Dariusz Guziejewski

The Influence of Protonation on the Electroreduction of Bi (III) Ions in Chlorates (VII) Solutions of Different Water Activity

We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, as well as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4− ions. The standard rate constants ks values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nkf = f(E) dependences.

Voltammetric behaviour and quantitative determination of pesticide iminoctadine

Iminoctadine (IOD) was determined in spiked river water samples by square wave voltammetry (SWV) using a cyclic renewable silver amalgam film electrode (Hg(Ag)FE). It was found that the compound can act as an electrocatalyst. In Britton–Robinson buffer at pH 6.5 a signal connected with the catalytic hydrogen evolution reaction was detected at −1.8 V versus Ag/AgCl. Validation of the method was carried out. The LOD and LOQ have been estimated to be 2.6 × 10−9 mol L−1 and 8.5 × 10−9 mol L−1, respectively.

Electrochemical study of the fungicide acibenzolar-s-methyl and its voltammetric determination in environmental samples

The electrochemical behavior of new generation fungicide acibenzolar-s-methyl (S-methyl 1,2,3-benzothiadiazole-7-carbothioate, ASM) on the hanging mercury drop electrode (HMDE) was investigated using square wave adsorptive stripping voltammetry. This method of determination is based on the irreversible reduction of ASM at the HMDE. The well-defined ASM peak was observed at −0.4 V (vs. Ag/AgCl) in BR buffer at pH 2.2. The reduction peak current was proportional to concentration of ASM from 1.0 × 10−8 to 6.0 × 10−8 mol L−1 with detection and quantification limit 3.0 × 10−9 and 1.0 × 10−8 mol L−1, respectively. The applicability of the developed method for analysis of spiked samples of tap water, river water, and soil is illustrated. The effect of adsorption on the mercury electrode was studied in detail using the AC impedance method. Possible interferences with other common pesticides and heavy metal ions were examined. Clarification of the electrode mechanism was made using cyclic voltammetry (CV) technique.

Voltammetric behavior and quantitative determination of ambazone concentrations in urine and in a pharmaceutical formulation

The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about −1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10−9 to 1.0×10−7 mol L−1. The detection and quantification limits were found to be 3.0×10−10 mol L−1 and 1.0×10−9 mol L−1, respectively. The proposed method was successfully applied to ambazone determination in real samples.

Application of the catalytic properties of methionine to the determination of Bi(III) as well in the presence of Cu(II) ions at low levels by square wave voltammetry

ABSTRACT A simple and fast method for the determination of Bi(III) in the presence Cu(II) in non-complexing solution was proposed. The catalytic activity of L-methionine on Bi(III) ions electroreduction as well as lack of this amino acid influence on Cu(II) ions electroreduction process were utilised. The calibration graph of Bi(III) in 4 mol dm−3 chlorate (VII) in the presence of 5 × 10−2 mol dm−3 methionine is linear in the range of concentrations of Bi(III) from 3 × 10−7 to 1 × 10−4 mol dm−3. The detection and quantification limits were found to be 1.53 × 10−7 and 5.12 × 10−7 mol dm−3, respectively. Precision and recovery of the method were investigated by determination of Bi(III).

The effect of homocysteine and homocystine protonation on double-layer parameters at the electrode/chlorates(VII) interface:

In this study, a comparison of the properties of homocysteine and homocystine adsorption at mercury/chlorate(VII) interface was done. The adsorption of homocysteine and homocystine is in fact the adsorption of mercury(II) cysteine thiolate and mercury(I) cysteine thiolate. The differences in the capacity curves result probably from the formation of mercurous thiolate at the mercury surface. It seems that the changes in Ez and γ z values accompanying the change in the amino acid protonation in the basic electrolyte solution, confirm the altered arrangement of the cysteine mercury thiolates on the electrode surface.

Use of isomeric, aromatic dialdehydes in the synthesis of photoactive, positional isomers of higher analogs of o-bromo(hetero)acenaldehydes

Synthesis of the pairs of positional isomers of the title compounds is based on utilization of two isomeric o,o-dibromo dialdehydes and a selective ortho-metallation/Friedel–Crafts cyclization sequence of the corresponding diacetals. Photophysical and electrochemical properties of the new group of fluorescent and photoresistant compounds have also been performed.

Graphene oxide activation with a constant magnetic field

The effect of constant magnetic field strength on activation of sensors modified with graphene oxide monolayers was investigated. The use of constant magnetic field resulted in improved electroanalytical properties of the sensors. It was proven that level of GO activation is clearly related to constant magnetic field strength. Moreover, it was demonstrated that observed phenomenon is stable in time.

First Electrochemical Method of Nitrothal-Isopropyl Determination in Water Samples

The aim of the research was the use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a hanging mercury drop electrode (HMDE) for the determination of nitrothal-isopropyl. It was found that optimal SW technique parameters were frequency, 200 Hz; amplitude, 50 mV; and step potential, 5 mV. Accumulation time and potential were studied to select the optimal conditions in adsorptive stripping voltammetry: 45 s at 0.0 V, respectively. The calibration curve (SWSV) was linear in the nitrothal-isopropyl concentration range from 2.0 × 10−7 to 2.0 × 10−6 mol L−1 with detection limit of 3.46 × 10−8 mol L−1. The repeatability of the method was determined at a nitrothal-isopropyl concentration level equal to 6.0 × 10−7 mol L−1 and expressed as RSD = 5.5% (). The proposed method was successfully validated by studying the recovery of nitrothal-isopropyl in spiked environmental samples.