Study of complexes of biologically active compounds with multivalent cations and their interaction with phospholipids and biological membranes. Development of hyphenation of electrochemical methods with mass spectrometry.
Abstract: The coupling of electrospray ionization mass spectrometry (ESI-MS) with an electrochemical (EC) method is a promising technique applicable in electrochemical reaction studies as well as in other analytical fields. The connection of two-electrodes flowing EC cell prior ESI-MS is provided and tested on ferrocene/ferricene system. The base electrolyte used (a mixture of NaClO4 and HClO4) causes particular oxidation of ferrocene to ferricene. Consequently, in ESI-MS spectrum are observed two charged ferricene/ferrocene species: protonated ferrocene (Cp2Fe(II)H)+ and ferricene (Cp2Fe(III))+. In the on-line connection of EC with ESI-MS the ferricene species is electrochemically reduced (in accumulation step of differential pulse anodic stripping voltammetry via insertion of negative potential) to ferrocene species, which is detected as (Cp2Fe(II)H)+ using ESI-MS. The yield of electrochemical reduction of ferricene to ferrocene is almost 30 %, whereas the inserted potential is 1000 mV.
Abstract: Tebuconazole (1) belongs to a class of widely utilized plant fungicides, mostly in vineyards. Consequently, traces of this compound are present in plant tissues, wine as well as in soil. The aim of this study was in situ generation of Cu cations and creation of very stable Cu complexes with 1. The proposed method involves a hyphenation of electrochemistry with electrospray ionization mass spectrometry (ESI-MS), based on the high affinity of 1 for dissolved copper cations. We demonstrate that at appropriate potentials (above 500 mV vs silver reference electrode) Cu cations can be generated in an electrochemical cell, which subsequently form complexes with 1 present in the sample. The resulting complex [Cu(1)]+ as well as its fragment [Cu(1-C4H10)]+ are then detected with online coupled ESI-MS. This finding is useful for a creation of an analytical method based on the detection of trace amounts of 1 in complex matrices (e.g., soil solution), in which the analyte may be spread among various species.
Abstract: The transport of cadmium and of copper ions across the artificially prepared model phospholipid (PL) membranes on the polycarbonate supports was studied in the present manuscript. The processes were investigated in the presence of selected low molecular weight organic acids (LMWOAs) (malic acid (MA), oxalic acid (OA) and citric acid (CA)), which substantially affect the transport conditions in the rhizosphere. It was found that the transport was influenced by presence/absence of ionophores calcimycin and by the value of pH. Electrochemical impedance spectroscopy (EIS) was used to monitor the formation, the stability, and qualitatively the transporting process across the supported phospholipid bilayers (SPLBs), whereas voltammetric methods were applied for quantitative and qualitative characterization of the species (ions and complexes), which are transferred across the SPLBs. The structures of the formed complexes were investigated using mass spectrometry.
Abstract: Tebuconazole (Teb) as a systemic fungicide amounts a potential risk for environment even in very low concentrations. The voltammetric behavior of Teb was investigated using the newly developed mercury meniscus-modified copper solid amalgam electrode (inner diameter 1.5 mm). Differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were utilized for these purposes. The reaction mechanism was investigated using CV and elimination voltammetry with linear scan (EVLS). The optimum conditions for DPV determination of Teb were found in Britton-Robinson buffer/methanol (1:1, v/v) of pH 6.4, initial potential and accumulation potential Ein=Eacc=+400 mV vs. Ag/AgCl/3M KCl, scan rate 20 mV s-1. Applying the prolonged accumulation time (60 s), the limit of detection 0.2 µmol L-1 was reached. The applicability of the developed method for determination of Teb in two samples of real soil solutions was verified.
Abstract: The aims of the paper were as follows: (1) to assess the applicability of speckled alder for pioneer stands on the mountainous clear-cut tracts and (2) to evaluate the effects of slow-release fertilizer on the survival and growth of speckled alder under harsh environmental conditions. On the basis of seven-year results we can presume that speckled alder is a convenient pioneer species that can be cultivated on harsh mountain sites where the climatic extremes need to be alleviated and a layer of surface humus renewed. The initial slow-release fertilization is, nonetheless, highly desirable. As contrasted to the control the surface and planting hole applications of amendment reduced the total seven-year mortality rate by 9.5% and 20.1%, respectively, and the periodic annual height increment (2003â2009) was promoted by 47% and 59%, respectively. Analogous results were obtained when the values of basal stem diameter and crown diameter were compared. As for the method of application, the placement of the slow-release amendment in the planting holes seems to be more efficient mainly in terms of survival promoting. The surface application is, nonetheless, less laborious and also yielded satisfactory results.
Abstract: Electrospray ionization was used as a technique for the characterization of the interactions between cadmium(II) ions and malic acid (1) in aqueous solution. Particular attention was paid to the nature of the species formed, which generally correspond to complexes of CdX+ cations with neutral malic acid, where X either is the counterion of the metal salt used as a precursor (i.e. X = Cl, I) or corresponds to singly deprotonated malic acid. In pure water solutions, also highly coordinated complexes [Cd(1 H)(1)2]+ and [CdCl(1)2]+ were detected, whereas the most abundant complexes detected in a sample of soil solution were: [Cd(1 H)(1)]+ and [CdCl(1)]+. With respect to possible application in environmental analysis, the effects of (i) metal salts present in solution, (ii) modest mineralization, and (iii)the matrices of real soil solutions were probed. While the presence of other metals leads to additional complexes, the characteristic species containing both cadmium(II) and malic acid can still be detected with good sensitivity.
Abstract: The formation of complexes between tebuconazole (Teb) and cadmium in simplified model solutions as well as soil solutions was studied using electrospray ionization mass spectrometry. Teb and cadmium form two types of complexes with the general formulas [Cd(Teb)n]2+ (n = 1â4) and [CdI(Teb)m]+ (m = 1â3), where iodine corresponds to the counterion used. The most intense Teb/cadmium complex is [CdI(Teb)2]+, and the most stable one is [Cd(Teb)(Teb â H)]+. Another detected complex, the dication [Cd(Teb)4]2+, was considered as the origin complex for the iodine-free complexes and was found in a sample prepared from forest soil solution naturally contaminated with cadmium ions.
Abstract: This study presents a new analytical approach for the determination of heavy metals complexed to low-molecular-weight-organic acids in soil solutions, which combines the sensitivity of differential pulse anodic stripping voltammetry (DPASV) with the molecular insight gained by electrospray ionization mass spectrometry (ESI-MS). The combination of these analytical methods allows the investigation of such complexes in complex matrixes. On the voltammograms of the soil solutions, in addition to the expected complexes of oxalic acid with cadmium and lead, respectively, also peaks belonging to mixed complexes of cadmium, lead, and oxalic acid (OAH2) were observed. In order to verify the possible formation of complexes with OAH2, aqueous solutions of OAH2 with traces of Cd(II) were investigated as model systems. Signals corresponding to several distinct molecular complexes between cadmium and oxalic acid were detected in the model solutions using negative-ion ESI-MS, which follow the general formula [Cdn(X,Y)(2n+1)]-, where n is the number of cadmium atoms, XÂ =Â Cl-, and YÂ =Â OAH-. Some of these complexes were also identified in the ESI mass spectra taken from the soil solutions.
Abstract: The stabilization of lecithin layer physically adsorbed on the interface between two immiscible electrolyte solutions (ITIES) using addition of Yb3+ to the aqueous phase was studied using cyclic voltammetry. Stability of this layer was evaluated according to the time of the layer formation; the optimal time amounted to 180 s. The stability of the layer as a function of the potential applied on the system during the layer formation was investigated. The behavior of the monolayer during the layer polarization was studied by the facilitated K+ transport using dibenzo-18-crown-6. The stoichiometry of Yb/anion/lecithin complexes was investigated using electrospray ionization mass spectrometry (ESI-MS).
Abstract: Electrospray ionization mass spectrometry (ESI-MS) is used to probe the complex formation between tebuconazole (1) and copper(II) salts, which both are commonly used fungicides in agriculture. Experiments with model solutions containing 1 and CuCl2 reveal the initial formation of the copper(II) species [(1)CuCl]+ and [(1)2CuCl]+ which undergo reduction to the corresponding copper(I) ions [(1)Cu]+ and [(1)2Cu]+ under more drastic ionization conditions in the ESI source. In additional experiments, copper/tebuconazole complexes were also detected in samples made from soil solutions of various origin and different amount of mineralization. The direct sampling of such solutions via ESI-MS is thus potentially useful for understanding of the interactions between copper(II) salts and tebuconazole in environmental samples.
Abstract: The knowledge of thermodynamic balances among metals species in environmental matrixes can help in the understanding of processes related to the environmental stress of plants and in the design of suitable phytoremediation strategy. In these processes, low-molecular-weight organic acids (LMWOAs) play a very important role, and therefore the determination of metals species with LMWOAs is of current research interest. Electrochemical techniques available for the trace analysis of metal ions are suitable for speciation studies including the computation of stability constants and the determination of the stoichiometries from the properties of voltammograms/polarograms (pseudopolarograms). Additionally, labile and inert (stable) complexes can be distinguished by several electrochemical methods. A new approach is the hyphenation of electrochemistry (EC) with electrospray ionization mass spectrometry (ESI-MS), which provides assistance to the description of the electrochemical behavior of the complexes as far as both thermodynamic aspects and kinetic properties of metals complexes with LMWOAs are concerned.
Abstract: Air, waters and soils has being in increased levels contaminated with various metals, inorganic or organic compounds (partly products of human activity). To secure the normal processes in the living (plant or animal) cells, it is necessary to realize transport of various inorganic and organic compounds (nutrients, etc.), across the cell membrane into or out of the cells or various sub-cellular structures. Not only the useful and usual metabolic compounds are transported into the cells, across the membranes; however, the above mentioned undesired ions, compounds and particles, which are connected with pollution of human environment, are participated in the transporting processes. They are based on many principles, which we intend to study using electrochemical methods (electrochemical impedance spectroscopy, voltammetry, conductometry, patch-clamp techniques etc.). In this contribution, there are described the results of experiments realized on model of supported membranes and some ways of preparation of protoplasts, which would be suitable for patch clamp studies of the charged particles transport. The anodic stripping voltammetry, cyclic voltammetry and related methods were successfully applied for determination and characterization of heavy metal complexes with low-molecular-weight organic acids (LMWOAs) in soil solutions sampled from rhizosphere and bulk soil. All these experiments help us to explain the transporting processes of heavy metals across the real membranes of protoplasts.
Notes: Cited By (since 1996): 1 xD;Export Date: 2 July 2011 xD;Source: Scopus xD;Language of Original Document: English xD;Correspondence Address: Navrátil, T.; Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of AS CR, v.v.i., Dolejškova 3, 182 23 Prague 8, Czech Republic; email: tomas.navratil@jh-inst.cas.cz
Abstract: In experiments with willow planted in cadmium- or lead-contaminated Knopp nutrient solutions, the ability of willow and chelex gel in the diffusive gradient in a thin film (DGT) unit to absorb these elements was observed and compared. A method to compare the accumulated amount of metals by the willow and the sorbed amount of metal onto the DGT unit was designed. The accumulated/sorbed amount of metals was recalculated to the same units (mu g cm(-2) day(-1)). The study of Cd(Pb) dynamic uptake by willow showed an exponential decrease of metal content in the exposure solution. The willow planted in the Knopp nutrient solution accumulated Cd(Pb) less than did the DGT unit in the same matrix. The willow planted in the soil/water system accumulated more lead than did the willow in a lead-contaminated aquatic system nor did the DGT unit in the nitrate matrix. The willow further accumulated lead from the soil/water system due to the active co-uptake of nutrients and lead. The DGT technique was considered as very good comparative method to measure heavy metals plant uptake. This technique is suitable for use in water as well as in soil systems.
Abstract: Current university education is characterized by mass education and student anonymity even though individual education is much more effective. The Student usually depends on self-education though it is limited. This report deals with the ways and means that can be used by a university teacher for student motivation to self-education, Such as e-learning programs and blended learning.
Notes: ISI Document Delivery No.: 437WR xD;Times Cited: 0 xD;Cited Reference Count: 15 xD;Dytrtova, Jana Jaklova Dytrtova, Radmila Jakl, Michal Tlustos, Pavel xD;Chemicke listy xD;Prague 6
Abstract: Low-molecular-weight organic acids (citric, acetic and oxalic). which are common in soil solutions, decrease accumulation and diffusion flow of cadmium. The flows depend on the amount and type of organic acid in solution. The order of focused. acids according to the degree of diffusion retardation is: acetic < oxalic < citric acid. The relative diffusion flow (F-r) was obtained as the gradient of the time dependences of real amounts of accumulated Cd. From F-r and real flow of free Cd, the kinetic flow was calculated, which characterizes the retardation impact of the acids on cadmium diffusion.
Notes: ISI Document Delivery No.: 450SJ xD;Times Cited: 2 xD;Cited Reference Count: 27 xD;Dytrtova, Jana Jaklova Jakl, Michal Kolihova, Dana Miholova, Daniela Tlustos, Pavel xD;Chemicke listy xD;Prague 6
Abstract: The Cd and Pb complexes with oxalic (OA) and citric acid (CA) were detected in model and soil solutions using cyclic and stripping voltammetry. A mixed complex consisting of Cd, Pb, and OA was found; its peak potential varied from -582.0 to -542.5 mV (vs. Ag/AgCl/KCl(3 mol L-1)). For mixed complex formation, the presence of PbOH+ species and Cd 21 in oxalic acid solution was necessary. Only the 'simple' complexes of CA with Pb and Cd were found in the model solution. The existence of all investigated metal complexes is confined to neutral pH range. ne mixed complex was also found in real soil solutions.
Abstract: In the soil solutions obtained in situ with suction cups from soils (Cambisol and Fluvisol) of pot experiment with Salix smithiana Smith, Lolium perenne L. and Thlaspi caerulescens J. & C. Presl heavy metals species (Cd, Pb and Cu) were assayed by differential pulse anodic stripping voltammetry and diffusive gradient in thin films. Prediction of accumulation performed best at free metal ion concentrations in unchanged pH (in 10â3 mol Lâ1 NaClO4 base electrolyte). The speciation provided by differential pulse anodic stripping voltammetry according to pH can provide a detailed description of the soil solution matrix. The concentration of free metals in unchanged pH represents a small part of the total content and varied from 0.04 to 0.75% with two exceptions found for accumulating plants (the content of Cd2+ in the soil solution from T. caerulescens was about 6% and the content of Cu2+ in the soil solution from S. smithiana was about 30%). The available concentration as determined by diffusive gradient in thin films was not in correlation with the heavy metals concentration in plant biomass.
Abstract: Tebuconazole is one of the most utilized triazole pesticides in agriculture. Its stability is highly affected by complexation with metals. Moreover, it creates more or less stable complexes with essential elements that become unavailable to plants. In the system with overabundant tebuconazole, an inert (very stable) complex with Zn was found. Elimination voltammetry with linear scan was used for revealing of the electrode processes on the mercury surface. The relatively slow kinetically controlled step in tebuconazole/Zn complex formation indicates the great ability of Zn-tebuconazole system to react with more ligands. Therefore, multiligand Zn-tebuconazole complexes with other ligands are expected in the nature.
Abstract: The hyphenation of an electrochemical cell prior to mass spectrometer with electrospray ionization allows studying of products and/or of intermediates of electrode reactions. The measurement is realized in a flowing system. The flow rate of the sample markedly influences the MS signal intensity of the product. The calculated optimum value for the electrochemical cell with the sweep volume 0.72 µL is in the range from 0.4 to 0.5 mL h-1. The experimental optimal value is 0.45 mL h-1. The optimization of the flow rate has to be provided individually for each product, because the intensity also depends on the rate of the electrode reaction and product stability.
Abstract: The coupling of ESI-MS with two-electrodes flowing cell was provided and tested on ferrocene system. The oxidation potential of ferrocene was 430 mV in Pt/Ag electrode system. The bis-coordinated ferrocene complex with base electrolyte (NaClO4) was found using DPASV provided in different accumulation potentials and its analogy was also observed as protonated cation in mass spectra. The impact of inserted accumulation potential on mass spectra was also studied; the inserted potential changes the natural pattern of ferrocene.
Notes: Dytrtova, Jana Jaklova Jakl, Michal Schroeder, Detlef xD;Proceedings Paper xD;31st Modern Electrochemical Methods xD;May 23-27, 2011 xD;Jetrichovice, CZECH REPUBLIC xD;Strizovicka 19, Usti nad Labem, 400 01, Czech Republic
Abstract: The stability and stoichiometry of leading complex in the model system of copper nitrate and tebuconazole (Teb) were evaluated. The successive formation constant for bis-coordinated Cu-Teb species (involved in peak with potential approx. -250 mV) was measured; β0 = 7.61±0.10. The pseudopolarographic measurement indicated the consecutive loss of NO3- group and Cu reduction in more negative accumulation potentials. The structure of an original bis-coordinated species [Cu(II)NO3(Teb)2]+ was calculated.
Notes: Jakl, Michal Dytrtova, Jana Jaklova Schroeder, Detlef xD;Proceedings Paper xD;31st Modern Electrochemical Methods xD;May 23-27, 2011 xD;Jetrichovice, CZECH REPUBLIC xD;Strizovicka 19, Usti nad Labem, 400 01, Czech Republic
Abstract: The combination of DPASV with ESI-MS allows a reliable detection of metal complexes with small organic ligands. The request to exact molecular mass is essential to stoichiometry design simultaneously with low concentration of the analyte in most of biological matrixes. By the analysis of model solution consisting of Cd(NO3)(2) and oxalic acid (OAH(2)) these structures were identified: [Cd(OAH(2))(H2O)(2)](+), [Cd(OAH(2))(H2O)(3)](+), and [Cd(OAH(2))(H2O)(2)(CH3OH)](+). They were also found in soil solution.
Notes: ISI Document Delivery No.: BRL50 xD;Times Cited: 0 xD;Cited Reference Count: 13 xD;Jakl, Michal Dytrtova, Jana Jaklova Tlustos, Pavel xD;Proceedings Paper xD;30th Modern Electrochemical Methods xD;May 24-28, 2010 xD;Jetrichovice, CZECH REPUBLIC xD;Strizovicka 19, usti nad labem, 400 01, czech republic
Abstract: Electrochemical and mass spectrometric approaches for the detection of metals species with organic ligands are compared. Advantages of the connection of electrochemistry with mass spectrometry are discussed.
Notes: ISI Document Delivery No.: BRL50 xD;Times Cited: 0 xD;Cited Reference Count: 20 xD;Dytrtova, Jana Jaklova Jakl, Michal Schroeder, Detlef xD;Proceedings Paper xD;30th Modern Electrochemical Methods xD;May 24-28, 2010 xD;Jetrichovice, CZECH REPUBLIC xD;Strizovicka 19, usti nad labem, 400 01, czech republic
Abstract: The Cd and Pb complexes with oxalic (OA) and citric acid (CA) were detected in model and soil solutions using cyclic and stripping voltammetry. A mixed complex consisting of Cd, Pb, and OA was found; its peak potential varied from -582.0 to -542.5 mV (vs. Ag/AgCl/KCl(3 mol L-1)). For mixed complex formation, the presence of PbOH+ species and Cd 21 in oxalic acid solution was necessary. Only the 'simple' complexes of CA with Pb and Cd were found in the model solution. The existence of all investigated metal complexes is confined to neutral pH range. ne mixed complex was also found in real soil solutions.
