji techniką ekstrakcji do fazy stałej zastosowano do jej oznaczania w preparacie „Green tea” oraz preparatach zawierających Guaranę

The behaviour of humic acids in aqueous solutions is closely connected to the content of acid functional groups and their dissociation abilities. The titration methods are the most often used for the research of acid-base characteristics of humic acids, their results should lead to the determination of the content of functional groups and their pKa. However the determined values depend on many factors including the titration speed. The spectrophotometric determination of dissociation constant was used in this diploma thesis. Reliability of this method was confirmed in bachelor thesis where is mentioned that spectrophotometric determination of pKa corresponds with realistic dissociation behaviour of humic acids in the water much more better than values obtained from titration methods. The principle of newly used spectrophotometry method is the preparation of humic acids solutions in three different media with different pH values. Acid groups of humic acids are practically completely dissociated in intensely basic environment and the measured absorbance is caused by anion of „humate“. On the contrary their dissociation in acid environment is suppressed so much that we measure the absorbance of non-dissociated molecules of humic acids. Deionized water was used like neutral solvent. Water was replaced by acetic buffer in this thesis because of water’s properties which have significant influence on solutions' pH. Buffer was used for diluting or for solubilisation and in these both cases more stable pH values were occurred. The aim of this diploma thesis is investigate UV/VIS spectra of various solutions of humic acids with different values of pH and determinate mean value of pKa of humic acids which could be used like comparison of dissociation behaviours for vary samples. Values of acid dissociation constant were determined from measured dates and compared with values obtained by titration method. The UV/VIS spectra gained in combination with the results of pH measuring and the conductivity next showed the differences in the behaviour of differently prepared samples of humic acids.

Presented diploma thesis deals with the analysis of juices of selected red and white currant varieties. The theoretical part is dedicated to the characteristics of a currant, biologically active substances of its fruits, its growing proces and the utilization of currants in the food industry. The analyzed parameters of currants - phenolics, anthocyanins and vitamin C are also characterized in the theoretical part with possibůe methods of their determination. The experimental part is devoted to the preparation of samples and the working practices of individual analysis. Six selected varieties of white and eleven varieties of red currant from Research and Breeding Institute of Pomology Holovousy Ltd. and six varieties of white and ten varieties of red currant from private grower were used for the analysis. Total phenolics and anthocyanins were determined spectrophotometrically, the content of vitamin C was determined by HPLC. Higher values of these compounds were measured mainly in the varieties of Research and Breeding Institute of Pomology Holovousy Ltd. Varieties of red currants contained higher amounts of total phenolics and anthocyanins while white currants contained higher amounts of vitamin C.

This master´s thesis deals with the study of the incorporation of low and high molecular weight substances into liposomal systems. The aim of the work was to determine the encapsulation efficiency (EE) of the active substance and the influence of individual components of the liposomal system on EE. Liposomes were prepared from dipalmitoylphosphatidylcholine. They were stabilized by cholesteroland and phosphatidic acid was added to give a negative charge. Stealth properties gain the binding of polyethylene glycol and other trimethyl chitosan we enabled the entry of liposomes into the bloodstream by the paracellular pathway. Vitamin C and the enzyme bromelain were used for incorporation into liposomes. UV-VIS spectrophotometry was used to determine the encapsulation efficiency of liposomes prepared by combining the individual components. It has been suggested that vitamin C and the enzyme can be incorporated into liposomes, but an enzyme with a higher EE. Furthermore, phosphatidic acid and trimethyl chitosan have been found to affect EE, which increases the EE of vitamin C and decreases the EE of the enzyme.

This diploma thesis deals with humic acid gels and their ability to bind metallic ions on their surface. In the thesis, there was studied the adsorption of copper ions on the provided gels. The gels were prepared by dissolving the humic acid in sodium hydroxide or sodium tripolyphosphate and then precipitated with hydrochloric acid or metal chlorides. Adsorption was studied at different concentrations of the copper (II) chloride and measured on UV-VIS spectrophotometer. It was proved from measuring that gels made from sodium tripolyphosphate are adsorbing less copper ions than the ones prepared by sodium hydroxide. Also, the copper ions are bound with smaller force on gels prepared with polyphosphate. Gels precipitated with magnesium chloride adsorb much more than gels precipitated with acid, thus in the case of gels sequestered metal ions extracted higher.

This thesis deals with the preparation of the combined alcoholic beverages based on wine and fruit juices. The fruit juices were obtained from the selected fruits as honeysuckle, mulberry, dogwood, rose hips, elderberry, buckthorn and aronia. Some chemical properties e. g. total fenolics, total anthocyanins, vitamin C and sacharides were determined for characterization of the mentioned juices. As well as chemical parameter of juices, the same chemical parameters were determined on wine. There were prepared three sets of combined beverages from wine and juices. The two best evaluated beverages were chosen on the basis of their sensory evaluation. In the end, the same chemical properties were determined in both particular juices and resulting beverages.

This Ph.D. thesis is focused on kinetic study of propene and hex-1-ene coordination polymerizations initiated by complex [(2-tBuC6H4)N=C(1,8-naphtalenediyl)C=N(2-tBuC6H4)]NiBr2 activated by simple organoaluminium compounds and on product properties. In first three parts proper activators are chosen in model polymerizations. The attention is paid to the reproducibility of polymerizations and analytical methods. The fourth part is focused on propene polymerization kinetics with the aim to define optimal reaction conditions, especially polymerization temperature and time. The four part concerns also properties of polymers. The fifth and sixth parts deal with hex-1-ene polymerization kinetics conducted at various activator/initiator molar ratios and various catalytic precursor concentrations, to find out kinetic orders with respect to catalyst and cocatalyst concentration. Last part is oriented on detail mechanistic investigation of nickel diimine complexes activation process. Results of measurements in presence or absence of monomer enabled to propose new interpretation of UV-vis spectra based on concrete structures of absorbing species.

This diploma thesis focuses on quinine solutions and quality of these solutions after applying plasma discharge. These electric discharges can be used to destroy some substances from the water. The theoretical part is focused on description of electric discharges in liquids and on the properties of quinine. In the experimental part, the properties of quinine solutions containing different electrolytes were analysed by UV-VIS spectrophotometer and fluorescence spectroscopy. Two different types of configurations of plasma discharges in liquids were used. Solutions were compared on the base of different concentration of quinine, different electrolytes, different configurations of plasma discharges and pH values of the solutions. Furthermore, the experimental work focuses on quinine solutions with the sodium nitrate. The time instability of the solutions was analysed. Also, the influence of the solution age and different types of the plasma discharge on the excitation and emission spectra of quinine were investigated.

Creatine is nitrogen-containing organic acid which naturally occurs in the human body. The aim of this work was to determine the optimal dose of creatine in combination with vitamin C and magnesium for male respondents aged 18-26 years. They were divided into two groups differing in the creatine dosage. Group 1 took smaller dose of creatine (3 g per day) and group 2 higher dose of creatine (10 g per day). Both groups took both magnesium and vitamin C at constant doses throughout the study. The effects of significantly different dose of creatine in the individual groups were compared with each other in terms of the performance of individuals in the powerlifting, the anthropological changes and the overal metabolism of the intakes. In all disciplines of powerlifting, group 1 recorded higher average weight gains, which were not found to be statistically significant at a significance level of alpha 0,05. Anthropological changes were measured using the InBody 160 and a diagnostic measuring tape. In both cases, group 1 recorded better results than group 2, but these results were not statistically significant at a significance level of alpha 0,05. The total metabolism of the accepted dietary supplements was investigated through analytical methods. The urine of each respondent was regularly collected and subsequently analyzed during the research. Determination of creatinine, a creatine waste product, was performed by UV-VIS spectrophotometry using the Jaffe reaction. Vitamin C was analyzed by RP-HPLC. Magnesium was determined by the ICP-OES method. After creatine suplemantion of 3 per day, group 1 showed a slight increase in creatinine in the urine, but still in the physiological range. At the significance level alpha 0,05 there was no statistically significant difference. Group 2 showed an increase above the physiological limit which was already a statistically significant difference. Overall, creatine supplementation of 3 g per day has been found as a sufficient intake of creatine needed to build up muscle mass, increase energy metabolism and overall physical performance. The metabolization itself works very well and within the physiological values.

This thesis is focused to the analysis of selected varieties of honeysuckle kamtschatica (Lonicera caerula var kamtschatica) and their comparison in terms of the content of biologically active substances. There were analysed only varieties grown in 2014. Theoretical part elaborates and characterized various parameters of biologically active compounds such as phenolic, anthocyanins and ascorbic acid and possibilities of their determination. Further it briefly surveys Kamchatka honeysuckle, its taxonomic and morphological properties and its nutritional properties. The experimental part of the work was focused on the description of the methods used for the analysis of biologically active substances and their analysis. Polyphenolic compounds and anthocyanin’s were determined spectrophotometrically and vitamin C was determined by high-performance liquid chromatography. The results and varieties were compared with each other. Overall, we can say that the variety with the highest content of all three analysed biologically active substances is a variety Valchová, which had the second highest content of polyphenolic compounds (546.3 mg · 100 g-1 fruits), the third highest contend of ascorbic acid (35.1 mg · 100 g-1 fruits) and the sixth highest content of anthocyanin (170.8 mg · 100 g-1 fruits)

In this diploma thesis, the interactions between polyelectrolyte and surfactant at low and also at high concentration were studied. There was used pyrene as fluorescent probe during the fluorescence spectroscopy measurement, a cationic surfactant cetyltrimethylammonium bromide and as a main polyelectolyte has been chosen sodium polystyrene sulfonate at 1 MDa molecular size. In the medium containing 0.15 M NaCl we could observed a creation of the complexes – precipitates in the surrounding of CMC concentration and behind of this concentration. In the mixtures containing sodium polystyrene sulfonate and hyaluronan together, there was stronger tend to keep aggregation properties of sodium polystyrene sulfonate during difference concentration ratios. Beyond CMC concentration, hyaluronan starts to influence the aggregation properties of the system as well.

This diploma thesis is focused on microdetermination of cobalt by UV-VIS spectrophotometry with organic agents and comparison with atomic absorption spectrometry. In the first part properties, occurance and importance of cobalt in the environment are desribed, complete with as a part of vitamine B12. Attention is also given to cobalt compounds, especially in the oxidative states +II and +III. Methods of preconcentration and preparation cobalt determination in real samples are adduced. In this thesis are described some optical analytical methods with accept on spectrophotometric agents for determination of cobalt. The experimental part of this thesis icludes optimalization of the spectrophotometric determination of cobalt with choosen organic agents 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol and optimalization of atomic absorption spectrometry for cobalt determination. All of real samples of water (surface, underground, mineral and waste) were measured by both 4-(2-pyridylazo)resorcin and 2-(5-Brom-2-pyridylazo)-5-diethylaminophenol via UV-VIS and via atomic absorption spectrometry. Results of determinations were compared. A sample of vitamine B12 was measured too by all techniques.

This master's thesis discusses the use of UV/VIS spectrophotometry in chemistry teacher education. Optical methods principles are described in theoretical part of the thesis, and. the main part is dedicated to UV-VIS spectrophotometry. Tasks for quantifying and qualifying substances determination are described in experimental part. Educational tasks are described in a way so that chemistry teachers could use for instructions.

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology and Toxicology Candidate: Tereza Morávková Supervisor: Assoc. Prof. Přemysl Mladěnka, Pharm.D., Ph.D. Title of Thesis: Assessment of the complex stoichiometry of the active dexrazoxane metabolite ADR-925 with iron and copper by the standard Job'smethod Iron and copper are important trace elements which participate on many physiological processes in humans. Their kinetics in the organism is tightly regulated since both lack or excess of these elements are associated with pathological states. Free ions of iron and copper can catalyse reactive oxygen species (ROS) production and hence cause damage to proteins and DNA. Imbalance in these metals is linked with diabetes, cardiotoxicity, cirrhosis of the liver and neurodegenerative diseases as Alzheimer's disease or Parkinson's disease. Dexrazoxane is a drug with documented protecting effect against cardiotoxicity of anthracyclines. A former theory associated its protective effects against these cytotoxic drugs with the iron-chelating properties of its active metabolite ADR-925. The goal of this diploma thesis was to explore if ADR-925 is able to chelate Fe2+ , Fe3+ , Cu+ a Cu2+ ions at physiologically and pathophysiologically relevant pH values (4,5; 5,5; 6,8 and 7,5) and...

The aim of the thesis on "Evaluation of the color of honey" was to determine why the instrument can not Lovibond Honey Colorpod 440110 to evaluate color of all types of honey and compare results of with spectrophotometric measurement methods. The work is divided into theoretical and practical part. The theoretical part is dedicated to honey, its composition and methods of evaluating color. The practical part describes the results obtained instrument Lovibond Honey Colorpod -- 440110, spectrophotometers Konica Minolta -- 3500d a FT -- NIR Antaris. In UV/VIS region not been demonstrated reason of errors of photometer. Maximum lightness had a very light honeys and the largest share of yellow had light honey. The highest values of absorbance attain dark honeys. In color space CIE L* a* b* had the largest share of red. Evaluation of the color of honey in the UV/VIS can not prove adulteration of honey always unambiguously, but there are signs by which honey can be described as suspicious. By analyzing the NIR spectrum is falsification of honey demonstrated using discriminant analysis.

This thesis is focused on the application of two working electrodes of graphite suitable for determination of oxidizable tumour biomarkers. It deals with the study of electrochemical behavior of urinary indican. For the determination the technique of differential pulse voltammetry (DPV) was used on carbon paste electrode and film composite paste electrode in Britton-Robinson (BR) buffer. In the first step optimal conditions were determined to find the lowest limit of determination (LQ) of this substance. BR buffer of pH 3 was chosen as the optimum medium for determination on a carbon paste electrode and BR buffer of pH 2 was used as the optimum medium for the determinaton using a film composite electrode. Performance for both electrodes was observed in a concentration range of from 1 · 10-6 to 5 · 10-5 mol·l-1 . The limit of determination for measurements on a carbon paste electrode was 0.7 µmol·l-1 and the film composite electrode was 1.7 µmol·l-1 . Possibility of the acummulation of indican was examined in order to increase sensitivity and decrease of limit of quantification. However, after 5 minute sorption, no increase in response was observed and the accumulation step was not inserted. Developed method was tested on the determination of urinary indican in human urine matrix after solid phase...

The diploma thesis deals with the light permanency changes of some chosen tropical woods. Their trade names are garapa (Apuleia Leiocarpau), angelim (Hymenolobium Petraeum), meranti (Shorea spp), sapeli (Entandrophragma cylindricum), merbau (Intsia bijuga), massaranduba (Manikara), teak (Tectona grandis), iroko (Chlorophora excelsa) and eucalyptus (Eucalyptus grandis). The woods are surface modified by means of four different surface modifications both with and without a usage of an alcohol base. All samples were lighted up by artificial sunlight from the xenon lamp for 106 hours by lighting 209,7 KJ/m2. The colour changes were measured during the exposition according to the greyscale and spectrophotometer in the CIEL *a*b* color model. Then the individual woods' color changes depending on the surface modification were assessed by the color difference deltaE*.

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....