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...

Voltammetric methods for the determination of diazepam (DZ) and nordiazepam (NDZ) were developed. Techniques differential pulse voltammetry (DPV) and DC voltammetry for determination of both substances at meniscus modified silver solid amalgam electrode (m-AgSAE) were used. Effect of pHa in media of mixture of Britton-Robinson buffer and methanol (9:1) and 0,1 mol.l-1 NaOH was studied. Stability of the signal with repeated measurements in 0,1 mol.l-1 and methanol (9:1) was monitored. Optimal pHa 13,2 of 0,1 mol.l-1 NaOH was used for determination of DZ by DPV and DCV techniques. Optimal pHa 10,2 in media of mixture of Britton-Robinson buffer and methanol (9:1) was used for determination of NDZ by DPV and DCV techniques. Under these conditions were measured linear dependences in the calibration. Concentration range of DZ was measured with DCV in range of 1.10-4 - 6.10-6 mol.l-1 and DPV with DCV technique in range of 1.10-4 - 2.10-6 mol.l-1. Concentration range of NDZ was measured with DCV technique in range of 1.10-4 - 4.10-6 mol.l-1 and DPV technique in range of 1.10-4 - 2.10-6 mol.l-1. The limit of detection was calculated for DZ 6,6 .10-6 mol.l-1 with DCV and 1.10-6 mol.l-1 with DPV. The limit of detection was calculated for NDZ 5,5.10-6 mol.l-1 with DCV and 1,7.10-6 mol.l-1 with DPV. Developed method...

Voltammetric methods for the determination of diazepam (DZ) and nordiazepam (NDZ) were developed. Techniques differential pulse voltammetry (DPV) and DC voltammetry were used for determination of DZ and NDZ at meniscus modified silver solid amalgam electrode (m-AgSAE). The effect of pHa on the intensity of signal was observed in the mixture of Britton-Robinson buffer and methanol (9:1), and in the mixture of 0.1 mol.l−1 NaOH and methanol (9:1). The stability of the signal during repeated measurements in the mixture of 0.1 mol.l−1 NaOH and methanol (9:1), and in the mixture of BR buffer and methanol (9:1) was monitored. Optimal pHa 13.2 of medium of 0.1 mol.l−1 NaOH and methanol (9:1) was used for determination of DZ with DPV and DCV techniques. Optimal pHa 10.1 of medium of BR buffer and methanol (9:1) was used for determination of NDZ with DPV and DCV techniques. Under these conditions linear dependencies calibration were measured. Concentration range of DZ was measured with DCV in range of 10x10−5 - 6x10−6 mol.l−1 and with DPV technique in range of 10x10−5 - 2x10−6 mol.l−1 . Concentration range of NDZ was measured with DCV technique in range of 10x10−5 - 4x10−6 mol.l−1 and with DPV technique in range of 10x10−5 - 2x10−6 mol.l−1 . The limit of detection for DZ was calculated 6.6x10−6 mol.l−1 with DCV and...

This Thesis deals with the construction of an electrochemical cell with two types of integrated composite electrodes based on carbon films. Using these electrodes, the voltammetric behavior of environmental pollutant triclosan (5-chlor-2-(2,4- dichlorophenoxy)phenol) was studied. For the construction of composite electrodes, graphite and glassy carbon were used as conductive microparticles. Several types of polymers served as the nonconductive binder. For the measurements, combinations of graphite with polystyrene and graphite with polycarbonate were selected as optimum materials. From the dependence of peak heights on solution composition, a mixture of a buffer of pH 7 and methanol (1:9, V/V) was selected as the optimum medium. In this medium, concentration dependences were measured; calculated triclosan detection limit were 0,49 µmol dm-3 for carbon polystyrene composite electrode and 0,25 µmol dm-3 for carbon polycarbonate composite electrode, respectively. The possibility of further increasing the sensitivity of the determination by the accumulation step was studied. Accumulation of triclosan on carbon polystyrene composite electrode was observed, but the increase in response was connected with the loss of repeatability. Accumulation of triclosan on carbon polycarbonate composite electrode was...

Propyl gallate (PG) is a significant synthetic antioxidant and preservative. Its determination has been studied at carbon paste electrode (CPE) using differential pulse voltammetry (DPV) and high performance liquid chromatography with electrochemical detection (HPLC-ED) and with UV spectrometric detection (HPLC-UV). Concentration dependences were measured in the media of Britton-Robinson buffer (pH 5) and methanol (20 %, v/v) by DPV and the limit of detection 0,6110-7 moldm-3 was obtained. Using HPLC with a mobile phase consisting of 0,01 moldm-3 phosphate buffer (pH 4) and methanol (50 %, v/v) with potential of working electrode E = +0,8 V and detection wavelength λ = 280 nm, concentration dependences were measured. Limit of detection was determined to 0,39 moldm-3 for HPLC-ED and 4,95 moldm-3 for HPLC-UV. After verification of the extraction procedure PG was determined in vegetable oil. The resulting value of 3,2 mgkg-1 corresponds with permited limits.

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...

The thesis deals with liquid aprotic electrolytes based on mixtures of ionic liquid and solvent. EmimBF4, namely 1-ethyl-3-ethylimidazolium tetrafluoroborate, was used as the starting ionic liquid. A mixture of propylene carbonate, ethylene carbonate and dimethyl carbonate was used as solvents. Electrolytes were enriched with two electrolyte salts LiBF4 and NaBF4 from the resulting mixtures selected the most suitable electrolytes for Li-ion and Na-ion accumulators. Electrolytes were selected taking into account the required properties: the width of the potential window, the measured electrical conductivity and, last but not least, the safety.

This work deals with thick-film sensor’s electrodes optimization. The main goal of this work is to find suitable design of the electrodes for the best and reproducible current response of thick-film sensors.

Diploma thesis is involved in basic properties of nickel materials for alkaline accumulators. Practical part deals with measuring of nickel hydroxides by cyclic voltametry. Next practical part is above measuring and optimalization various proportion of nickel and cobalt in layer made by electrodeposition on nickel electrodes.