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Danhel A.,Academy of Sciences of the Czech Republic | Raindlova V.,Czech Institute of Organic Chemistry And Biochemistry | Havran L.,Academy of Sciences of the Czech Republic | Barek J.,UNESCO Laboratory of Environmental Electrochemistry | And 4 more authors.
Electrochimica Acta | Year: 2014

Voltammetric behaviour of novel synthetic multi-redox DNA label N-methyl-4-hydrazino-7-nitrobenzofurazan (NBF), a deoxycytidine monophosphate conjugate with NBF via formylthiophene linker (dCNBFMP), and NBF labeled model short double stranded DNA (dsDNA-NBF) were systematically studied at mercury meniscus modified silver solid amalgam electrode (m-AgSAE) for the first time in this work. Successful enzymatic incorporation of the NBF labeled deoxycytidine triphosphate into the DNA was confirmed and the dsDNA-NBF offered new more positive cathodic signals at -520 mV and -1160 mV, compared to the nucleic acid itself. Used modification resulted in increase of selectivity and sensitivity of the DNA voltammetric determination. Next to the pioneering voltammetric behaviour of all studied compounds at m-AgSAE, electroanalytical methods based on cyclic voltammetry, adsorptive stripping cyclic voltammetry and open circuit transfer stripping cyclic voltammetry were developed for sensitive detection of these (bio)molecules. Furthermore, utilization of variable negative vertex potential and scan rate was also observed and their appropriate selection considerably influenced registered peaks on cyclic voltammograms. These redox processes increased signal response diversity and offered utilization of signal switch on/off technique, as well. Tentative electrochemical reduction mechanisms of the NBF, dCNBFMP and dsDNA-NBF were proposed and discussed, together with possibilities and limitations of the NBF + m-AgSAE system. © 2014 Elsevier Ltd.

Yosypchuk O.,UNESCO Laboratory of Environmental Electrochemistry | Yosypchuk O.,Charles University | Barek J.,UNESCO Laboratory of Environmental Electrochemistry | Barek J.,Charles University | And 2 more authors.
Analytical Letters | Year: 2012

Based on the study of voltammetric behavior of carcinogenic 1-nitropyrene (1-NP), 1-aminopyrene (1-AP), and 1-hydroxypyrene (1-HP), optimum conditions have been found for the determination of these analytes by differential pulse voltammetry (DPV) at a boron-doped diamond film electrode. The optimum medium was methanol-Britton-Robinson buffer (BR buffer) pH 3.0 (70:30) for 1-NP and 1-AP, and methanol-BR buffer pH 5.0 (70:30) for 1-HP. Concentration dependences of the DPV response were measured in the range 1 · 10 -6-1 · 10 -4 mol dm -3 (R = -0.9998) with the limit of detection (LOD) 3 · 10 -7 mol dm -3 for 1-NP, 1 · 10 -7-1 · 10 -5 mol dm -3 (R = 0.9971) with LOD 6 · 10 -8 mol dm -3 for 1-AP, and 1 · 10 -7-1 · 10 -5 mol dm -3 (R = 0.9934) with LOD 1 · 10 -7 mol dm -3 for 1-HP. Simultaneous determination of 1-NP and 1-AP in a mixture was tested in the methanol-BR buffer pH 3.0 (70:30) medium as well. The content of 1-AP in the concentration range from 1 · 10 -6 to 1 · 10 -4 mol dm -3 had no effect on the sensitivity of the determination of 1-NP, and vice versa. Due to the close peak potentials of 1-AP and 1-HP, the direct determination of their mixture using voltammetric methods is impossible. © 2012 Copyright Taylor and Francis Group, LLC.

Zima J.,UNESCO Laboratory of Environmental Electrochemistry | Tinkova V.,UNESCO Laboratory of Environmental Electrochemistry | Wang J.,University of San Diego | Barek J.,UNESCO Laboratory of Environmental Electrochemistry
Collection of Czechoslovak Chemical Communications | Year: 2011

Direct current (DC) voltammetry and differential pulse (DP) voltammetry using a carbon paste electrode (CPE) have been used for the determination of trace amounts of ecotoxic 1,2-diaminoanthraquinone (DAAQ). The limit of determination (LD) of DAAQ for DC voltammetry was 2 × 10 -6 mol l-1, and for DP voltammetry 2 × 10 -7 mol l-1 under the optimized conditions in a mixed Britton-Robinson buffer pH 12 and methanol (1:9) medium. Adsorptive accummulation of the analyte on the surface of CPE decreased the limit of determination to 2 × 10-8 mol l-1 for DP voltammetry. Practical applicability of these newly developed methods was verified on model samples of river water. © 2011 Institute of Organic Chemistry and Biochemistry.

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