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Voltammetric Determination of 2,4-Dichlorophenoxyacetic Acid and 2,4-Dichlorophenol on a Screen-Printed Carbon Electrode
Jančová, Jana ; Vyskočil, Vlastimil (advisor) ; Fischer, Jan (referee)
The aim of the presented Master Thesis was to study an electrochemical behaviour of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) resulting in the founding of optimum conditions for their voltammetric determination at a screen-printed carbon electrode (SPCE) using DC voltammetry (DCV) and differential pulse voltammetry (DPV). Voltammetric behaviour of both compounds was investigated in dependence on the pH of the medium (realized using Britton-Robinson buffer). The optimum pH for the voltammetric determination of 2,4-D on the SPCE was chosen to be pH 5,0 for both voltammetric techniques, and, for 2,4-DCP, it was chosen to be pH 6,0 for both voltammetric techniques. The determination of 2,4-D at a concentration of 1·10-4 μmol·L-1 showed good repeatability for both voltammetric techniques used (1.3% for DCV and 0.7% for DPV), and, for 2,4-DCP, it showed acceptable repeatability for both voltammetric techniques used (1.3% for DCV and 4.8% DPV). Under optimum conditions, the calibration dependence of 2,4-D was measured for DCV in the concentration range of 10-100 μmol·L-1 , with limit of quantification (LOQ) of 1.0 μmol·L-1 and limit of detection (LOD) 0.3 μmol·L-1 . Under optimum conditions, the calibration dependence of 2,4-D was measured for DPV in the concentration range...
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Voltammetric and amperometric determination of homovanillic, vanillylmandelic, and 5-hydroxyindole-3-acetic acid
Němečková, Anna ; Barek, Jiří (advisor) ; Labuda, Ján (referee) ; Skopalová, Jana (referee)
Presented dissertation thesis is focused on the development of electrochemical methods for the determination of three important tumour biomarkers, namely homovanillic acid (HVA), vanillylmandelic acid (VMA), and 5-hydroxyindole-3-acetic acid (5-HIAA). First part of the study is focused on electrochemical behaviour of these analytes in batch arrangement using differential pulse voltammetry (DPV) at screen-printed carbon electrodes (SPCEs). It has been proved that presented method is sufficiently sensitive for monitoring above mentioned analytes. Moreover, it can be used for determination of HVA and VMA in mixture. Obtained limits of detection (LODs) were 0.24 µmol·L-1 for HVA, 0.06 µmol·L-1 for VMA, and 0.12 µmol·L-1 for 5-HIAA. The requirements to speed up the analysis and at the same time to reduce its price initialized our study of the determination of tested biomarkers in flow systems. Firstly, flow injection analysis with amperometric detection was investigated for the determination of all three biomarkers at the same SPCE, and then an analogous determination of structural more similar pair, HVA and VMA, was performed at a boron doped diamond electrode (BDDE). Obtained LODs of optimized methods were as follows: at SPCE 0.07 µmol·L-1 for HVA, 0.05 µmol·L-1 for VMA, and 0.03 µmol·L-1 for 5-HIAA,...
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Voltammetry with Preliminary Extraction as a New Approach for Rapid Determination of Formaldehyde in Wood-Based Products
Dvořák, Pavel ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
The aim of the presented Diploma Thesis was to develop a new method for the indirect determination of formaldehyde in wood-based products using gas-diffusion microextraction coupled with electrochemical detection on unmodified screen-printed electrodes (MLEM-SPCE). Formaldehyde released from the sample is derivatized using an acetylacetone reagent present in an acceptor solution. The product of derivatization of formaldehyde with acetylacetone is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which forms a selective oxidation voltammetric peak at a potential of 0.4 V. Detection and quantification limits of 0.57 mg kg−1 and 1.89 mg kg−1 , respectively, were obtained, together with intra- and inter-day precision below 10% (as relative standard deviation, RSD). The developed methodology was applied to determine formaldehyde content in seven samples. Similar results were obtained from the European standard method EN 717-3 with a significant reduction of total analysis time. The developed method MLEM-SPCE, which combines the use of a new sample preparation procedure for volatile compounds with the firstly introduced determination of formaldehyde (as the derivative product DDL) on unmodified SPCEs, proves to be a promising alternative for the determination of formaldehyde in wood-based products and other samples.
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Voltammetric Determination of Genotoxic 2-Nitrofluorene at Screen-Printed Carbon Electrodes
Jelínková, Lenka ; Vyskočil, Vlastimil (advisor) ; Zima, Jiří (referee)
of the Bachelor Thesis Voltammetric behavior of genotoxic 2-nitrofluorene (NF) has been investigated using direct current voltammetry (DCV) and differential pulse voltammetry (DPV) at a screen- printed carbon electrode (SPCE). The optimum conditions have been found for its determination in a concentration range from 1×10−6 to 1×10−5 mol l−1 for DCV technique and from 1×10−7 to 1×10−5 mol l−1 for DPV technique. An optimum medium for DCV at the SPCE was a 0.1 mol l−1 acetate buffer of pH 4.6, an optimum time of stirring of the sample prior to the analysis was 120 s (the attained limit of quantification (LQ) was 8.5×10−6 mol l−1 of NF). For DPV at the SPCE, the optimum medium was an acidic component part of the Britton - Robinson buffer of pH 2.0; the attained LQs were 6.2×10−7 mol l−1 of NF for the concentration range from 1×10−6 to 1×10−5 mol l−1 (at the stirring time of the sample of 120 s) and 2.0×10−7 mol l−1 of NF for the concentration range from 1×10−7 to 1×10−6 mol l−1 (at the stirring time of the sample of 300 s).
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