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Voltammetric Determination of Warfarin at a Screen-Printed Carbon Electrode
Žužičová, Victória ; Vyskočil, Vlastimil (advisor) ; Dejmková, Hana (referee)
In this Bachelor Thesis, the electrochemical behaviour of the drug warfarin sodium was studied at a screen-printed carbon electrode (SPCE) using DC voltammetry (DCV) and differential pulse voltammetry (DPV). The dependence of the voltammetric behaviour of the substance on the pH of the medium was studied in Britton-Robinson buffer (BR buffer) in the pH range of 2.0−12.0. A pH of 7.0 was chosen as the optimum pH for both voltammetric techniques. A repeatability of 3.8% for DCV and 4.3% for DPV was determined for the selected pH. Calibration dependence was monitored under the selected optimal conditions in the concentration range 2∙10−6 to 1∙10−4 mol∙dm−3 . The limit of detection (LOD) was determined to be 1.05∙10−6 mol∙dm−3 for DCV and 2.59∙10−7 mol∙dm−3 for DPV. The limit of quantification (LOQ) was 3.50∙10−6 mol∙dm−3 for DCV and 8.62∙10−7 mol∙dm−3 for DPV. These newly developed methods were used for the determination of the active ingredient in the pharmaceutical formulation Warfarin Orion 5 mg. The values measured by voltammetric methods were compared with those obtained by spectrophotometric measurements. Key words Electrochemistry, Warfarin, Anticoagulants, Direct Current Voltammetry, Differential Pulse Voltammetry, Screen-Printed Carbon Electrode
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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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