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The analytical performance of the clay paste electrode and graphene paste electrode was compared using square wave voltammetry (SWV) and cyclic voltammetry (CV). The comparison was made on the basis of a paracetamol (PA) determination on both working electrodes. The influence of pH and SWV parameters was investigated. The linear concentration ranges were found to be 6.0 x 10(-7)-3.0 x 10(-5) and 2.0 x 10(-6)-8.0 x 10(-5) mol L-1 for clay paste electrode (ClPE) and graphene paste electrode (GrPE), respectively. The detection and quantification limits were calculated as 1.4 x 10(-7) and 4.7 x10(-7) mol L-1 for ClPE and 3.7 x 10(-7) and 1.2 x 10(-6) mol L-1 for GrPE, respectively. Developed methods were successfully applied to pharmaceutical formulations analyses. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to characterize ClPE and GrPE surfaces. Clay composition was examined with wavelength dispersive X-ray (WDXRF)., Analytická výkonnost jílových pastových elektrod a grafenových pastových elektrod byla porovnána s využitím square wave voltametrie (SWV) a cyklické voltametrie. Porovnání bylo provedeno na základě stanovení paracetamolu na obou typech elektrod. Byl testován vliv pH a parametrů SWV. Lineární rozsah stanovení pro jílovou pastovou elektrodu byl 6.0 x 10(-7)-3.0 x 10(-5) mol l-1 a 2.0 x 10(-6)-8.0 x 10(-5) mol l-1 pro grafenovou pastovou elektrodu. K charakterizaci povrchů pastových elektrod byla použita SEM a XRF.

The increasing use of pesticides is a major health issue. There is therefore a need for improved analytical methods and more knowledge on the interaction of pesticides with living organisms. Here, we developed the analysis of profluralin in water and soils by cyclic voltammetry, square-wave voltammetry and square-wave adsorptive stripping voltammetry. We also studied the interaction between profluralin and double-stranded DNA. Results of cyclic voltammetric studies indicate that the reduction processes have an irreversible and adsorption-like character, as a possible consequence of the reduction of nitro groups of profluralin. Quantification was found linear from 60 to 800 nmol L-1 with a detection limit of 17 nmol L-1 using square-wave adsorptive stripping voltammetry. Results of interactions with double-stranded DNA from salmon sperm revealed that profluralin forms a complex with DNA by electrostatic binding. Values of Gibbs free energy confirmed that formation of profluralin-DNA complex is spontaneous and favourable., Byla vyvinuta analytická metoda pro stanovení herbicidu profluralin cyklickou voltametrií, square wave voltametrií a adsorptivní square wave voltametrií v půdách a vodě. Byla také studována interakce mezi profluralinem a dvojřetězcovou DNA. Výsledky studie pomocí cyklické voltametrie ukazují, že redukce nitro skupin profluralinu má irreverzibilní charakter a je řízena adsorpcí. Adsorptivní square wave voltametrií byl zjištěn lineární rozsah stanovení od 60 nmol l-1 do 800 nmol l-1 a detekční limit 17 nmol l-1. Bylo zjištěno, že profluralin spontánně vytváří komplexy s dvouřetězcovou DNA z lososího sperma elektrostatickou vazbou.

The use of square wave voltammetry (SWV) and square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode for the determination of flumetralin is presented. Poor separation of two overlapped reduction peaks is significantly improved when hexadecyltrimethylammonium bromide is used as a component of the supporting electrolyte solution (together with BR buffer pH 9.5). The SW technique parameters were investigated and found optimal as follows: frequency 50 Hz, amplitude 40 mV, and step potential 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive voltammetry. The analytical curve was linear for the flumetralin concentration range from 1.0x10(-6) to 1.0x10(-5) mol dm(-3) and from 5.0x10(-9) to 1.0x10(-7) mol dm(-3) for SWV and SWAdSV, respectively. Detection limit of 6.5x10(-10) mol dm(-3) was calculated for accumulation time 60 s at -0.2 V. The repeatability of the method was determined at a flumetralin concentration level equal to 5.0x10(-9) mol dm(-3) and expressed as % RSD = 5.0% (n = 6). The proposed method was applied and validated successfully by studying the recovery of herbicide content in spiked environmental samples., Square wave voltametrie (SWV) a square wave adsorptivní rozpouštěcí voltametrie (SWAdSV) ve spojení s cyklicky obnovitelnou elektrodou ze stříbrného amalgámu byly použity ke stanovení flumetralinu. Špatné rozdělení dvou překrývajících se redukčních píků bylo významně vylepšeno přídavkem cetyltrimethylamoniumbromidu do základního elektrolytu Brittonova-Robinsonova pufru pH 9,5. Byly studovány parametry square wave voltametrie a jako optimální vybrány tyto: frekvence 50 Hz, amplituda 40 mV a potenciál kroku 5 mV. Čas a potenciál akumulace byly studovány pro výběr optimálních podmínek v adsorptivní voltametrii. Kalibrační křivka byla lineární pro koncentrační rozsah flumetralinu od 1.0x10(-6) do 1.0x10(-5) mol dm(-3) pro SWV a od 5.0x10(-9) to 1.0x10(-7) mol dm(-3) pro SWAdSV. Detekční limit 6.5x10(-10) mol dm(-3) byl vypočítán pro čas akumulace 60 s při -0,2 V. Opakovatelnost metody byla určena pro koncentraci flumetralinu 5.0x10(-9) mol dm(-3) a vyjádřena jako relativní směrodatná odchylka RSD = 5 % (n = 6). Navržená metoda byla úspěšně aplikována a validována pomocí výtěžnosti herbicidu ve vzorcích životního prostředí.

The electrochemical reduction of lactofen (LCT) at the glassy carbon (GCE) and silver amalgam film electrode (AMFE) is investigatedin detail by the means of square wave voltammetry (SWV), square wave stripping voltammetry (SWSV) and cyclic voltammetry. The influence of various factors such as supporting electrolyte composition and SW parameters were studied. The AMFE electrode showed an excellent electrochemical activity toward the electro-reduction of LCT, leading to a significant improvement in sensitivity as compared to the glassy carbon electrode.The SWSV detection limits for GCE and AMFE were 285.0nM and 2.0nM, respectively. The applicability of the developed voltammetric method for analysis of tap water and river water is illustrated with spiked samples analysis. Moreover, as lactofen is highly toxic to fish and other aquatic organisms, its interaction with dsDNA isolated from salmon sperm was tested. The intercalative mode of LCT binding to dsDNA was estimated. The heterogeneous rate constants were calculated for the free LCT and the LCT-dsDNA complex. Moreover, LCT-dsDNA complex binding ratio and equilibrium constant were determined. The decrease in the SWV peak current of LCT in the presence of dsDNA was used for the determination of dsDNA., Byla zkoumána elektrochemická redukce lactofenu na elektrodách ze skelného uhlíku a stříbrné filmové amalgámy s využitím square wave, rozpouštěcí square wave a cyklické voltametrie. Stříbrná amalgámová filmová elektroda vykazovala výraznou elektrochemickou aktivitu při redukci lactofenu a zvýšení citlivosti jeho stanovení oproti elektrodě ze skelného uhlíku. Dále byly studovány interakce lactofenu s dvojřetězcovou DNA izolovanou ze spermií lososa.