The electrochemical behavior of Fe(III) in the presence of phytate ligand was investigated by cyclic voltammetry on the polycrystalline gold and mercury drop electrodes in the pH range between 1.5 and 10, and ligand to metal molar ratio from 0 to 20. Complexation of Fe(III) and Fe(II) by phytate ligand (L) reflects in (i) shift of the formal potential E0’ of the Fe(III)/Fe(II) redox couple into the negative direction, and (ii) an increased irreversibility of the redox processes. Change of the formal potential originate from higher stability of the Fe(III)L complex with respect to Fe(II)L complex, however, due to the slow charge transfer control of the redox processes apparent stability constants calculated from voltammetric data may lead to an overestimation of their true values. Irreversible reduction of Fe(III)L to Fe(II)L is diffusion controlled and involves one proton per one electron on both electrodes. Reduction of Fe(III) phytate complex to Fe(II)L depends on the pH and at pH ( 5 proceeds via [FeIIIH5L]4– species, but at higher pH less protonated [FeIIIH3L]6– become the major reacting species. An almost stepwise change of the reduction peak potential for more than 0.8 V into the negative direction around pH 5 indicate that both reactants have quite different stability and/or structure. We predicted that electronic configuration and affinity of Fe(III) ions for the octahedral coordination induce the inversion of phytate ligand from its equatorial to the axial conformation which form more than ten orders of magnitude more stable Fe(III)L complexes. Fe (II)L intermediate generated on the electrode is strongly adsorbed on both gold and mercury electrodes, and totally irreversible reduction of Fe(II)L complex to the Fe metal was observable at mercury electrode as well. From Fe(III/II)L peak analysis on the mercury electrode the cathodic charge transfer coefficient of 0.68 was found, for [FeIIIH3L]6– reacting species the diffusion coefficient of (9.1±0.1) x10–7cm2/s was estimated, and the rate constant k0 of 7.8 x10–5 cm/s was calculated.
COBISS.SI-ID: 1536395203
In the paper fast chromatographic method for separation of lysozyme PEG positional isoforms at low pressure using monoliths is described. Such method can be used for process analytical technology (PAT).
COBISS.SI-ID: 1536812483
A new variable distance weighted zero order connectivity index was used for development of structure-activity relationship for modelling reactivity of OH radical with alkanes and non-conjugated alkenes in the atmosphere. The model was compared with the EPA implemented model in the studied application domain and showed superior prediction capabilities. Further, optimized values of the weights that were used in our model permit some insight into mechanisms that govern the reaction OH + alkane/alkene. The most important conclusion is that the branching degree of the forming radical seems to play a major role in site specific reaction rates. The modeling was performed using MACI, inhouse developed software.
COBISS.SI-ID: 1536789955
In order to perform a risk assesment of chemicals that are introduced in the environment, estimation of their toxicity is crucial. Polychlorinate organic compounds were successfully tested using multiple linear resgression QSAR model. Various structural descriptions were applied for translation of chemical structure into computer readable form.
COBISS.SI-ID: 1536764355
In this work we explore the chemical effects of particulate matter on paper. We exposed paper made of pure cellulose to the environment in different locations in central London, outdoors and indoors, for a period of up to 6 months. We observed higher deposition rates and higher metal concentration outdoors than indoors. Elemental analysis of the deposited particles revealed the presence of some transition metals (Fe, Cu, Cr) that can contribute to the degradation of cellulose fibres through the Fenton reaction. The results suggest that the presence of Fenton metals in PM has a significant effect on the acceleration of the degradation of cellulose.
COBISS.SI-ID: 1536769475