Concentration Of Phen Research Articles

Emergency of electrochemical bistability in the cathodic deposition of copper

Nanostructured metallic multilayers in the electrodeposition of copper can be spontaneously synthetized when the system is kept far from thermodynamic equilibrium. We have focused on the understanding of how blocking agents, mainly induced by strong adsorption, can tune the thickness of these self-organized layers, therefore, altering the total surface area. For this purpose, we perturbed the electrodeposition of copper on acidic media with small amounts of o-phenanthroline (phen). Indeed, the addition of phen gives rise to a distinct current-potential profile. A negative differential resistance (NDR) and hysteresis are observed in the cyclic voltammograms. The appearance of the NDR is attributed to the adsorption of some species in lower potentials, which suppresses the copper electrodeposition. The hysteresis, in its turn, indicates that the system has two stable steady states for the same set of controlling parameters, the so-called bistability (BS). We have monitored the bistability domain by mapping the bifurcation diagrams Rext (external resistance between the working and reference electrodes) vs. potential obtained from the experimental data for different concentrations of phen. We have also performed EQCN, SEM and EIS measurements in order to investigate the phenomena involved in the appearance of bistability. We have suggested a physical-chemical mechanism in attempt to explain which substances act as the surface-blocking agents.

Key role of surface concentration on reproducibility and optimization of SERS sensitivity

A systematic study was carried out demonstrating that surface concentration is the key factor that must be controlled to overcome the reproducibility problems that has long been haunting surface enhanced Raman spectroscopy (SERS), converting it in a quantitative analytic tool without using any internal standard. The 1,10‐phenanthroline molecule (phen) used as model compound can assume different orientations on the surface as a function of surface concentration, but a linear response as a function of concentration was realized in a well‐defined range of gold nanoparticles (AuNPs) and phen concentration ratios, allowing to fully explore the very high sensitivity of SERS technique. A detection at a low concentration (5.0 × 10−8 mol dm−3) was achieved controlling the surface concentration in the optimum range where the signals of the species of analytic interest are maximized whilst the signals of all other species are minimized. Copyright © 2017 John Wiley & Sons, Ltd.

The kinetics of substitution reaction of oxydiacetate and thiodiacetate copper(II) complexes with 1,10-phenanthroline and 2,2’-bipyridine

The kinetics of substitution reactions of the CuODA and CuTDA binary complexes (ODA = oxydiacetate, TDA = thiodiacetate) with 1,10-phenanthroline (phen) and 2,2’-bipyridine (bipy) were studied in aqueous and DMSO solutions. These reactions were monitored spectrometrically using the stopped-flow method in the UV range. The studies were carried out at three temperatures - 298.15, 303.15 and 308.15 K. The concentrations of the binary complexes were kept within the range of 0.2–0.5 mmol L−1, whereas the concentration of phen or bipy was constant = 0.05 mmol L−1. The values of the reaction rate constants were calculated based on the A → B reaction model. A linear relationship of the rate of the substitution reaction versus the concentration of the binary complex as well as temperature was observed. The impact of the type of the primary (ODA and TDA) and auxiliary ligands (phen and bipy) as well as the effect of solvent on the rate of substitution reaction have been discussed. The impact of the primary (ODA = oxydiacetate, TDA = thiodiacetate) and auxiliary ligands (phen and bipy) as well as the effect of solvents (DMSO and water) on the rate of substitution reaction of Cu(II) complexes have been discussed.

Crystal Structure, Antioxidant Properties and Characteristics in Aqueous Solutions of the Oxidovanadium(IV) Complex [VO(IDA)phen]·2H2O

AbstractA new oxidovanadium(IV) complex was prepared by the reaction of vanadyl acetylacetonate [VO(acac)2], iminodiacetic acid (H2IDA) and 1,10‐phenanthroline (phen) in aqueous solutions. The crystal structure of [VO(IDA)phen]·2H2O was determined by X‐ray diffraction crystallographic analysis. The stability of the title compound in aqueous solution was investigated by using potentiometric titration methods. Moreover, the kinetics of substitution reactions of the VO(IDA) binary complex with 1,10‐phenanthroline were investigated in aqueous solutions. These reactions were monitored spectrophotometrically at 249 nm by using stopped‐flow methods. Kinetic measurements were performed in the 293–308 K temperature range, at different concentrations (0.1–0.5 mM) of the binary complex and at a constant concentration of phen (0.05 mmol/L). Moreover, the antioxidant properties of this complex against superoxide radicals were studied by nitrobluetetrazolium (NBT) and cyclic voltammetry (CV) and the antioxidant properties were also investigated against two organic radicals: the 1,1‐diphenyl‐2‐picrylhydrazyl radical (DPPH·) and the 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radical (ABTS·+) by using spectrophotometric methods. The results of the antioxidant tests show that VO(IDA)phen scavenges superoxide free radicals as well as organic radicals (ABTS·+ and DPPH·).

Investigations of ternary complexes of Co(II) and Ni(II) with thiodiacetate anion and 1,10-phenanthroline or 2,2’-bipyridine in aqueous solutions

Abstract A potentiometric titration method (PT) and a stopped-flow kinetic technique monitored by a UV−Vis spectroscopy have been used to characterize the stability of series of Co(II)- and Ni(II)-thiodiacetato complexes, M(TDA), in the presence of 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) in aqueous solutions. The stability constants of the binary (1:1), ternary (1:1:1) as well as the resulting hydroxo complexes were evaluated and compared to the corresponding oxydiacetate complexes. Based on the species distribution as a function of pH the relative predominance of the species in the system over a pH range was discussed. Furthermore, the kinetic measurements of the substitution reactions of the aqua ligands to phen or bipy in the coordination sphere of the binary complexes M(TDA) were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (0.2–0.5 mM). The kinetic stability of the M(TDA) complexes was discussed in relation to the experimental conditions and the kind of the auxiliary ligands (phen/bipy). Moreover, the influence of the type of primary ligand (thiodiacetate/oxydiacetate) on the substitution rate of the auxiliary ligands was also compared.

Sol–gel derived silica thin films immobilized with 1,10-phenanthroline and their binding activity toward iron(II)

Transparent sol–gel thin films immobilized with 1,10-phenanthroline were prepared via the acid-catalyzed sol–gel reaction of tetraethylorthosilicate (TEOS) in the presence of phen. Three surfactants that include cationic cetyl trimethyl ammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS) and non-ionic Triton X-100 (TX-100) were tested for the improvement of the host material mesostructure, increasing its porosity and good accommodation of the phen within the silica matrix. The immobilized phen thin films showed similar behavior as their free counterpart in aqueous solution. The immobilized phen complex retained its activity toward Fe2+ metal ions by immobilization and produced a stable complex without any shift in the wavelength of Vis absorption spectra comparing with its free counterpart. Different parameters including concentrations of phen, Fe2+ and surfactant, type of surfactant, lifetime and number of measurements were investigated. The phen thin film sensor showed high sensitivity, chemical stability, good reproducibility and long lifetime behavior. The immobilized phen thin films were used for quantification of iron(II) in versatile aqueous samples. The polarized light microscopy indicated that the phen molecules were distributed uniformly within the host silica network.

Investigations of ternary complexes of Co(II) and Ni(II) with oxydiacetate anion and 1,10-phenanthroline or 2,2′-bipyridine in solutions

AbstractPotentiometric (PT) and conductometric (CT) titration methods have been used to determine the stoichiometry and formation constants in water for a series of ternary complexes of Co(II) and Ni(II) involving the oxydiacetate anion (ODA) and 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) ligands, namely [Co(ODA)(phen)(H2O)], [Co(ODA)(bpy)(H2O)], [Ni(ODA)(phen)(H2O)] and [Ni(ODA)(bpy)(H2O)]. The ternary complex formation process was found to take place in a stepwise manner in which the oxydiacetate ligand acts as a primary ligand and the phen or bipy ligands act as auxiliary ones. The stability of the ternary complexes formed is discussed in the relation to the corresponding binary ones. Furthermore, the kinetics of the substitution reactions of the aqua ligands in the coordination sphere of the Ni-ODA and Co-ODA complexes to phen or bipy were studied by the stopped-flow method. The kinetic measurements were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (4–7 mM). The influence of experimental conditions and the kind of the auxiliary ligands (phen/bipy) on the substitution rate was discussed.

Surface-Enhanced Raman Scattering Determination of Trace Phenanthroline Using Aggregated-Nanosilver as Substrate

Using PEG10000 and sodium citrate as stabilizer, sodium borohydride as reducing agent, a stable nanosilver sol had been prepared. In pH 6.0 Na2HPO4- NaH2PO4buffer solution and in the presence of NaCl, a stable nanosilver aggregates were formed. Phenanthroline (Phen) adsorbed on the aggregated-nanosilver surfaces resulting in a surface-enhanced Raman scattering (SERS) peak at 1450 cm-1observed, and the SERS intensity was enhanced with the concentration of Phen was between 1.25×10-10mol/L and 2.5×10-9mol/L. Based on these, a new sensitive SERS method has been proposed for the determination of trace Phen in the synthesis of samples, with satisfactory results.

Role of extractable and residual organic matter fractions on sorption of phenanthrene in sediments

Two sediments were demineralized and sequentially fractionated into extracted fractions [free lipid (FL), bound lipid (BL) and lignin (LG)] and residual fractions [free lipid free (FLF), bound lipid free (BLF) and lignin free (LGF)]. The sorption isotherms of phenanthrene (Phen) were examined to evaluate the importance of various fractions on sorption. A lignin extraction procedure was for the first time applied to separate the lignin or degraded lignin fraction from sediment organic matter (SOM). The extracted LG was similar to model lignin in terms of elemental ratios and sorption behavior. FL and LG fractions were quite important, as their contents were much higher than reported values. Phen sorption for the extracted fractions was almost linear, whereas that for the residual fractions was nonlinear, especially for LGF with n 0.56–0.63. As the different organic fractions were removed sequentially, sorption energy distribution on the residual sediment organic matter (SOM) became more heterogeneous. In addition, increasing sorption capacity for the residual fractions, except for BLF with its high polarity, suggested that more sorption sites on the SOM matrix became accessible to Phen. The sorption capacity for LGF was comparable to that of condensed SOM. The residual fraction LGF generally controlled the overall sorption at low Phen concentration, but the extractable fraction FL surpassed the former fraction at high Phen concentration, demonstrating the importance of condensed SOM in the sorption of hydrophobic organic compounds (HOCs) in sediments.

Determination of lead(II) by online novel electrolyte dropping electrode using 1,10-phenanthroline in flow injection system

The transfer of Pb(II) facilitated by 1,10-phenanthroline (phen) presented in the methyl isobutyl ketone (MIBK) across the polarized water|MIBK interface was systematically investigated by novel electrolyte dropping electrode using cyclic voltammetry and square wave voltammetry. The protonation of 1,10-phenanthroline in polarized water|MIBK interface was explored. The dependence of the half-wave potential on PbCl2 and phen concentration was investigated and the stoichiometry of resulting metal ligand complex was formulated. Different concentrations of PbCl2 was determined online and the transfer peak current was proportional to the bulk concentration of the Pb2+ varied between 8 μM to 0.5 mM and 0.5 to 1 mM, and the linear regression coefficients were 0.9953 and 0.9995, respectively. The standard deviations (RSD) were 4.33, 5.80, 4.13, 3.88, 2.23, 3.39, 1.38, 2.42, 2.00, 2.73 and 2.37% for 8 times successive determinations of Pb2+ for the concentrations of 0.008, 0.05, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, 0.8, 0.9 and 1 mM, respectively. The long time stability of the electrolyte dropping electrode was tested and the result showed that this novel method was simple, rapid and efficient.

Study of Enhanced Chemiluminescence of Diperiodatocuprate (III) on 1,10-Phenanthroline/Hydrogen Peroxide/Cetyltrimethylammonium Bromide System

In the paper, a chemiluminescence (CL) system was developed based on the catalytical effect of diperiodatocuprate (III) (DPC) on the 1,10-phenanthroline (phen)/hydrogen peroxide (H(2)O(2)) in the presence of cetyltrimethylammonium bromide (CTAB). The effects of experimental conditions were investigated. Meanwhile the increase of CL intensity of the DPC/phen/H(2)O(2)/CTAB system is proportional to the concentration of phen in the range of low concentration. The linear range of the calibration curve is 5.0 × 10(-9)-1.0 × 10(-6) mol L(-1), and the corresponding detection limit is 1.9 × 10(-9) mol L(-1). The effects of phenolic compounds (PCs) on the system were investigated. Hydroquinone was used as an example to investigate the application of the CL system to the determination of PCs. The quenched CL intensity is linearly related to the logarithm of concentration of hydroquinone. The linear range of the calibration curve is 2.5 × 10(-9)-1.0 × 10(-5) g mL(-1), and the corresponding detection limit is 1.8 × 10(-9) g mL(-1). This phen and hydroquinone can be synchronously determined. The method was applied to the determination of hydroquinone in water samples and the recoveries were from 92% to 106%.

Structural, Thermal, and Fluorescence Properties of Eu(DBM)3Phenx Complex Doped in PMMA

Tris (dibenzoylmethanido) (o-phenanthroline)-europium(III) complexes [Eu(DBM)(3)(Phen)(x)] have been synthesized, and their structural, thermal, and fluorescence properties have been investigated both as an independent complex and also after embedding it in poly(methyl methacrylate) (PMMA) polymer matrix. X-ray analysis reveals an unusual crystalline to amorphous transformation in structure of the Eu(DBM)(3)Phen(x) complexes when x exceeds 1.0 (mole %). Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) analysis depict the interaction between the Eu(DBM)(3)Phen(x) complex and the PMMA matrix. The fluorescence intensity of Eu(3+) ion in the Eu(DBM)(3)Phen(1·5) complex is an order of magnitude larger compared to the Eu(DBM)(3)·2H(2)O complex. In addition to the transition (5)D(0) → (7)F(2,) which has a rise time of 83 μs, transitions from the (5)D(1) and (5)D(2) levels are also observed, along with several ligand field splittings in the Eu(DBM)(3)Phen(1·5) complex. Appearance of a rise time (∼0.76 ns) in the decay of the fluorescence from DBM in the presence of Phen and a simultaneous large decrease in the fluorescence intensity (both the singlet and triplet emission) of DBM along with a decrease in fluorescence decay time, in the presence of Eu(3+), indicates a cascading excitation energy transfer from Phen to DBM and finally to the (5)D(0) state of Eu(3+) ion in Eu(DBM)(3)Phen(1.5) through short-range excitation energy transfer. A systematic and significant improvement in the thermal and fluorescence properties of the complex is observed with an increase in the mole concentration of Phen. The maximum fluorescence is observed for Eu(DBM)(3)Phen(1·5), which is a new composition as compared with the usual composition reported earlier. This finding indicates the possibility for the development of brighter luminescent lanthanide photonic materials.

Characteristics of earthworms ( Eisenia fetida) in PAHs contaminated soil amended with sewage sludge or vermicompost

Earthworms can be used to remove polycyclic aromatic hydrocarbons (PAHs) from soil, but this might affect their survival and they might accumulate the contaminants. Sterilized and unsterilized soil was contaminated with phenanthrene (Phen), anthracene (Anth) and benzo(a)pyrene (BaP), added with or without Eisenia fetida, sewage sludge or vermicompost. Survival, growth, cocoon formation and concentrations of PAHs in the earthworms were monitored for 70 days. Addition of sewage sludge to sterilized or unsterilized soil maintained the number of earthworms and their survival was 94%. The addition of sludge significantly increased the weight of earthworms 1.3 times compared to those kept in the unamended soil or in soil amended with vermicompost. The weight of earthworms was significantly lower in sterilized than in unsterilized soil. Cocoons were only detected when sewage sludge was added to unsterilized soil. A maximum concentration of 62.3 μg Phen kg −1 was found in the earthworms kept in sterilized soil amended with vermicompost after 7 days and 22.3 μg Phen kg −1 when kept in the unamended unsterilized soil after 14 days. Concentrations of Phen in the earthworms decreased thereafter and ≤2 μg kg −1 after 28 days. A maximum Anth concentration of 82.5 μg kg −1 was found in the earthworms kept in sterilized soil amended with vermicompost and 45.8 μg Anth kg −1 when kept in the unamended unsterilized soil after 14 days. A maximum concentration of 316 μg BaP kg −1 was found in the earthworms kept in sterilized soil amended with vermicompost after 56 days and 311 μg BaP kg −1 when kept in the unsterilized soil amended with vermicompost after 28 days. The amount of BaP in the earthworm was generally largest after 28 days, but after 70 days still 60 μg kg −1 was found in E. fetida when kept in the sterilized soil amended with sewage sludge. It was found that E. fetida survived in PAHs contaminated soil and accumulated only small amounts of the contaminants, but sewage sludge was required as food for its survival and cocoon production.

Energy transfer from Eu(III) complexes to dyes in their mixed nanostructures. II

The effects of the concentration of a number of dyes in an aqueous solution and of the method of formation of mixed nanostructures of dyes and Eu(MBTA)3phen (MBTA is p-methoxybenzoyltrifluoroacetone; phen is 1,10-phenanthroline) complexes that form these structures on the luminescence decay kinetics of Eu(III) ions are studied. It is shown that, in the concentration range 5–50 nM of Nile blue, the concentration dependences of the luminescence decay and of the decrease in τlum of Eu(III) nearly coincide and are nearly linear. The dependence of the ratio of Ilum of Eu(III) to the intensity of the sensitized delayed fluorescence of Nile blue on the delay time of the probe pulse is analyzed; it is found that the majority of dye molecules incorporated in nanostructures of Eu(MBTA)3phen complexes emit sensitized delayed fluorescence with times 1–50 μs. Analysis of the effect of the structure of nanostructures on the quenching of Ilum of Eu(III) by the dye at different concentrations of Eu(III) shows that nanostructures of Eu(MBTA)3phen and Eu(NTA)3phen (NTA is 2-naphthoyltrifluoroacetone) complexes appear in the aqueous solution at a concentration of Eu(III) of 0.1 μM (the MBTA or NTA concentration is 50 μM, and the concentration of phen is 17 μM) and exist in the solution at the Eu(III) concentrations up to ∼5 μM. This confirms the conclusion on the occurrence range of nanostructures of Ln complexes previously made based on the analysis of columinescence in these structures.

Strong Sorption of Phenanthrene by Condensed Organic Matter in Soils and Sediments

The nonhydrolyzable carbon (NHC) and black carbon (BC) in three contaminated soils and seven sediments from the Pearl River Delta and Estuary, China, were isolated upon treatments with an acid hydrolysis method and with a combustion method at 375 degrees C, respectively, and their sorption isotherms for phenanthrene (Phen) were established. It was found that NHC is chemically and structurally different from the biopolymer and humic substances and consists mainly of aliphatic and aromatic carbon using elemental analysis, 13C nuclear magnetic resonance spectroscopy (13C NMR), and Fourier transformed infrared spectroscopy (FTIR). All the sorption isotherms are nonlinear and are well fitted by the Freundlich model. The single-point organic carbon-normalized distribution coefficient (K(oc)) measured for the isolated NHC is 1.3-7.7 times higher than that for the bulk samples at the same aqueous concentration of Phen. The NHC fractions play a dominant role to the overall sorption in the bulk samples. The bulk soils and their NHC fractions have lower sorption capacity than the bulk sediments and their NHC fractions, relating to the different source of organic matter between soils and sediments. The Phen sorption capacity in the NHC samples is related significantlyto H/C ratios and aliphatic carbon, but negatively to aromatic carbon, demonstrating the important role of aliphatic carbon to the Phen sorption and the fate in the investigated soils and sediments.

Joint Toxicity of Cadmium and Phenanthrene in the Freshwater Amphipod Hyalella azteca

The joint toxicity of combined metals and polynuclear aromatic hydrocarbons is poorly understood and may deviate from the summed concentration responses of the individual pollutants. The freshwater amphipod Hyalella azteca was exposed to sediment-amended Cd and phenanthrene (Phen) individually and in combination using United States Environmental Protection Agency 10-day sediment toxicity bioassays with lethality and growth end points. The lethal joint toxicity of Cd and Phen was investigated separately in 24-, 48-, and 72-hour aqueous exposures. In sediment exposures, a sublethal concentration of Phen (144 mg kg(-1)) in combination with Cd increased mortality across a range of Cd concentrations and decreased the 10-day LC50 for Cd from 523 mg kg(-1) (461 to 588, 95% confidence interval [CI]) to 263 mg kg(-1) (214 to 312, 95% CI). In contrast, sublethal concentrations of Phen had no effect on the lethal toxicity of Cd in aqueous exposures. Combined sediment-amended Cd and Phen acted independently on growth rate. Rate decreases were driven primarily by Cd. Our findings indicated that association with sediment influences the joint toxicity of Cd and Phen. Thus, mixtures of Cd and Phen may cause synergistic or independent toxicity in H. azteca depending on the end point investigated and the experimental protocol employed. As an implication of these results, the interpretation of standardized toxicity bioassays, including whole-effluent toxicity tests and single-compound toxicity tests, must be made with caution. These assessment protocols may underestimate potentially hazardous mixture effects in sediment environments. Therefore, risk assessment protocols for environments containing metal-PAH mixtures must include robust methods that can detect possible interactive effects among contaminants to optimize environmental protection.

Sorption Kinetics of Organic Contaminants by Sandy Aquifer and Its Kerogen Isolate

Long-term sorption behaviors of phenanthrene (Phen) on the Borden sand from 1 min to 365 days and of Phen and 1,2-dichlorobenzene (DCB) on the isolated kerogen from 1 to 120 days were characterized by examining the time dependence of solute phase distribution relationships (PDRs) and compared with the prior reported sorption of tetrachlorobenzene (TeCB) and tetrachloroethene (PCE) on the pulverized and/or acid-treated bulk sand and size fractions. The sorption kinetics for Phen on the bulk sand and its kerogen isolate can well be described by the fractional power kinetics equation (q(e) = kt(b)). The similar rate parameter b for q(e)(t) vs t at 5-7 levels of initial concentrations of Phen on the two sorbents, respectively, ranging from 0.077 to 0.099 and from 0.072 to 0.086, indicates the similar sorption kinetics rate. The modified-Freundlich parameters of TeCB on the pulverized or acid-treated 0.3-mm size fraction match those of Phen on the isolated kerogen, suggesting the same natural organic matter (NOM) property of the two sorbents. As the prior investigation underestimated the Koc value for the TeCB sorption on the acid-treated 0.3-mm size fraction by a factor of 1.76, the estimated time to reach 95% of sorption equilibrium is much longer than the prior estimation (over 10 years vs about 2.5 years). The estimated times to reach 95% of sorption equilibrium at three levels of relative solubility for Phen on the bulk sand and its isolated kerogen are, respectively, longer than one decade, demonstrating the similar diffusion length for Phen on the two sorbents. The observed slow sorption kinetics is related to nanometer-pore diffusion within kerogen matrix. The investigation supplies new clues for explaining the often observed much longer persistence of organic contaminants in soils and sediments than the prediction based on the short-term laboratory experiment.

Studies in the Biodegradation of 5 PAHs (Phenanthrene, Pyrene, Fluoranthene, Chrysene und Benzo(a)pyrene) in the Presence of Rooted Poplar Cuttings

Cuttings of Populus nigra L. cv. Loenen were cultivated in sand treated with one of the following PAHs: phenanthrene (Phen), fluoranthene (Flt), pyrene (Pyr), chrysene (Chr) and benzo[a]pyrene (BaP). The PAHs were applied at varying levels of concentration to each test series. After 6 weeks the concentration and the distribution of the PAHs in the substrate of the various sets of tests were compared with the concentration in the substrate of the control. Additionally the substrate and the plant roots were tested for evidence of degradation products of PAHs. The results revealed that the levels of concentration of Phen and Pyr detected in the substrate surrounding the roots was in some cases significantly lower than in the corresponding section of substrate in the unplanted set (= control). This phenomenon did not occur for Flt and BaP and in the case of Chr only in those substrates, which had been treated with the highest levels of concentration. As the presence of lesser amounts of Phen and Pyr in the plant pots cannot only be attributed to their accumulation and metabolism in the roots, it is fair to assume that the chemical transformation of these three PAHs took place outside the roots. The set of tests treated with Phen revealed the presence of 2- or 3-hydroxy-Phen (main components), a hydroxy-methoxy-Phen, 9,10-Phenanthrenequinone and one unidentified compound in metabolite form. Altogether eleven metabolites of Pyr were identified in the root extracts, which can be divided into three groups: 1-Hydroxy-Pyr and derivatives, dihydroxy-Pyr and derivatives and ring fission products (4-Hydroxy-Pyr and a derivative of the 4-Phen-carbonic acid). However, the metabolite mass detected for Phen and Pyr represents only an insignificant percentage in comparison with the lesser amounts of PAHs observed in the planted set of tests. This indicates that the three PAHs were reduced to lower molecular compounds, which are methodically impossible to record, and subsequently translocated to other parts of the plant and integrated into the biomass. Although no lesser amount for Flt and BaP was found in the plant pots, 1-Hydroxy-Flt, an unidentified compound of Flt and 1-Methoxy-BaP were detected. These are presumably end products which were enhanced in the roots. It was not possible to identify any transformation products of Chr. It can be assumed that the majority of metabolites were not synthesised in the roots but are a result of microbial degradation in the rhizosphere. The test plants improved the conditions for the biotransformation of Phen and Pyr significantly and accumulated Flt, Pyr, Chr and BaP in their roots. It can therefore be concluded that the use of plants in the bioremediation of contaminated soils is a promising option.

Mechanism of neuromuscular blockade induced by phenthonium, a quaternary derivative of (-)-hyoscyamine, in skeletal muscles.

1. The mechanisms underlying the postjunctional blockade induced by phenthonium [N-(4-phenyl) phenacyl 1-hyoscyamine] were investigated in mammalian and amphibian muscles. This muscarinic antagonist was previously shown to enhance specifically the spontaneous acetylcholine (ACh) release at concentrations that blocked neuromuscular transmission. 2. In both rat diaphragm and frog sartorius muscles, phenthonium (Phen, 1-100 microM) depressed the muscle twitches elicited by nerve stimulation (IC50: 23 microM and 5 microM, respectively), and blocked the nerve-evoked muscle action potential. The neuromuscular blockade was not reversed after incubation with neostigmine. 3. Equal concentrations of Phen decreased the rate of rise and prolonged the falling phase of the directly elicited action potential in frog sartorius muscle fibres, indicating that the drug also affects the sodium and potassium conductance. 4. Phen (50 and 100 microM) protected the ACh receptor against alpha-bungarotoxin (BUTX) blockade in the mouse diaphragm allowing recording of endplate potentials and action potentials after 5 h wash with physiological salt solution. 5. Phen (10-100 microM) produced a concentration- and voltage-dependent decrease of the endplate current (e.p.c.), and induced nonlinearity of the current-voltage relationship. At high concentrations Phen also shortened the decay time constant of e.p.c (tau(e.p.c.)) and reduced its voltage sensitivity. 6. At the same range of concentrations, Phen also reduced the initial rate of [125I]-BUTX binding to junctional ACh receptors of the rat diaphragm (apparent dissociation constant = 24 microM), the relationship between the degree of inhibition and antagonist concentration being that expected for a competitive mechanism. 7. It is concluded that Phen affects the electrical excitability of the muscle fibre membrane, and blocks neuromuscular transmission through a mechanism that affects the agonist binding to its recognition site and ionic channel conductance of the nicotinic ACh receptor.

Voltammetric study of protonated 1,10-phenanthroline cation transfer across the water/nitrobenzene interface

The ion transfer of 1,10-phenanthroline (phen) across the water/nitrobenzene interface has been studied in the pH range 1–7 by electrochemical methods, adding phen to the aqueous phase or to the organic (nitrobenzene) phase. Current-scan polarography at an ascending water electrode and potential-scan cyclic voltammetry at a stationary plane electrode were used. With each addition, an anodic wave caused by the transfer of a protonated phen (Hphen +) from the aqueous to the organic phase was observed. Here a detailed mechanism of the ion transfer is proposed by considering branch diffusions of phen species from the interface to either bulk phase by which the Hphen + transfer producing the anodic wave is depressed. With the addition of phen to the aqueous phase, the wave became deformed, noisy and steep, and finally separated into two waves as the phen concentration was increased and the pH was decreased. This is probably caused by the interfacial adsorption of Hphen +. The adsorption phenomenon is also discussed with the aid of electrocapillary curves.