Free Ion Concentration Research Articles

Revised application of copper ion selective electrode (Cu-ISE) in marine waters: A new meta-calibration approach

Copper (Cu) is a bio-essential trace element that is of concerns due to its potential toxicity at concentrations commonly encountered in coastal waters. Here, we revisit the applicability of Cu(II) ion selective electrode (Cu-ISE) based on a jalpaite membrane for the measurement of Cufree in seawater. At high total Cu concentration (>0.1 mM), (near)Nernstian slope was obtained and determination of Cufree down to fM levels was possible. However, this slope decreases with decreasing total Cu concentration (e.g. 7 mV/decade at 15 nM total Cu) making the use of a common single calibration approach unreliable. To solve this problem, we carried out several calibrations at different levels of total Cu (15 nM - 1 mM) and ethylenediamine (EN: 5 μM - 15 mM) and fitted the calibration parameters (slope and intercept) as a function of total Cu using the Gompertz function (a meta-calibration approach). The derived empirical equations allowed the determination of Cufree at any total Cu concentration above 20 nM (determination of Cufree at lower total Cu levels is prevented by the dissolution of the electrode). We successfully tested this meta-calibration approach in UV digested seawater in presence of a synthetic ligand (EN), isolated natural organic matter (humic acid, HA) and in a natural estuarine sample. In each case, our meta-calibration approach provided a good agreement with modeled speciation data (Visual MINTEQ), while standard single approach failed. We provide here a new method for the direct determination of the free Cu ion concentration in seawater at levels relevant for coastal waters.

Performance of Chlorella Vulgaris Exposed to Heavy Metal Mixtures: Linking Measured Endpoints and Mechanisms.

Microalgae growth inhibition assays are candidates for referent ecotoxicology as a fundamental part of the strategy to reduce the use of fish and other animal models in aquatic toxicology. In the present work, the performance of Chlorella vulgaris exposed to heavy metals following standardized growth and photosynthesis inhibition assays was assessed in two different scenarios: (1) dilutions of single heavy metals and (2) an artificial mixture of heavy metals at similar levels as those found in natural rivers. Chemical speciation of heavy metals was estimated with Visual MINTEQ software; free heavy metal ion concentrations were used as input data, together with microalgae growth and photosynthesis inhibition, to compare different effects and explain possible toxicity mechanisms. The final goal was to assess the suitability of the ecotoxicological test based on the growth and photosynthesis inhibition of microalgae cultures, supported by mathematic models for regulatory and decision-making purposes. The C. vulgaris algae growth inhibition test was more sensitive for As, Zn, and Pb exposure whereas the photosynthesis inhibition test was more sensitive for Cu and Ni exposure. The effects on growth and photosynthesis were not related. C. vulgaris evidenced the formation of mucilaginous aggregations at lower copper concentrations. We found that the toxicity of a given heavy metal is not only determined by its chemical speciation; other chemical compounds (as nutrient loads) and biological interactions play an important role in the final toxicity. Predictive mixture effect models tend to overestimate the effects of metal mixtures in C. vulgaris for both growth and photosynthesis inhibition tests. Growth and photosynthesis inhibition tests give complementary information, and both are a fast, cheap, and sensitive alternative to animal testing. More research is needed to solve the challenge of complex pollutant mixtures as they are present in natural environments, where microalgae-based assays can be suitable monitoring tools for pollution management and regulatory purposes.

PROTEIN COMPOSITION AND NUTRITIONAL MILK VALUE OF COWS OF UKRAINIAN BLACK-AND-WHITE DAIRY BREED WITH DIFFERENT GENOTYPES OF CAPA-CASEIN (CSN3)

The article presents the results of studies of protein composition and nutritional milk value of Ukrainian Black-and-White dairy cows with different genotypes of kappa-casein. It was found that the milk of cows with the BB genotype contained more total protein by 0.41 and 0.28 %, the mass fraction of protein (Pro Total) – by 0.37 and 0.25 %, with a probable advantage over the protein content (casein) – by 0.46 and 0.29 % (p≤0.001) and the total amount of casein and globulin – by 0.39 and 0.27 % (p≤0.001) against analogs with genotypes AA and AB. There are differences in the chemical composition and physicochemical properties of milk. In particular, the difference in mass fractions of lactose and dry matter in milk between cows with the genotype BB and AA and AB was respectively 0.16 % (p≤0.001) and 0.11 % (p≤0.01) and 0.64 % (p≤0.001) and 0.37 % (p≤0.01). No less valuable in terms of mass fraction of dry matter was the milk of cows with genotype AB, in which the growth of this indicator against animals with genotype AA was at the level of 0.28 % with a statistically significant difference between them (p≤0.01). Freezing point and density as marker criteria that characterizing the presence of falsification were practically unchanged and did not exceed the permissible norms and amounted to 0.551–0.553 °С and 1028.04–1028.45 kg/m3. The content of somatic cells in the milk of cows of different genotypes of kappa-casein was within the permissible level according to the state standard, which indicates the absence of mastitis. Cows with genotype AA had an increased level of titrated acidity and concentration of free hydrogen ions (p≤0.01 – p≤0.001) against analogs with genotypes AB and BB. However, in general, the hydrogen pH of the milk of cows of all groups had a weakly acidic environment, the values of which ranged from 6.66 units. pH in cows with genotype BB up to 6.71 units. pH – in animals with genotype AA.

Influence of organosulphur additives on autocatalytic copper thin film deposition

This article reports the effect of organosulphur additives such as 2-Mercaptobenzothiazole and 2-Benzothiophene on electroless copper bath. Trace quantity of biodegradable methanesulphonic Bronsted acid was used to develop an ecofriendly electroless bath. Toxic free natural polyhydroxylic complexing agent, Xylitol, Glyoxylic acid, an excellent reducing agent and to control free metal ion concentration, pH modifier, Potassium hydroxide were used. 1 ppm and 10 ppm concentration of organosulphur additives were optimized and analyzed at 45 °C at a pH of 13.0 ± 0.25. Inhibiting and accelerating effect of organosulphur additives depends upon throwing power, thickness uniformity, surface tension, grain structure control and deposit characteristics. The physical parameters were calculated by weight gain and gravimetric methods. Corrosion kinetics and electrochemical properties of ecofriendly electroless bath were analyzed by cyclic voltammetry and the Tafel plot. Surface morphology and structural property of pure copper deposits were investigated by scanning electron microscopy and atomic force microscopic methods.

ВДОСКОНАЛЕННЯ МЕТОДИКИ ВИЗНАЧЕННЯ ВМІСТУ ПЕРОКСИДУ ВОДНЮ В АНТИСЕПТИЧНИХ ПРЕПАРАТАХ

It was investigated methods for determining the content of hydrogen peroxide in antiseptic drugs. It is important to improve the quality control of hydrogen peroxide in disinfectants and antiseptics both by improving the technical characteristics of existing measuring instruments and by inventing new methods and means of quality control, namely the use of potentiometric analyzers (sensors). Automatic analysis tools were widely used, which are based on the application of various correlations between the concentration and physicochemical properties of hydrogen peroxide. It was investigated the cost of their manufacture for industrial applications, important criteria for comparing automatic analyzers, the price of further maintenance, selectivity to a particular component, time , and accuracy of analysis. It was considered potentiometric analyzers (sensors) in which enzyme-catalyzed reactions were used to determine the composition of the compound. It was considered hydrogen peroxide control agents which identified that have good performance and metrological characteristics and can also be used as electrodeactive substances for the determination of peroxide in cosmetics and antiseptics. It was considered among all methods of analysis of the concentration of hydrogen peroxide both in the laboratory and for continuous or periodic measurements, titration, oximetry, with the use of catalysts, etc. The operation of potentiometric analyzers has been studied, which was based on the relationship between the effective concentration of free ions of the analyte in solution and the potential of a special indicator electrode. The potential of each electrode was described through the Nernst equation and a typical titration curve was observed, which indicates the possibility of optimal practical use of this potentiometric sensor with the selected electrode scheme. Key words: determination of content, hydrogen peroxide, potentiometric sensors, electrodes, drug Ladoxin

Evaluation of Soil Ameliorants on Immature and Mature Oil Palms in Acidic Peat

Although peat soil has a low pH range of 3.2 to 3.8 units, it remains unclear whether this is a major constraint to oil palm cultivation, as the cultivar is known to tolerate fairly high levels of acidity without any serious adverse effects. Earlier work on liming and acidity correction has often given conflicting and sometimes, even negative results. In view of the latter, two trials were established to evaluate a number of soil ameliorants and their impact if any, on the growth and yield of newly planted and young mature palms in deep acidic peat. This paper summarises results over a 7- year evaluation period. Of the four ameliorants evaluated on newly planted seedlings in trial no.1, limestone dust (LSD) was the most effective in correcting acidity, raising the soil pH from 3.6 to 5.4 - 6.1 units in the top 30 cm of soil. Despite the significant improvement in soil pH, no advantage in nutrient uptake, palm growth and fresh fruit bunch (FFB) yield was recorded over unlimed control plots. In contrast, oil palm bunch ash (BA), eucalyptus fly ash (EFA) and paddy husk ash (PHA) had a smaller impact on soil acidity, but increased FFB yield from 2 per cent to 9 per cent, of which BA was the most effective, especially at the higher rate of application (9.0 kg/palm/year). One negative aspect of acidity amelioration is its impact on peat subsidence. Being highly caustic, application of LSD and BA accelerated decomposition and mineralisation of the peat, increasing subsidence rates by as much as 1.0 cm per annum. In trial no.2 which evaluated two potash sources [muriate of potash (MOP) and BA] on young mature palms, only annual applications of BA significantly improved soil pH, requiring up to 9.0 kg per palm per year to improve and maintain top soil pH above 5.0 units. BA was also superior to MOP in improving soil fertility, particularly the levels of exchangeable potassium, calcium and magnesium and also significantly reduced the concentration of free aluminium ions and aluminium saturation to low or negligible levels. Although BA ameliorated soil acidity and significantly improved soil fertility, no significant differences in FFB yield were recorded between BA and MOP. With MOP, response to fertiliser inputs was linear, highest yield being achieved with 6.0 kg per palm per year. In contrast, no significant differences were recorded between the different BA rates applied, with 4.50 kg per palm per year producing the same yield response as the highest rate of 11.25 kg per palm per year. For peat soil, BA appeared to be the more efficient K source, as it could attain the same yield as MOP, but at lower K inputs. As peat is reported to be very deficient in silica, it is suspected that any positive responses elicited by application of ash products (which have high silica content) could be a response to silica rather than correction in soil acidity. However, as no soil, foliar and product analysis was carried out for silica content in both trials, the latter will remain a hypothesis until proven otherwise. Trials are currently underway to evaluate the impact of silica on oil palm growth and yield in peat soils. Keywords: Acidity, bunch ash, oil palm, peat, soil amelioration.

Proton Competition and Free Ion Activities Drive Cadmium, Copper, and Nickel Accumulation in River Biofilms in a Nordic Ecosystem

Biofilms can be used as a biomonitoring tool to determine metal bioavailability in streams affected by mining and other anthropogenic activities. Surface water and biofilm were sampled over two years from rivers located in the vicinity of a mine located in a Nordic ecosystem (Nunavik, Quebec). Biofilm metal content (Cd, Cu, and Ni) as well as a variety of physicochemical properties were determined to examine relationships between metal accumulation and water quality. Among the three metals of interest, copper and nickel had the highest levels of accumulation and cadmium had the lowest. When considering the exposure levels, nickel was the most abundant metal in our sampling sites. Both exposure and accumulation levels were consistent over time. Biofilm metal content was highly correlated to the ambient free metal ion concentration for sites of circumneutral pHs for all three metals. When the surface water pH was below 6, biofilm metal content was much lower than at other sites with similar aqueous metal concentrations of exposure. This apparent protective effect of decreasing pH can be explained by proton competition with dissolved metals for uptake binding sites at the surface of the organisms within the biofilm as described by the Biotic Ligand Model principles. The relationships obtained for Cd and Cu were overlapping those observed in previous publications, indicating strong similarities in metal accumulation processes in biofilms over very large geographical areas. Although more data are needed for Ni, our results show that biofilms represent a promising metal biomonitoring tool.

Broadband dielectric spectroscopy for monitoring temperature-dependent chloride ion motion in BiOCl plates

The dielectric properties and electrical conduction mechanism of bismuth oxychloride (BiOCl) plates synthesized using chloramine-T as the chloride ion source were investigated. Thermally-activated structure rebuilding was monitored using broadband dielectric spectroscopy, which showed that the onset temperature of this process was 283 K. This rebuilding was related to the introduction of free chloride ions into [Bi2O2]2+ layers and their growth, which increased the intensity of the (101) diffraction peak. The electrical conductivity and dielectric permittivity were related to the movement of chloride ions between plates (in the low-frequency region), the interplanar motion of Cl− ions at higher frequencies, vibrations of these ions, and charge carrier hopping at frequencies above 10 kHz. The influence of the free chloride ion concentration on the electrical conductivity was also described. Structure rebuilding was associated with a lower concentration of free chloride ions, which significantly decreased the conductivity. According to the analysis, the BiOCl plate conductivity was related to the movement of Cl− ions, not electrons.

Free-standing, high Li-ion conducting hybrid PAN/PVdF/LiClO4/Li0.5La0.5TiO3 nanocomposite solid polymer electrolytes for all-solid-state batteries

The free-standing PAN/PVdF/LiClO4/Li0.5La0.5TiO3 nanocomposite solid polymer electrolytes have been prepared by solution casting technique. The thermal stability of composite solid polymer electrolytes is evaluated by TG/DSC analysis, which reveals that the filler incorporated composite samples exhibit high thermal stability up to 500 °C. The XRD analysis demonstrated that the Li0.5La0.5TiO3 nanoparticles significantly reduced the crystallinity of the hybrid PAN/PVdF/LiClO4 polymer films. The FTIR spectra of PAN/PVdF/LiClO4/Li0.5La0.5TiO3 composites show the vibrational band of –CN stretching, CF2 asymmetric stretching, and Ti-O-La stretching which confirmed the complexation between polymer host matrices and Li0.5La0.5TiO3 nanoparticles. The 10 wt% Li0.5La0.5TiO3 nanoparticles embedded PAN/PVdF/LiClO4 solid polymer electrolyte possessed an excellent ionic conductivity of 1.43 × 10−3 S cm−1 at room temperature, which is far better than the filler-free samples (~ 10−5 S cm−1). The incorporation of Li0.5La0.5TiO3 nanoparticles into the PAN/PVdF/LiClO4 polymer electrolyte improves the concentration of free mobile lithium ions and develops Li-ion conduction channels within the crystalline framework. The PAN/PVdF/LiClO4/Li0.5La0.5TiO3 (10 wt%) composite electrolyte exhibited high thermal stability, good discharge capacities of 122, 105, 94, and 80 mAh g−1 at 0.1, 0.5, 1, and 2C rates, and good cycling stability.

Research on the Influence of Carbonation on the Content and State of Chloride Ions and the Following Corrosion Resistance of Steel Bars in Cement Paste

In this paper, the changes of free chloride ion concentration and bound chloride concentration in cement paste with different total and proportion of mineral admixtures under carbonation were studied. Moreover, the following corrosion resistance of steel bars buried in cement paste under carbonation was researched by testing the electrical resistance and alternating current (AC) impedance spectroscopy of reinforced cement paste. Results indicated that fly ash and granulated blast furnace slag powder with the content less than 20% by mass ratio of total binder hindered the solidification of chloride ions in cement-based materials, and blast furnace slag powder with the content higher than 20% promoted the solidification of chloride ions in cement paste. The carbonation effect was able to decrease the amount of solidified chloride ion and increase the amount of free chloride ions leading to accelerating the corrosion of reinforcement. Meanwhile, the blast furnace slag powder with the content higher than 20% could effectively promote the corrosion resistance of steel bars.

Service Life Modeling of Concrete with SCMs Using Effective Diffusion Coefficient and a New Binding Model

This paper presents a new algorithm that predicts the service life of concrete contains supplementary cementitious materials, SCMs, and determines time of corrosion initiation. The algorithm drives effective diffusivity from an apparent diffusion model, using experimental binding data performed in the lab, temperature, free ion concentration, and carbonation, and generates free chloride profiles for concrete with and without SCMs by using Fick’s law in a finite element model. Adjusting diffusion coefficient at each step of the solution, by addressing the impact of different parameters, simplifies the algorithm and reduces calculation time without jeopardizing the results’ quality. Results generated by the model compare well to the performance of concrete blocks constructed in an exposure site on the east coast of Saudi Arabia. The exposure site hosted five different mixes of Portland cement and SCMs, and the concrete blocks were exposed to harsh weather over the period of two years. Linear polarization and chloride profiling assessed the performance of the mixes against corrosion activities. Lab work identified the performance of the mixes through binding capacity and chloride profiling. Statistical analysis evidenced the accuracy of the model through correlation and regression analysis. Furthermore, a new proposed binding model, produced from binding data in different studies, alters the experimental binding data in the algorithm to decouple the solution from experimental values. The algorithm proves its accuracy when compared to the experimental free chloride profile. The proposed transport model proves that using effective diffusion and binding capacity are enough to generate reliable results, and the effective diffusion can be calibrated with environmental conditions such as temperature, age, and carbonation. Finally, the algorithm presents its features in an object-oriented programming using C# and user friendly web interface.

Mechanism and Function of the Catch State in Molluscan Smooth Muscle: A Historical Perspective.

Molluscan smooth muscles exhibit the catch state, in which both tension and resistance to stretch are maintained with very low rates of energy consumption. The catch state is studied mainly on the anterior byssus retractor muscle (ABRM) of a bivalve molluscan animal, Mytilus, which can easily be split into small bundles consisting of parallel fibers. The ABRM contracts actively with an increase in the intracellular free Ca ion concentration, [Ca2+]i, as with all other types of muscle. Meanwhile, the catch state is established after the reduction of [Ca2+]i to the resting level. Despite extensive studies, the mechanism underlying the catch state is not yet fully understood. This article briefly deals with (1) anatomical and ultrastructural aspects of the ABRM, (2) mechanical studies on the transition from the active to the catch state in the isotonic condition, (3) electron microscopic and histochemical studies on the intracellular translocation of Ca ions during the transition from the active to the catch state, and (4) biochemical studies on the catch state, with special reference to a high molecular mass protein, twitchin, which is known to occur in molluscan catch muscles.

Effects of alkali additives in saturated LiNO3 aqueous electrolyte for improvement in cycling stability of polyimide anode

In this work, the alkali additive is introduced to improve the cycling stability of polyimide anode in saturated LiNO3 aqueous electrolyte. Optimal electrolyte consists of saturated LiNO3 aqueous solution with 0.001 mol L−1 KOH, which improves the capacity retention of polyimide in a three-electrode cell. When assembling with LiCoO2 cathode, the full cells exhibit good cycling stability with high capacity retention even after 1000 cycles. The remarkable improvement in cyclic performance is attributed to the efficient suppression of hydrogen ion accumulation in the electrolyte. Furthermore, theoretical calculation results indicate that the carbonyl interactions with hydrogen ions result in poor structural stability of the polymer. The formation of colloidal LiOH is realized/obtained by introducing an appropriate amount of KOH into the saturated LiNO3 electrolyte. The resulting colloidal LiOH not only reduces the concentration of free hydroxyl ions in the electrolyte, but also continuously releases the hydroxyl ions to react with hydrogen ions. These results suggest that the introduction of alkali in saturated LiNO3 aqueous electrolytes improves the electrochemical stability of polyimide anode, which will push the practical applications of polyimide materials in aqueous Li-ion cells.

Ecotoxicity Responses of the Macrophyte Algae Nitellopsis obtusa and Freshwater Crustacean Thamnocephalus platyurus to 12 Rare Earth Elements

Due to unique chemical properties, rare earth elements (REEs) are increasingly used in versatile technological applications. They are considered emerging environmental contaminants, since they become mobile instead of being bound in rocks. At present, the information on REE effects to aquatic biota is scarce and contradictory. This study aims to explore the ecotoxicity of 11 lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, and Lu) and yttrium (Y) to charophyte algae Nitellopsis obtusa and microcrustaceans Thamnocephalus platyurus. Median lethal concentrations (LC50) were assessed in characean cells at 8, 12, 16, 20, and 24 days of exposure, and 24-h LC50s were determined in shrimps. According to the EU−Directive 93/67/EEC hazard classification scheme and 24-day LC50 values generated for N. obtusa, REE effects were assigned from “harmful” to “very toxic” (Gd), while 24-h LC50s for T. platyurus were classified as “harmful” or “toxic” (based on nominal concentrations) and as “toxic” or “very toxic” (based on REE free ion concentrations calculated with CHEAQS Next software). The data obtained for algae showed correlations with the REE atomic numbers (r = −0.68, p < 0.05) and ionic radii (r = 0.65, p < 0.05) at the most extended 24-day exposure only. The analysis of the trends of concentration−response (c–r) curves obtained at increasing exposure durations (8–24 days), alongside the 24-day LC50s ranging within almost two orders of magnitude, allowed a more-toxic heavy REE group to be distinguished, and somewhat different modes REE actions to be envisioned for N. obtusa.

Pro-Oxidant Activity of an ALS-Linked SOD1 Mutant in Zn-Deficient Form.

Cu, Zn superoxide dismutase (SOD1) is a representative antioxidant enzyme that catalyzes dismutation of reactive oxygen species in cells. However, (E,E)-SOD1 mutants in which both copper and zinc ions were deleted exhibit pro-oxidant activity, contrary to their antioxidant nature, at physiological temperatures, following denaturation and subsequent recombination of Cu2+. This oxidative property is likely related to the pathogenesis of amyotrophic lateral sclerosis (ALS); however, the mechanism by which Cu2+ re-binds to the denatured (E,E)-SOD1 has not been elucidated, since the concentration of free copper ions in cells is almost zero. In this study, we prepared the (Cu,E) form in which only a zinc ion was deleted using ALS-linked mutant H43R (His43→Arg) and found that (Cu,E)-H43R showed an increase in the pro-oxidant activity even at physiological temperature. The increase in the pro-oxidant activity of (Cu,E)-H43R was also observed in solution mimicking intracellular environment and at high temperature. These results suggest that the zinc-deficient (Cu,E) form can contribute to oxidative stress in cells, and that the formation of (E,E)-SOD1 together with the subsequent Cu2+ rebinding is not necessary for the acquisition of the pro-oxidant activity.

Geochemistry of Engineered Nanoparticles (CdSe/ZnS Quantum Dots) in Surface Waters

The difficulties when studying the behavior of engineered nanoparticles (ENPs), and the subsequent metal speciation in aquatic ecosystems, at concentrations relevant of environment (i.e. ppt level) are often related to the occurrence of ENPs constitutive elements at high concentrations as a background in aquatic media (i.e.). In this study, the physico-chemical behavior of CdSe/ZnS quantum dots (QDs) when spread at very low concentration in surface waters was investigated. The above-mentioned issues were overcome with the use of isotopically labeled QDs, separated by centrifugal ultrafiltration (CU) and measured by HR-ICP-MS, combined with the detection of free and labile metal ions by Scanned Stripping ChronoPotentiometry (SSCP). They firmly provided a thorough comprehension regarding the transformation of QDs in surface waters. The physicochemical conditions of the medium including the presence of an analogue of natural organic matter and a mineral (i.e. fulvic acid, goethite), the manufactured coating of the QDs (here thioglycolic acid), and the occurrence of added Zn in the medium, were considered in the study. The overall results show that, in the absence of mineral/organic matter, the TGA ligands in solution detached from the QDs surface after dissolution control the metal ions speciation, especially for Cd. Conversely in a more representative aquatic ecosystem conditions (i.e. with Zn in the background media together with fulvic acid and goethite), almost no Zn nor Cd dissolution from the QDs is detected. SSCP measurements reveal that the Zn complexes formed with the organic/mineral material in the system are inert, whereas the speciation model calculations indicated that Cd2+ is bound to TGA ligands in solution and organic/inorganic matter – therefore suggesting that, under the studied conditions, aquatic organisms will be exposed to a very low concentration of free and labile metal ions issued from the QDs.

Effects of ocean acidification on toxicity of two trace metals in two marine molluscs in their early life stages

Ocean acidification (OA) is usually thought to change the speciation of trace metals and increase the concentration of free metal ions, hence elevating metal bioavailability. In this study, embryos of the oysterCrassostrea angulataand abaloneHaliotis discus hannaiwere cultured under 4 pCO2conditions (400, 800, 1500 and 2000 µatm) with Cu and Zn added. Fertilization rate was measured 2 h post-fertilization (hpf), while larval deformation and larval shell length were measured 24 hpf. Our results show that OA can alleviate Cu and Zn inhibition ofC. angulatafertilization by 86.1 and 26.4% respectively, and Zn inhibition ofH. discus hannaifertilization by 43.7%. However, OA enhanced the inhibitory effect of Cu on fertilization ofH. discus hannaiby 34.7%. OA enhanced the toxic effect of Cu on larval normality ofC. angulataby 22.0% and the effect of Cu and Zn on larval normality ofH. discus hannaiby 71.4 and 37.2%, respectively. OA also enhanced the inhibitory effects of Cu and Zn on larval calcification inH. discus hannaiby 8.8 and 8.6%, respectively. However, OA did not change the effect of Cu on the calcification ofC. angulatalarvae. OA decreased Zn inhibition of oyster larval calcification from 3.1 to 1.5%. Based on our results, the toxic effects of metal on early development of molluscs are not always increased by rising pCO2and differ across developmental stages, egg structure and species. This complexity suggests that caution should be taken when carrying out multiple environmental stressor tests on molluscan embryos.

Full wave analysis of stripping chronopotentiometry at scanned deposition potential (SSCP): Obtaining binding curves in labile heterogeneous macromolecular systems for any metal-to-ligand ratio

Abstract The different deposition potentials applied in Scanned Stripping ChronoPotentiometry (SSCP) probe different values of the free metal and complex concentrations at the electrode surface. The knowledge of these concentrations gives access to a relevant window of the binding curve of a metal to a homogeneous or heterogeneous ligand. Here, a suitable mathematical treatment for the determination of these surface concentrations, when using a mercury thin film rotating disk electrode, is reported. The proposed procedure does not require ligand excess conditions and takes advantage of the knowledge of the free metal ion concentration in the bulk solution provided by the technique AGNES (Absence of Gradients and Nernstian Equilibrium Stripping). It is experimentally shown that the information derived from the SSCP points (i.e. at different deposition potentials in a unique solution) is consistent with the speciation results yielded by the technique AGNES in pertinent solutions prepared within a range of metal-to-ligand ratios. Successful examples with polystyrene sulfonate, Laurentian Fulvic acid and a peat humic acid are reported. It is concluded that, by running consecutively SSCP and AGNES in a single solution, speciation information corresponding to different compositions (i.e. those locally generated at the electrode surface by the end of the deposition step) can be retrieved, this enabling an easy determination of the binding curve.

Modification of AFLC Physical Properties by Doping with BaTiO3 Particles.

In this paper, for the first time, the influence of the BaTiO3 particles on the antiferroelectric liquid crystalline phase was shown. Low concentrations and two different sizes of BaTiO3 particles (nano- and submicroparticles) were used. It was found that admixture of the ferroelectric particles causes a decrease in the concentration of free ions in the liquid crystal matrix. Despite the small amount of admixture, a decrease in spontaneous polarization, switching time and rotational viscosity, was observed, while the tilt angle of molecules and the smectic layer thickness did not change. It turns out that BaTiO3 particles have a very large impact on the dielectric spectra not only in the antiferroelectric phase but also in the ferroelectric and paraelectric phases of the polymorphic mixture studied. The dopants affect also the complex conductivity. In this paper, we explain why some properties are modified by BaTiO3 particles and others are not.

Ratiometric imaging of flux dynamics of cobalt with an optical sensor

Cobalt (Co2+) is a vital micronutrient needed for growth and development by all life types. In humans, cobalt is cytotoxic and genotoxic associated with various pathological and physiological conditions such as allergic dermatitis, pneumonia, interstitial fibrosis, alveolitis, myocardiopathy, rhinitis and lung cancer. In this study, we present a genetically encoded fluorescence resonance energy transfer (FRET)-based Cobalt Optical Sensor (CobOS) to determine this metal ion’s trafficking scheme consisting of uptake/efflux mechanisms and measuring the real time free-ion concentration and distribution within living cells. CobOS comprise of a cobalt-sensing domain CbiKP from Desulfovibrio vulgaris Hildenborough fused with the FRET pair enhanced cyan fluorescent protein (ECFP) and Venus at N- and C-terminus respectively. When studied for its specificity and selectivity, CobOS provides maximum ratiometric readout for cobalt ions, thereby establishing its effectiveness as a FRET cobalt sensor. The sensor is resistant to pH changes and remains unaffected by adding other metal ions that are biologically significant. CobOS-86n, the most efficient sensor variant, binds cobalt with an affinity (Kd) of 0.86 × 10−6 M covering cobalt concentrations of 50 nM to 200 μM and can be of practical interest for real time measurement of in vivo cobalt levels in Escherichia coli (E. coli), yeast and mammalian cells non-invasively using widefield confocal fluorescent microscopy.