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Electrochemical reduction of vanadium(V) complex with cupferron (N‐nitroso‐N‐phenylhydroxylamine), VVO(cupf)2OH, has been studied by polarography in wide potential range to verify the catalytic mechanism of electroreduction of coordinated cupferron ligand. Reduction of the complex was studied in the concentration range from 2 ⋅ 10−5 M to 10−3 M. Depending on the process conditions kinetics of catalytic reduction of coordinated cupferron is either controlled by adsorption step or governed by mixed control of diffusion and chemical reaction. Kinetic parameters of the reduction process are reported. Reduction of VVO(cupf)2OH complex is accompanied by adsorption and autoinhibition phenomena. V(II) ion in the surface bound complex of vanadium with cupferron catalyzes reduction of coordinated cupferronate ligands. In 1 mM solutions, the catalytic reduction of coordinated cupferron ligand shifts to more cathodic potentials due to formation of a monolayer of adsorbed vanadium(III)‐cupferron complexes. Reduction kinetics in the presence of tetraalkylammonium salt is consistent with multilayer cooperative adsorption of anionic vanadium(II)‐cupferron complex and tetraalkylammonium cations. [ABSTRACT FROM AUTHOR]

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)-cupferron complex in the differential pulse mode (detection limit of 1.0 µg L−1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L−1 for Cd (II) and 2.43 µg L−1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO3/H2O2). The following value ranges were evaluated: U (VI) 37.2-150 mg kg−1, Pb (II) 78.3-204 mg kg−1 and Cd (II) 44.1-71.6 mg kg−1. Validation was performed by using the standard reference materials SRM-695 - phosphate fertilizer - and SRM-1643e - water. [ABSTRACT FROM AUTHOR]

Dynamic covalent libraries (DCLs) of quaternary ammonium cations were set up by reversible nucleophilic substitution (SN2′ and SN2) exchange reactions of ammonium salts and tertiary amines. The reactions were conducted at 60 °C to generate thermodynamically and kinetically controlled mixtures of quaternary ammonium compounds and tertiary amines, and were accelerated by using iodide as a nucleophilic catalyst. Microwave irradiation was used to assist the exchange reaction between the pyridinium salts and pyridine derivatives. Finally, experiments towards the generation of dynamic ionic liquids were performed. The results of this study pave the way for the extension of dynamic combinatorial chemistry to nucleophilic substitution reactions. [ABSTRACT FROM AUTHOR]

Based on the interaction of cupferron and lead(II) complex [Cup-Pb(II)] with double-stranded DNA (dsDNA) a new voltammetric method for the detection of DNA was described in this paper. In pH 4.0 HAc-hexamine buffer solution, [Cup-Pb(II)] complex showed a sensitive second order derivative polarographic reductive peak at -0.554 V (vs. SCE). After the addition of dsDNA into [Cup-Pb(II)] mixture solution the reductive peak current decreased with the positive shift of reductive peak potential, which was the typical characteristic of intercalation mode. Under the optimum conditions, the decrease of reductive peak current was directly proportional to the dsDNA concentration in the range from 1.0 to 25.0 mg/L with the linear regression equation as ΔIp″ (nA) = 129.30 + 62.51 C (mg/L) (n = 13, γ = 0.991). The detection limit of 0.90 mg/L (3σ) and the relative standard derivation (RSD) of 2.43% for 10 parallel determinations of 10.0 mg/L dsDNA were found. The method was successfully applied to synthetic samples with good results, and the stoichiometry of dsDNA with [Cup-Pb(II)] complex was calculated by the voltammetic data with the binding number as 2 and the binding constant as 2.82 × 109. [ABSTRACT FROM AUTHOR]

A voltammetric method was developed for zirconium determination as Zr(IV)-cupferron-oxalate-diphenylguanidine complex based on adsorptive accumulation at the HMDE ( Epeak=−0.95 V). The supporting electrolyte was a mixture of acetate/acetic acid (pH 4.6) and ammonium acetate (pH 5.7) solutions. Eads=−0.6 V (vs. Ag/AgCl), tads=400 s, 10 mV s−1 scan rate, and DP mode were the main parameters. The linear range was 0.033 to 3.3×10−9 mol L−1, and the LOD and LOQ ( tads=400 s) were 0.77 and 1.6×10−11 mol L−1, respectively. The method was adequate for seawater samples, although not sufficiently sensitive for surface waters. [ABSTRACT FROM AUTHOR]

The development of a new electrochemical sensor for determination of trace molybdenum, based on cupferron-tetraphenylborate ion-pair drop coated modified screen-printed carbon electrode (Cup-SPCE) is described. The printing inks, printing device, substrate and all used materials for making the sensor were prepared as homemade. Under the optimum conditions, the analytical calibration curve was found bimodal with linear concentration ranges from 5 to 200 ng mL−1 and from 200 to 2000 ng mL−1. The detection limit of the method in the concentration of 5-200 ng mL−1 was found to be 2.5 ng mL−1. The method was successfully applied for the determination of Mo(VI) in drinking water samples. [ABSTRACT FROM AUTHOR]

The effects of the respiratory inhibitor, cupferron, upon respiration, growth and the geotropic reactions of wheat roots were studied. In the minimum concentrations inhibiting respiration, growth is decreased. The positive geotropic reaction is not affected while the negative one is inhibited. In higher concentrations all the processes are inhibited. The peculiar effect on the negative reaction is assumed to take place via an increase in the oxygen concentration caused by the inhibition of respiration. The possibilty of drawing false conclusions in comparing growth and geotropic reaction is discussed. [ABSTRACT FROM AUTHOR]