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G L (g + l)
Selected AbstractsDevelopment and evaluation of efficient recombinant Escherichia coli strains for the production of 3-hydroxypropionic acid from glycerol,BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2009Chelladurai Rathnasingh Abstract 3-Hydroxypropionic acid (3-HP) is a commercially valuable chemical with the potential to be a key building block for deriving many industrially important chemicals. However, its biological production has not been well documented. Our previous study demonstrated the feasibility of producing 3-HP from glycerol using the recombinant Escherichia coli SH254 expressing glycerol dehydratase (DhaB) and aldehyde dehydrogenase (AldH), and reported that an "imbalance between the two enzymes" and the "instability of the first enzyme DhaB" were the major factors limiting 3-HP production. In this study, the efficiency of the recombinant strain(s) was improved by expressing DhaB and AldH in two compatible isopropyl-thio-,-galactoside (IPTG) inducible plasmids along with glycerol dehydratase reactivase (GDR). The expression levels of the two proteins were measured. It was found that the changes in protein expression were associated with their enzymatic activity and balance. While cloning an alternate aldehyde dehydrogenase (ALDH), ,-ketoglutaric semialdehyde dehydrogenase (KGSADH), instead of AldH, the recombinant E. coli SH-BGK1 showed the highest level of 3-HP production (2.8,g/L) under shake-flask conditions. When an aerobic fed-batch process was carried out under bioreactor conditions at pH 7.0, the recombinant SH-BGK1 produced 38.7,g 3-HP/L with an average yield of 35%. This article reports the highest level of 3-HP production from glycerol thus far. Biotechnol. Bioeng. 2009; 104: 729,739 © 2009 Wiley Periodicals, Inc. [source] Plasmid system for the intracellular production and purification of affinity-tagged proteins in Bacillus megaterium,BIOTECHNOLOGY & BIOENGINEERING, Issue 3 2007Rebekka Biedendieck Abstract A multiple vector system for the intracellular high-level production of affinity tagged recombinant proteins in Bacillus megaterium was developed. The N- and C-terminal fusion of a protein of interest to a Strep II and a His6 -tag is possible. Corresponding genes are expressed under the control of a xylose-inducible promoter in a xylose isomerase deficient host strain. The exemplatory protein production of green fluorescent protein (GFP) showed differences in produced and recovered protein amounts in dependence of the employed affinity tag and its N- or C-terminal location. Up to 9 mg GFP per liter shake flask culture were purified using one-step affinity chromatography. Integration of a protease cleavage site into the recombinant fusion protein allowed tag removal via tobacco etch virus (TEV) protease or Factor Xa treatment and a second affinity chromatographic step. Up to 274 mg/L culture were produced at 52 g CDW/L using a glucose limited fedbatch cultivation. GFP production and viability of the production host were followed by flow cytometry. Biotechnol. Bioeng. 2007;96: 525,537. © 2006 Wiley Periodicals, Inc. [source] Effect of the applied organic load rate on biodegradable polymer production by mixed microbial cultures in a sequencing batch reactorBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2006Davide Dionisi Abstract This article studies the operation of a new process for the production of biopolymers (polyhydroxyalkanoates, PHAs) at different applied organic load rates (OLRs). The process is based on the aerobic enrichment of activated sludge to obtain mixed cultures able to store PHAs at high rates and yields. A mixture of acetic, lactic, and propionic acids at different concentrations (in the range 8.5,31.25 gCOD/L) was fed every 2 h in a sequencing batch reactor (SBR). The resulting applied OLR was in the range 8.5,31.25 gCOD/L/day. Even though, as expected, the increase in the OLR caused an increase in biomass concentration (up to about 8.7 g COD/L), it also caused a relevant decrease of maximal polymer production rate. This decrease in polymer production rate was related to the different extent of "feast and famine" conditions, as function of the applied OLR and of the start-up conditions. As a consequence the best performance of the process was obtained at an intermediate OLR (20 gCOD/L/day) where both biomass productivity and PHA storage were high enough. However, at this high OLR the process was unstable and sudden decrease of performance was also observed. The sludge characterized by the highest PHA storage response was investigated by 16S rDNA clone library. The clone library contained sequences mostly from PHA producers (e.g., Alcaligenes and Comamonas genera); however many genera and among them, one of the dominant (Thauera), were never described before in relation to PHA storage response. © 2005 Wiley Periodicals, Inc. [source] Development and field validation of a predictive copper toxicity model for the green alga Pseudokirchneriella subcapitataENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2003Karel A. C. De Schamphelaere Abstract In this sudy, the combined effects of pH, water hardness, and dissolved organic carbon(DO) concentration and type on the chronic (72-h) effect of copper on growth inhibition of the green alga Pseudokirchneriella subcapitata were investigated. Natural dissolved organic matter (DOM) was collected at three sites in Belgium and The Netherlands using reverse osmosis. A full central composite test design was used for one DOM and a subset of the full design for the two other DOMs. For a total number of 35 toxicity tests performed, 72-h effect concentration resulting in 10% growth inhibition (EbC10s) ranged from 14.2 to 175.9 ,g Cu/L (factor 12) and 72-h EbC50s from 26.9 to 506.8 ,g Cu/L (factor 20). Statistical analysis demonstrated that DOC concentration, DOM type, and pH had a significant effect on copper toxicity; hardness did not affect toxicity at the levels tested. In general, an increase in pH resulted in increased toxicity, whereas an increase of the DOC concentration resulted in decreased copper toxicity. When expressed as dissolved copper, significant differences of toxicity reduction capacity were noted across the three DOM types tested (up to factor 2.5). When expressed as Cu2+ activity, effect levels were only significantly affected by pH; linear relationships were observed between pH and the logarithm of the effect concentrations expressed as free copper ion activity, that is, log(EbC50) and log(EbC10): (1) log(EbC50) = ,1.431 pH + 2.050 (r2 = 0.95), and (2) log(EbC10) = ,1.140 pH , 0.812 (r2 = 0.91). A copper toxicity model was developed by linking these equations to the WHAM V geochemical speciation model. This model predicted 97% of the EbC50dissolved and EbC10dissolved values within a factor of two of the observed values. Further validation using toxicity test results that were obtained previously with copper-spiked European surface waters demonstrated that for 81% of tested waters, effect concentrations were predicted within a factor of two of the observed. The developed model is considered to be an important step forward in accounting for copper bioavailability in natural systems. [source] Time-Dependent transcriptional profiles of genes of the hypothalamic-pituitary-gonadal axis in medaka (Oryzias latipes) exposed to fadrozole and 17,-trenboloneENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2008Xiaowei Zhang Abstract Both the anabolic androgen 17,-trenbolone (TRB) and the aromatase inhibitor fadrozole (FAD) can cause decreased plasma concentrations of estrogen (E2) and reduce fecundity of fish. However, the underlying mechanisms and the molecular pathways involved are largely unknown. The present study was designed to assess time-dependent effects of FAD and TRB on the transcriptional responses of the hypothalamic-pituitary-gonadal (HPG) axis of Japanese medaka (Oryzias latipes). Fourteen-week-old Japanese medaka were exposed to 50 ,g FAD/L or 2 ,g TRB/L in a 7-d static renewal test, and the expression profiles of 36 HPG axis genes were measured by means of a medaka HPG real-time reverse-transcription polymerase chain reaction array after 8 h, 32 h, or 7 d of exposure. Exposure to TRB or FAD caused lesser fecundity of Japanese medaka and down-regulated transcription of vitellogenin and choriogenin (CHG) gene expression in the liver of females. Exposure to FAD for 8 h resulted in an 8-fold and 71-fold down-regulation of expression of estrogen receptor , and choriogenin L (CHG L), respectively, in female liver. 17,-Trenbolone caused similar down-regulation of these genes, but the effects were not observed until 32 h of exposure. These results support the hypothesis that FAD reduces plasma E2 more quickly by inhibiting aromatase enzyme activity than does TRB, which inhibits the production of the E2 precursor testosterone. Exposure to FAD and TRB resulted in rapid (after 8 h) down-regulation of luteinizing hormone receptor and low-density-lipoprotein receptor in the testis to compensate for excessive androgen levels. Overall, the molecular responses observed in the present study differentiate the mechanisms of the reduced fecundity by TRB and FAD. [source] Uptake and biotransformation of 2,4,6-trinitrotoluene (TNT) by microplantlet suspension culture of the marine red macroalga Portieria hornemanniiBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2006Octavio Cruz-Uribe Abstract Microplantlets of the marine red macroalga Portieria hornemannii efficiently removed the explosive compound 2,4,6-trinitrotoluene (TNT) from seawater. Photosynthetic, axenic microplantlets (1.2 g FW/L) were challenged with enriched seawater medium containing dissolved TNT at concentrations of 1.0, 10, and 50 mg/L. At 22°C and initial TNT concentrations of 10 mg/L or less, TNT removal from seawater was 100% within 72 h, and the first-order rate constant for TNT removal ranged from 0.025 to 0.037 L/gFW h under both illuminated conditions (153 µE/m2s, 14:10 LD photoperiod) and dark conditions. Two immediate products of TNT biotransformation, 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dintrotoluene, were identified in the liquid culture medium, with a maximum material balance recovery of 29 mole%. Only trace levels of these products and residual TNT were found within the fresh cell biomass. Removal of TNT by P. hornemannii microplantlets at initial concentrations of 1.0 or 10 mg/L did not affect the respiration rate. At an initial TNT concentration of 10 mg/L, net photosynthesis decreased towards zero, commensurate with the removal of dissolved TNT from seawater, whereas at an initial TNT concentration of 1.0 mg/L, the net photosynthesis rate was not affected. © 2005 Wiley Periodicals, Inc. [source] Impact of the extent and duration of cytoreductive surgery on postoperative hematological toxicity after intraperitoneal chemohyperthermia for peritoneal carcinomatosisJOURNAL OF SURGICAL ONCOLOGY, Issue 4 2005Dominique Elias MD Abstract Background Peritoneal carcinomatosis (PC) is a major disease, currently treated using complete cytoreductive surgery and intraperitoneal chemohyperthermia (IPCH). Morbidity is a significant limitation of this procedure, usually related to the extent of surgery, and hematological toxicity, which is considered as dependent upon the chemotherapy dosage alone. The aim of our study was to investigate whether surgery alone had an impact on the hematological toxicity associated with the standardized drug protocol that we routinely prescribed. Methods Data were prospectively recorded from 83 consecutive patients who underwent complete cytoreductive surgery followed by IPCH with intraperitoneal oxaliplatin (360 mg/m2) and irinotecan (360 mg/m2), in 2 L/m2 of dextrose over 30 min at 42,45°C, using the Coliseum technique. Sixty minutes prior to IPCH, patients also received an intravenous perfusion of leucovorin (20 mg/m2) and 5-fluorouravyl (400 mg/m2). The doses and volume of IPCH were determined on the basis of the body surface area, so that all patients received the same concentration of drugs. Severe aplasia were defined as a leucocyte count of <500/ml, platelets <50,000/ml, and reticulocytes <6.5 g Hb/L. Results Postoperatively, severe aplasia was seen in 40 of the 83 patients (48%). There was no difference in the characteristics of patients with and without aplasia, other than the extent of surgery. The incidence of severe aplasia was only related to the duration of surgery (537 min in the aplastic group versus 444 min in the non aplastic group) (P,=,0.002), and to the extent of the peritoneal disease (peritoneal index of 19.5 in the aplastic group, vs. 15.3 in the nonaplastic group) (P,=,0.02). Conclusion We report for the first time that the duration of surgery may increase the incidence of hematological toxicity following intraperitoneal chemotherapy. We also hypothesized that intra- and postoperative transient biochemical disorders, such as hypoalbuminemia, hemodilution, liver, and renal insufficiency and stress can be involved in this process. These hypotheses may allow improved postoperative care. J. Surg. Oncol. 2005;90:220,225. © 2005 Wiley-Liss, Inc. [source] Acute and chronic toxicity of mercury to early life stages of the rainbow mussel, Villosa iris (Bivalvia: Unionidae)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Theodore W. Valenti Abstract Mercury (Hg) contamination is receiving increased attention globally because of human health and environmental concerns. Few laboratory studies have examined the toxicity of Hg on early life stages of freshwater mussels, despite evidence that glochidia and juvenile life stages are more sensitive to contaminants than adults. Three bioassays (72-h acute glochidia, 96-h acute juvenile, and 21-d chronic juvenile toxicity tests) were conducted by exposing Villosa iris to mercuric chloride salt (HgCl2). Glochidia were more sensitive to acute exposure than were juvenile mussels, as 24-, 48-, and 72-h median lethal concentration values (LC50) for glochidia were >107, 39, and 14 ,g Hg/L, respectively. The 24-, 48-, 72-, and 96-h values for juveniles were 162, 135, 114, and 99 ,g Hg/L, respectively. In the chronic test, juveniles exposed to Hg treatments ,8 ,g/L grew significantly less than did control organisms. The substantial difference in juvenile test endpoints emphasizes the importance of assessing chronic exposure and sublethal effects. Overall, our study supports the use of glochidia as a surrogate life stage for juveniles in acute toxicity tests. However, as glochidia may be used only in short-term tests, it is imperative that an integrated approach be taken when assessing risk to freshwater mussels, as their unique life history is atypical of standard test organisms. Therefore, we strongly advocate the use of both glochidia and juvenile life stages for risk assessment. [source] A New Type of Bismuth Electrode for Electrochemical Stripping Analysis Based on the Ammonium Tetrafluorobismuthate Bulk-Modified Carbon PasteELECTROANALYSIS, Issue 13 2010Hanna Sopha Abstract A carbon paste electrode bulk-modified with ammonium tetrafluorobismuthate (BiF4 -CPE) was developed and examined in the anodic stripping voltammetric mode for measurement of selected trace heavy metals. The BiF4 -CPE has revealed a favorable performance in more acidic solutions (pH,0.5,2.5) in the presence of dissolved oxygen for Cd(II) and Pb(II) as model metal ions at the low ,g L,1 concentration level. In comparison with the bismuth-oxide bulk-modified carbon paste electrode and the other two bismuth film-plated carbonaceous substrate electrodes examined, the BiF4 -CPE proved to be another attractive variant of the environmentally friendly bismuth-based electrodes, particularly convenient for analysis of acidified water samples. [source] Simultaneous Determination of Trace Zinc(II) and Cadmium(II) by Differential Pulse Anodic Stripping Voltammetry Using a MWCNTs,NaDBS Modified Stannum Film ElectrodeELECTROANALYSIS, Issue 23 2009Qing Tian Abstract A multiwalled carbon nanotubes,sodium dodecyl benzene sulfonate (MWCNTs,NaDBS) modified stannum film electrode was employed for the determination of cadmium(II) and zinc(II). The Sn/MWCNTs-NaDBS film electrode was prepared by applying MWCNTs,NaDBS suspension to the surface of the GCE, while the Sn film was plated in situ simultaneously with the target metal ions. Under optimal conditions, linear calibration curves were obtained in a range of 5.0 ,100.0,,g L,1 with detection limits of 0.9,,g L,1 for zinc(II) and 0.8,,g L,1 for cadmium(II), respectively. This film electrode was successfully applied to the determination of Zn(II) and Cd(II) in tap water sample. [source] Novel Sensitive Voltammetric Detection of Trace Gallium(III) with Presence of Catechol Using Mercury Film Silver Based ElectrodeELECTROANALYSIS, Issue 16 2009Robert Piech Abstract A new adsorptive stripping voltammetric method for the determination of trace gallium(III) based on the adsorption of gallium(III)-catechol complex on the cyclic renewable mercury film silver based electrode (Hg(Ag)FE) is presented. The effects of various factors such as: preconcentration potential and time, pulse height, step potential and supporting electrolyte composition are optimized. The calibration graph is linear from 2,nM (0.14,,g L,1) to 100,nM (6.97,,g L,1) for a preconcentration time of 30,s, with correlation coefficient of 0.9993. For a Hg(Ag)FE with a surface area of 9.7,mm2 the detection limit for a preconcentration time of 90,s is as low as 7,ng L,1. The repeatability of the method at a concentration level of the analyte as low as 0.05,,g L,1, expressed as RSD is 3.6% (n=5). The proposed method was successfully applied by studying the natural samples and simultaneous recovery of Ga(III) from spiked water and sediment samples. [source] Electroanalytical Determination of Cadmium(II) and Lead(II) Using an Antimony Nanoparticle Modified Boron-Doped Diamond ElectrodeELECTROANALYSIS, Issue 10 2009Kathryn Abstract We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by linear sweep anodic stripping voltammetry (LSASV) using an antimony nanoparticle modified boron doped diamond (Sb-BDD) electrode. Sb deposition was performed in situ with the analytes, from a solution of 1,mg L,1 SbCl3 in 0.1,M HCl (pH,1). Pb2+ inhibited the detection of Cd2+ during simultaneous additions at the bare BDD electrode, whereas in the presence of antimony, both peaks were readily discernable and quantifiable over the linear range 50,500,,g L,1. [source] A Study of Nafion-Coated Bismuth-Film Electrode for the Determination of Zinc, Lead, and Cadmium in Blood SamplesELECTROANALYSIS, Issue 21 2008Benzhi Liu Abstract In this article a sensitive differential pulse stripping voltammetry technique on Nafion-coated bismuth-film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09,,g L,1 for Cd(II), 0.13,,g L,1 for Pb(II), and 0.97,,g L,1 for Zn(II) respectively. [source] Electroanalytical Determination of Promethazine Hydrochloride in Pharmaceutical Formulations on Highly Boron-Doped Diamond Electrodes Using Square-Wave Adsorptive VoltammetryELECTROANALYSIS, Issue 18 2008Francisco, Wirley Abstract The electrochemical oxidation of promethazine hydrochloride was made on highly boron-doped diamond electrodes. Cyclic voltammetry experiments showed that the oxidation mechanisms involved the formation of an adsorbed product that is more readily oxidized, producing a new peak with lower potential values whose intensity can be increased by applying the accumulation potential for given times. The parameters were optimized and the highest current intensities were obtained by applying +0.78,V for 30 seconds. The square-wave adsorptive voltammetry results obtained in BR buffer showed two well-defined peaks, dependent on the pH and on the voltammetric parameters. The best responses were obtained at pH,4.0, frequency of 50,s,1, step of 2,mV, and amplitude of 50,mV. Under these conditions, linear responses were obtained for concentrations from 5.96×10,7 to 4.76×10,6,mol L,1, and calculated detection limits of 2.66×10,8,mol L,1 (8.51,,g L,1) for peak 1 and of 4.61×10,8,mol L,1 (14.77,,g L,1) for peak 2. The precision and accuracy were evaluated by repeatability and reproducibility experiments, which yielded values of less than 5.00% for both voltammetric peaks. The applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability, specificity, recovery and precision of the procedure in complex samples. All results obtained were compared to recommended procedure by British Pharmacopeia. The voltammetric results indicate that the proposed procedure is stable and sensitive, with good reproducibility even when the accumulation steps involve short times. It is therefore very suitable for the development of the electroanalytical procedure, providing adequate sensitivity and a reliable method. [source] The Fabrication and Characterization of a Bismuth Nanoparticle Modified Boron Doped Diamond Electrode and Its Application to the Simultaneous Determination of Cadmium(II) And Lead(II)ELECTROANALYSIS, Issue 16 2008Kathryn Abstract We report the simultaneous electroanalytical determination of Pb2+ and Cd2+ by square-wave anodic stripping voltammetry (SWASV) using a bismuth nanoparticle modified boron doped diamond (Bi-BDD) electrode. Bi deposition was performed in situ with the analytes, from a solution of 0.1,mM Bi(NO3)3 in 0.1,M HClO4 (pH,1.2), and gave detection limits of 1.9,,g L,1 and 2.3,,g L,1 for Pb(II) and Cd(II) respectively. Pb2+ and Cd2+ could not be detected simultaneously at a bare BDD electrode, whilst on a bulk Bi macro electrode (BiBE) the limits of detection for the simultaneous determination of Pb2+ and Cd2+ were ca. ten times higher. [source] Renewable Copper and Silver Amalgam Film Electrodes of Prolonged Application for the Determination of Elemental Sulfur Using Stripping VoltammetryELECTROANALYSIS, Issue 7 2008Robert Piech Abstract New, renewable copper (Hg(Cu)FE) and silver (Hg(Ag)FE) based amalgam film electrodes applied for the determination of elemental sulfur using differential pulse cathodic stripping voltammetry are presented. With surface areas adjustable from 1 to 12,mm2, both electrodes are characterized by very good surface reproducibility (,2%) and long-term stability (a few thousand measurement cycles). The mechanical refreshing of the amalgam film takes about 1,2 seconds. The effects of various factors such as instrumental parameters and the supporting electrolyte composition were optimized. Interferences from sulfides are easily removed by the addition of acid, and bubbling with argon, for Hg(Ag)FE. In the case of Hg(Cu)FE, sulfides did not interfere. The calibration graph is linear within the studied range from 16,ng L,1 to 4.8,,g L,1 for Hg(Cu)FE, and up to 6.4,,g L,1 for Hg(Ag)FE (tacc=15,s). The correlation coefficients for the two electrodes were at least 0.997. The detection limits for a low concentration of S(0) and tacc=60,s are as low as 14,ng L,1 for Hg(Cu)FE and 4,ng L,1 for Hg(Ag)FE. The proposed method was successfully applied and validated by studying the recovery of S(0) from spiked river water. [source] Properties of Poly(sodium 4-styrenesulfonate)-Ionic Liquid Composite Film and Its Application in the Determination of Trace Metals Combined with Bismuth Film ElectrodeELECTROANALYSIS, Issue 5 2008Jianbo Jia Abstract A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIMPF6) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4-styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)64,/Fe(CN)63, can be effectively improved at the PSS-BMIMPF6 modified GC. The bismuth modified PSS-BMIMPF6 composite film electrodes (GC/PSS-BMIMPF6/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS-BMIMPF6/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50,,g L,1. And the detection limits were 0.07,,g L,1 for Cd(II) and 0.09,,g L,1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120,s, respectively. Finally, the GC/PSS-BMIMPF6/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy. [source] Determination of Trace Amounts of Copper in Tap Water Samples with a Calix[4]arene Modified Carbon Paste Electrode by Differential Pulse Anodic Stripping VoltammetryELECTROANALYSIS, Issue 10 2007Çelik Canpolat Abstract A calix[4]arene modified carbon paste electrode was used for trace determination of copper. The study of the preconcentration of copper as well as the other heavy metal ions at the modified electrode, with subsequent measurement by differential pulse anodic stripping voltammetry (DPASV), indicates the efficient open-circuit accumulation of the analytes onto the electrode. Many parameters such as the composition of the paste, pH, preconcentration time and stirring rate influence the response of the measurement. The procedure was optimized for copper determination. For a 10-minute preconcentration time at pH,6.5,7.5, the detection limit (LOD) was 1.1,,g L,1. The optimized method was successfully applied to the determination of copper in tap water sample by means of standard addition procedure. The copper content of the sample was comparable with the result obtained with AAS method. [source] Simultaneous Determination of Quinoline and Pyridine Compounds in Gasoline and Diesel by Differential Pulse VoltammetryELECTROANALYSIS, Issue 6 2007Leonardo Abstract The presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion,exchange resin (Amberlyte IR,120,H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion-controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF4 0.1,mol L,1) for quinoline (,1.95,V) and pyridine (,2.52,V) vs. Ag|AgCl|KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300,mg L,1 and a limit of detection (LOD) of 5.05 and 0.25,,g L,1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0±0.3 and 33.0±0.7,mg L,1 and in diesel samples yielded 80.3±0.2 and 131±0.4,mg L,1, respectively. Spike recoveries were 94.4±0.3% and 101±0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV-vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests. [source] Enhanced Resolution of Copper and Bismuth by Addition of Gallium in Anodic Stripping Voltammetry with the Bismuth Film ElectrodeELECTROANALYSIS, Issue 24 2006Chad Prior Abstract This paper presents the enhanced analysis of copper on a bismuth electrode upon addition of gallium(III). The presence of gallium alleviates the problems of overlapping stripping signals usually observed between copper and bismuth when using the Bismuth Film Electrode. In addition, it has been found that the presence of gallium improves the reproducibility of the bismuth stripping signal. Simultaneous deposition of copper and bismuth at ,1500,mV for 2,minutes in a supporting electrolyte composed of 0.1,M pH,4.75 acetate buffer with 250,,g L,1 gallium yields well resolved copper and bismuth signals when analyzed with square-wave anodic stripping voltammetry. Simultaneous analysis of copper and lead yielded linear calibration plots in the range 10 to 100,,g L,1 with regression coefficients of 0.997 and 0.994 respectively. The theoretical detection limit for copper was calculated to be 4.98,,g L,1 utilizing a 2,minutes deposition time. The relative standard deviation for a copper concentration of 50,,g L,1 was 1.6% (n=10). [source] Adsorptive Stripping Voltammetric Determination of Trace Uranium with a Bismuth-Film Electrode Based on the U(VI),U(V) Reduction Step of the Uranium-Cupferron ComplexELECTROANALYSIS, Issue 3 2006Georgia Kefala Abstract This work reports the use of adsorptive stripping voltammetry (AdSV) for the determination of uranium on a preplated rotating-disk bismuth-film electrode (BiFE). The principle of the method relied on the complexation of U(VI) ions with cupferron and the subsequent adsorptive accumulation of the complex on the surface of the BiFE. The uranium in the accumulated complex was then reduced by means of a cathodic voltammetric scan while the analytically useful U(VI),U(V) reduction signal was monitored. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3, limit of detection for uranium was 0.1,,g L,1 at a preconcentration time of 480,s and the relative standard deviation was 4.7% at the 5,,g L,1 level for a preconcentration time of 120,s (n=8). The accuracy of the method was established by analyzing a reference sea water sample. [source] Application of a Carbon Paste Electrode Modified with a Schiff Base Ligand to Mercury Speciation in WaterELECTROANALYSIS, Issue 11 2005Montserrat Colilla Abstract A carbon paste electrode, modified with benzylbisthiosemicarbazone is used for mercury speciation in water samples. Mercury ion is selectively accumulated on the electrode surface at open circuit and its analysis was performed by cyclic voltammetry or square-wave voltammetry (SWV). A detection limit of 8,,g L,1 (3,) was found for 15,min of accumulation using SWV as measurement technique. The effect of several metallic ions and organic substances on voltammetric signal is examined. For speciation purposes, a ligand competition methodology between ligands in solution and electrode is used. Model mercury complexes are characterized as a function of their dissociation kinetics. The method was applied to mercury speciation in water samples from the Jarama River in Madrid. [source] Study of the Responses of a Sonogel-Carbon Electrode Towards Phenolic CompoundsELECTROANALYSIS, Issue 9 2005Cordero-Rando, Ma del Abstract The electrochemical behavior of a sonogel-carbon electrode towards nine phenolic compounds (chloro-, nitro- and alkyl-phenols) was studied; one of them (4-chloro-3-methylphenol) was used to evaluate characteristics of the electrode, such as accumulation and cleaning procedure of the electrode surface, reproducibility of the measurements, and influence of time from fabrication on electrochemical response. A polyethyleneglycol-modified sonogel-carbon electrode was found to improve the electrochemical response towards the analyte. A linear relationship between peak height and concentration in the range 0.005,0.5,mg L,1 was obtained, with a detection limit of 2.8,,g L,1. The studies of electrochemical parameters, as well as interferences, are also included. [source] Trace Determination of Chromium by Square-Wave Adsorptive Stripping Voltammetry on Bismuth Film ElectrodesELECTROANALYSIS, Issue 21 2004Eleni Chatzitheodorou Abstract This works reports the use of adsorptive stripping voltammetry (AdSV) for the trace determination of chromium on a rotating-disk bismuth-film electrode (BFE). During the reductive accumulation step, all the chromium species in the sample were reduced to Cr(III) which was complexed with cupferron and the complex was accumulated by adsorption on the surface of a preplated BFE. The stripping step was carried out by using a square-wave (SW) potential-time voltammetric signal. Electrochemical cleaning of the bismuth film was employed, enabling the same bismuth film to be used for a series of measurements in the presence of dissolved oxygen. The experimental variables as well as potential interferences were investigated and the figures of merit of the method were established. Using the selected conditions, the 3, limit of detection for chromium was 100,ng L,1 (for 120,s of preconcentration) and the relative standard deviation was 3.6% at the 2,,g L,1 level (n=8). Finally, the method was applied to the determination of chromium in real samples with satisfactory results. [source] A Study of the Determination of Cu(II) by Anodic Stripping Voltammetry on a Novel Nylon/Carbon Fiber ElectrodeELECTROANALYSIS, Issue 7 2004A. Mylonakis Abstract In this work we report a new electrode material formed by injection-moulding of a conducting polymer consisting of carbon fibers in a Nylon matrix. This material is highly conductive, inexpensive, easy to mould in different shapes and requires minimal pretreatment. The electrode was tested as a mercury-free sensor for the trace determination of Cu(II) by anodic stripping voltammetry (ASV). The deposition and stripping behavior of copper on the conducting material was initially studied by cyclic voltammetry and the chemical and instrumental parameters of the determination were investigated. The electrode has been shown to be suitable for the determination of Cu(II) in the range 8,,g L,1 to 30,mg,L,1 (with deposition times ranging from 30,s to 10,min) with a relative standard deviation of 2.2% (at the 0.5,mg,L,1 level) and a limit of detection of 8,,g L,1 Cu(II) for 10,min of accumulation (at a S/N ratio of 5). The electrode was, finally, applied to the determination of copper in tap-water, pharmaceutical tablets and bovine serum with recoveries of 97.4, 94.9 and 93.4%, respectively [source] Effects of 4-nonylphenol on the endocrine system of the shore crab, Carcinus maenasENVIRONMENTAL TOXICOLOGY, Issue 3 2008Christina M. Lye Abstract There is a considerable body of evidence to suggest that many anthropogenic chemicals, most notably xeno-estrogens, are able to disrupt the endocrine system of vertebrates. There have been few comparable studies on the effects of exposure to these chemicals that may serve as biomarkers of endocrine disruption in aquatic invertebrate species. In addition, the evidence available is complex, conflicting, and far from conclusive. The present study aimed to investigate the impact of the xeno-estrogen 4-nonylphenol (4-NP, nominal concentrations 10,100 ,g L,1) on the regulation and functioning of the endocrine system of the shore crab Carcinus maenas. It also set out to establish whether 4-NP are causing the effects (i.e., changes of exoskeletons including secondary sexual characteristics, pheromonally mediated behavior and ecdysone levels, and the presence of vt in the male hepatopancreas) found recently in wild shore crabs (Lye et al.,2005). The study utilizes morphological (e.g., gonadosomatic and hepatosomatic indices) and hormonal (ecdysteroid moulting hormone levels and the induction of female specific proteins, vitellins) biomarkers using radioimmunoassay and an indirect enzyme linked immunosorbent assay applied to the soluble protein fraction of adult male hepatopancreatic homogenates. Exposure of C. maenas to an effective concentration as low as 1.5 ,g L,1 4-NP resulted in a reduced testis weight, increased liver weight, and altered levels of ecdysone equivalents compared to controls. Induction of vitellin-like proteins was absent in all samples tested. The ecological implications and the possible mechanisms for the action of 4-NP on the response of the shore crab to xeno-estrogen exposure are discussed. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Oral toxicity of the cyanobacterial toxin cylindrospermopsin in mice: Long-term exposure to low dosesENVIRONMENTAL TOXICOLOGY, Issue 6 2006A. Sukenik Abstract The hepatotoxin cylindrospermopsin, a sulfated-guanidinium alkaloid with substituted dioxypyrimidine (uracil) moiety, was isolated from several cyanobacteria species. The acute toxicity of cylindrospermopsin was well established based on intraperitoneal and oral exposure; however, only a few long-term subacute exposure studies were performed to permit a reliable guideline value for cylindrospermopsin in drinking water. In the study reported herein, female and male mice were exposed to cylindrospermopsin in their drinking water. Cylindrospermopsin-containing, Aphanizomenon ovalisporum (cyanobacterium)-free medium was provided as the only source of drinking water, whereas a control group was given a fresh medium for cyanobacteria as drinking water. Over a period of 42 weeks, experiment groups were exposed to cylindrospermopsin concentration, gradually increased from 100 to 550 ,g L,1 (daily exposure ranged between 10 and 55 ,g kg,1 day,1). Body and organ weights were recorded, and serum and hematology analyses were performed 20 and 42 weeks after the beginning of the experiment. The most pronounced effect of cylindrospermopsin was elevated hematocrit levels in both male and female mice after 16 weeks of exposure to cylindrospermopsin. The observed changes in the hematocrit level were accompanied by deformation of red blood cells, which were changed into acanthocyte. Based on these results, a daily cylindrospermopsin dose of 20 ,g kg,1 day,1 (equivalent to 200 ,g L,1) is proposed as the lowest-observed-adverse-effect level for both male and female mice. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 575,582, 2006. [source] Seasonal production and molecular characterization of microcystins in Oneida Lake, New York, USAENVIRONMENTAL TOXICOLOGY, Issue 3 2005Amber Hotto Abstract Oneida Lake, northeast of Syracuse, New York, in the United States, is a shallow eutrophic lake with a well-established toxic cyanobacterial population. Samples for DNA, toxin, and phycological analyses were collected from six stations throughout the summers of 2002 (78 samples) and 2003 (95 samples). DNA was amplified by PCR using primer sets specific to the nonribosomal microcystin synthetase complex (mcyB and mcyD). PCR analysis in 2002 indicated that the microcystin genes were present in the water column from mid-June through October, as 88% of the samples tested positive for mcyB and 79% of the samples tested positive for mcyD. In both years the onset of microcystin production was detected as early as mid-July by the protein phosphatase inhibition assay, reaching a maximum in 2002 of 2.9 ,g L,1 and in 2003 of 3.4 ,g L,1. Beginning in mid- to late August of both years the microcystin level at all six stations was in excess of the World Health Organization (WHO) advisory level of 1.0 ,g L,1. In the present study we compared microcystin occurrence and potential production at the six stations using protein phosphatase inhibition assay, high-performance liquid chromatography, and polymerase chain reaction analyses. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 243,248, 2005. [source] Comparative study of microcystin-LR-induced behavioral changes of two fish species, Danio rerio and Leucaspius delineatusENVIRONMENTAL TOXICOLOGY, Issue 6 2004Daniela Baganz Abstract The spontaneous locomotor behavior separated into day/night activity phases of two fish species Danio rerio and Leucaspius delineatus was recorded and quantified continuously under sublethal long-term exposure to microcystin-LR in tanks. Microcystin-LR was applied in concentrations of 0.5, 5, 15, and 50 ,g L,1. By using an automated video-monitoring and object-tracing system, the average motility (swimming velocity) and the average number of turns were assessed. Clear dose-dependent effects of microcystin-LR on the behavior of both test fish were measured. During the daytime, the motility of Danio rerio as well as Leucaspius delineatus increased significantly by exposure to the lowest concentrations, whereas higher concentrations led to significantly decreased motility. Influenced by microcystin-LR, the swimming time of Leucaspius delineatus reversed, going from a prominently diurnal activity to a nocturnal one; Danio rerio remained active during the daytime. Most of the relative changes in the behavioral patterns of Danio rerio and Leucaspius delineatus suggest these fish have comparable susceptibility to microcystin-LR and may indicate some adverse consequences for fish populations, for example, in connection with reproduction and predator,prey interactions. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 564,570, 2004. [source] Toxicity of arsenic species to Lemna gibba L. and the influence of phosphate on arsenic bioavailabilityENVIRONMENTAL TOXICOLOGY, Issue 1 2004Martin Mkandawire Abstract The toxicity of arsenic (As) species to Lemna gibba L. and the influence of PO on As bioavailability and uptake were tested in batch culture. L. gibba were exposed to six test concentrations of NaHAsO4 · 7H2O and NaAsO3, with 0, 0.0136, 13.6, and 40 mg L,1 KH2PO4. In batch culture As toxicity to L. gibba did not relate linearly to As concentration. The growth rate, related to frond number as recommended by OECD and ISO/DIN, was significantly inhibited in fronds exposed to 20,50 ,g L,1 As(III) compared with fronds exposed to As(V). The growth rate was stimulated when plants were exposed to 50,250 ,g L,1 of both As(III) and As(V). After exposure to 300,800 ,g L,1 growth inhibition was significantly higher for As(III) than for As(V), whereas above 800 ,g L,1 As(V) was inhibited the most. The bioaccumulation of As(III) and As(V) was significantly higher for P-deficient cultures (0.98 ± 0.08 and 1.02 ± 0.19 g kg,1, respectively for 0.0136 mg L,1 PO) than for P-sufficient cultures (243 and 343 mg kg,1 for 40 mg L,1, respectively). Plants exposed to As(V) had uptake and accumulation values slightly higher than did plants exposed to As(III). No significant differences in bioaccumulation were found between plants exposed to a concentration of As(III) >1 mg L,1 and those exposed to As(V) at the same concentration. This indicates a direct relationship to P content in the culture. Toxicity may result from the uptake of As(V) instead of PO as a result of ion competition during uptake because of close thermodynamic properties, which may change the interaction among components in the media. The toxicity pattern is interpreted as a manifestation of changing speciation in the batch culture and of the oxidation of As(III) to As(V) in an oxygen-rich environment. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 26,34, 2004. [source] | ||||||||||||||||||||||||||||||||||||||||