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Voltammetric Determination of 4-Nitrobiphenyl at a Mercury Meniscus Modified Silver Solid Amalgam Electrode
Horáková, Eva ; Schwarzová, Karolina (referee) ; Barek, Jiří (advisor)
The presented bachelor thesis is devoted to study of electrochemical behavior of 4-nitrobiphenyl (4-NBP) and to finding of 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). The aim was to achieve the lowest possible limit of determination and to verify the applicability of the newly developed method for determination of 4-NBP in model samples of drinking water. Methanol-acetate buffer pH 4,8 (3:7) was found as an optimum medium for the determination of 4 NBP at a m-AgSAE in deionized water. During DCV it is not necessary to apply electrochemical regeneration of the working electrode, during DPV it is proper to apply following regeneration potentials: Ereg,1 = 0 mV, Ereg,2 = -1300 mV. The concentration dependence of the peak current was found to be linear for both methods for 10-5, 10-6 and 10-7 mol∙l-1 concentration ranges. The limit of determination of 4-NBP both by DCV and by DPV is 2∙10-7 mol∙l-1. The optimum medium for the determination of 4-NBP in drinking water is the mixture of the sample and acetate buffer pH 4,8 in the 9:1 ratio.. During DCV regeneration was not applied, during DPV it was applied with the following regeneration potentials: Ereg,1...
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The utitilization of boron-doped diamond thin film electrode for the voltammetric and amperometric determination of amino derivatives of biphenyl
Maixnerová, Lucie ; Zima, Jiří (referee) ; Schwarzová, Karolina (advisor)
The aim to this work was to develop methods for the determination of 2 aminobiphenyl (2-AB), 3 aminobiphenyl (3-AB), and 4-aminobiphenyl (4-AB) in model mixtures. Concretely, the direct determination of the mixture of studied analytes has been tested using spectrophotometry and differential pulse voltammetry (DPV). Furthermore, separation and detection of 2-AB, 3-AB, and 4-AB have been performed using high performance liquid chromatography with electrochemical detection (HPLC-ED) with boron-doped diamond film thin electrode (BDDFE) in ,,wall-jet" configuration and using high performance liquid chromatography with UV detection (HPLC-UVD). It was found out that the spectrophotometric determination of 2-AB, 3-AB, and 4-AB is impossible in their mixture because of nearby values of local absorption maxima wavelengths of all three analytes studied. Upon the determination of 2-AB, 3-AB, and 4-AB in their mixture using DPV in BR buffer pH 2.0, the difference in peak potentials of 2-AB and 3-AB is too low for their determination in mixture. Upon the determination of mixture containing 2-AB and 4-AB in BR buffer pH 12.0, the limits of determination (LDs) were obtained in the concentration order of 10-6 mol.l-1 for 2-AB and 10-7 mol.l-1 for 4-AB. LDs for the mixture containing 3-AB and 4-AB were obtained in the...
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Cobalt phthalocyanines as sensors for detection of htiol groups
Vaňková, Kateřina ; Nesměrák, Karel (advisor) ; Schwarzová, Karolina (referee)
Title: Cobalt phthalocyanines as sensors for determination of thiol groups Annotation: The possibility of employment of cobalt phthalocyanine as a material for the modification of HOPG electrode for construction of a sensor for quantification of thiol groups was studied. Thiol groups are occurring in various biologically active substances (sulfur amino acids). The electrochemical behavior of cobalt tetraneopentoxy-phthalocyanine (CoTNPc) in the water/organic phase system was studied, and individual peaks of cyclic voltammogram of the compound were identified. The electrodeposition of CoTNPc on HOPG electrode was found as a suitable method for construction of the sensor for quantification of thiol groups. The reproducibility of fabrication of the sensor and its time-stability was studied. The calibration dependencies for model analytes (cysteine hydrochloride and homocysteine) were measured. Key words: thiols, phthalocyanines, amperometric sensor, cyclic voltammetry
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Determination of double bond position in wax esters by dimethyl disulfide derivatization and mass spectrometry
Háková, Martina ; Schwarzová, Karolina (advisor) ; Coufal, Pavel (referee)
Wax esters are substantial constituents of natural waxes, which can be found in many living organisms. Properties of lipids, including wax esters, may be significantly influenced by the position of double bond. In this diploma thesis the location of double bonds was determined by dimethyl disulfide (DMDS) derivatization followed by detection using tandem mass spectrometry with atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI). We managed to measure the APCI and ESI MS/MS spectra of 8 different wax esters with different position of double bond. Diagnostic ions determining double bond position were identified. This method could be used in HPLC/MS analysis of wax esters, which cannot be analyzed by GC/MS. It was shown that the DMDS derivatization reaction and mass detection with APCI ionization is also suitable for locating double bonds in alkenes.
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Voltammetric determination of 1-nitropyrene using silver solid amalgam electrode in miniaturized detection cell
Karásek, Jindřich ; Navrátil, Tomáš (referee) ; Schwarzová, Karolina (advisor)
Jindřich Karásek, diplomová práce KATA 2010 Abstract Meniscus-modified silver solid amalgam electrode was used in miniaturized detection cell. It was constructed for determination of various analytes in decreased volume using 1-nitropyrene as a model analyte. Working electrode was placed together with reference (Ag/AgCl/3 mol.l-1 KCl) and Pt wire auxiliary electrode in miniaturized voltammetric cell, using 120 µl of base electrolyte for measurements. The oxygen was removed from measured solutions by addition of saturated solution of sodium sulphite. Base electrolyte was composed of methanol and Britton - Robinson buffer pH12,0 in the ratio of 7:3. Determination was optimized for DC voltammetry and differential pulse voltammetry. Limits of quantitation were comparable of about 4.10-6 mol.l-1 in both cases. The methods showed reproducible results with relative standard deviation <3.65 % (n = 10).
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