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Analytical and Bioanalytical Chemistry (v.366, #5)
»Mercury as a Global Pollutant«– The Fifth International Conference
by M. Horvat; R.-D. Wilken (pp. 415-416).
Assessing the contribution of natural sources to the global mercury cycle: The importance of intercomparing dynamic flux measurements by M. S. Gustin; S. E. Lindberg (pp. 417-422).
In order to constrain the contribution of natural sources of mercury to the global atmospheric cycle we need to: 1. assess the methods used to measure mercury flux, 2. characterize those factors most important in controlling emissions, 3. develop a database of emissions from representative locations, and 4. develop a means of scaling up measured emissions to estimate fluxes on a regional basis. This paper describes how an international multi-collaborator project, the Nevada SToRMS Project, held September 1997 in Reno, Nevada, USA, contributed to our ability to constrain natural source mercury emissions. This study entailed a field intercomparison of those methods typically applied to measure mercury flux from substrate combined with evening workshops and roundtable discussions. The project was unique in that it focused on assessing our ability to measure the flux of an environmental contaminant. This is more difficult than measurement of the concentration of a contaminant because of the number and nature of the variables which influence the field flux measurements, including experimental design, spatial heterogeneity, and temporally changing environmental conditions. As a result of the Nevada SToRMS Project, rapid and significant advances in our understanding of how to constrain emission fluxes from large areas of mercury enrichment were realized. Because this intercomparison was a multi-investigator project, the results and implications of the project have been broadly circulated. The sincere scientific collaboration that evolved amongst those working on the study has led to significant advancements in our understanding of the fate and transport of mercury in the environment.
Improved determination of gaseous divalent mercury in ambient air using KCl coated denuders by Xinbin Feng; J. Sommar; K. Gårdfeldt; O. Lindqvist (pp. 423-428).
An improved method for the determination of gaseous divalent mercury (GDM) in ambient air using KCl coated denuders has been developed and tested. GDM collected in the KCl coated denuders can be quantitatively desorbed at 450 °C in 10 min. After being complete thermally reduced to Hg0 at 900 °C, all mercury released from the denuder is pre-concentrated on the analytical Au trap, and detected by cold vapor atomic fluorescence spectrometry (CVAFS). The absolute detection limit of the method is less than 3 pg. Preliminary data of GDM concentration in ambient air from different sampling stations show that GDM concentrations in the urban air of Göteborg are much higher than in rural air (Rörvik and Sasetta), which indicates the anthropogenic origin of GDM.
Mercury measurements in ambient air near natural gas processing facilities by Zdravko Špirić; Nikolai R. Mashyanov (pp. 429-432).
Natural gas from gas fields around the globe often contains mercury, along with a large number of other harmful substances (CO2, H2S, RSH, COS, etc). Mercury’s potentially harmful effect on humans and on the ecological system as a whole as well as the technological risk regarding very sophisticated and expensive process equipment and catalysts make its removal imperative. There is a need for the highest efficiency for mercury removal and for permanent improvement and enhancement of technological and control procedures, including analytical instruments and measurements.Mercury concentration measurements in the ambient air performed during natural gas processing confirm that the design of the system at the Molve gas plant is adequate to meet the mercury removal objectives. The obtained results also illustrate in an excellent way the use of the portable instrument to identify and prevent potential mercury generated hazards linked to specific industrial processes.
Clean conditions for the determination of ultra-low levels of mercury in ice and snow samples by C. P. Ferrari; A. L. Moreau; C. F. Boutron (pp. 433-437).
Laboratory facilities and methods are presented for the determination of ultra-low levels of mercury (Hg) in ice and snow samples originating from polar ice caps or temperate regions. Special emphasis will be given to the presentation of the clean laboratory and the cleaning procedures. The laboratory is pressurized with air filtered through high efficiency particle filters. This first filtration is not enough to get rid of contamination by Hg in air. Experiments are conducted in a clean bench, especially built for Hg analysis, equipped with both particle filter and activated charcoal filter. It allows to obtain very low levels of atmospheric Hg contamination. Ultrapure water is produced for cleaning all the plastic containers that will be used for ice and snow samples and also for the dilution of the standards. Hg content in laboratory water is about ¶0.08 ± 0.02 pg/g. A Teflon system has been developed for the determination of Hg in ice and snow samples based on Hg(II) reduction to Hg(0) with a SnCl2/HNO3 solution followed by the measurement of gaseous Hg(0) with a Hg analyzer GARDIS 1A+ based on the Cold Vapor Atomic Absorption Spectroscopy method. Blank determination is discussed.
Analysis and stability of mercury speciation in petroleum hydrocarbons by N. S. Bloom (pp. 438-443).
Raw petroleum and natural gas often contain high concentrations of mercury, which can be damaging to the metal components of production facilities, as well as to the environment. Various Hg species have different properties in terms of mobility, reactivity and bioavailability. Thus, for cost-effective decisions regarding plant design, Hg extraction, and pollution control, speciation information must be available at the production facility. In this paper, a simple, wet chemical speciation method, which provides data on Hgo, dissolved and particulate total Hg, Hg(II), and methyl Hg is presented. The method incorporates species-specific extraction and separation procedures, followed by cold vapor atomic fluorescence spectrometry (CVAFS). For each species, detection limits of approximately 0.1 ng/g were obtained. Storage experiments in various containers showed that organo-mercury species were stable for at least 30 days in all containers except those made of polyethylene; and Hgo was stable in all containers except those made of stainless steel or polyethylene. Hg(II) was rapidly lost from all containers except those made of aluminum, which rapidly converted it to Hgo, which was stable. In general, most of the total Hg in petroleum products was particulate Hg, followed by dissolved Hg(II) and Hgo. Sub-ng/g concentrations of methyl-Hg were observed in most samples.
Gold electrodes from recordable CDs for mercury quantification by flow injection analysis by E. M. Richter; M. A. Augelli; G. H. Kume; R. N. Mioshi; L. Angnes (pp. 444-448).
The development of a new methodology for the construction of very efficient flow cells for mercury detection by potentiometric stripping analysis, employing the thin gold layer of recordable CDs as working ¶electrode is reported. This new source of electrodes (CDtrodes) show very attractive performance, similar to that obtained with commercial gold electrodes, with superior versatility. The low cost of this new source of “gold electrodes” allows a frequent replacement of the electrode, avoiding cumbersome clean-up treatments. Various experimental parameters have been optimized to yield low detection limits (0.25 ng/mL of mercury for 5 min deposition at 0.3 V) and good precision (standard deviation of 1.9% was obtained for 15 repetitive measurements using 10 ng/mL of mercury). Standard curves were found to be linear over the range of 0.5–100 μg L–1 of mercury. The flow cells developed were used for the quantification of mercury in oceanic and tap water.
Analytical validity of the determination of mercury in whole blood and urine – Results of the German external assurance programme for toxicological analysis in biological materials by K. H. Schaller; D. Weltle; J. Angerer (pp. 449-452).
The determination of mercury concentrations in blood and urine is currently the best way of monitoring individual uptake of organic and inorganic mercury. In Germany these determinations must be carried out under the conditions of an external quality assurance programme. The German performance evaluation, based on reference values established by reference laboratories yields success rates in percent for the participants in the intercomparison programme of about 60%. A Canadian evaluation system based on two evaluations scores, yields success rates of 25–50% for “good performance” and of 65–80% for “acceptable performance”. The determination of mercury in blood and urine is at present not carried out with the necessary reliability.
A methodological study of mercury speciation using Dogfish liver CRM (DOLT-2) by M. Logar; M. Horvat; I. Falnoga; V. Stibilj (pp. 453-460).
The purpose of the study was to optimise analytical methods for determination of the chemical speciation of mercury in studies of protective mechanisms of selenium. Optimisation of the methods was performed using CRM DOLT-2 (Dogfish liver), both in its original form and after separation of various fractions. The sample was homogenised with 10 mM Tris-HCl buffer (pH 7.6) and ultracentrifuged. The soluble phase obtained was applied to a size exclusion chromatography column (Sephadex ¶G-75 column) for separation of various protein fractions. Total mercury (total Hg), monomethyl mercury (MeHg) and selenium (Se) were determined in whole dogfish liver tissue and its soluble and insoluble phases (pellet). Different approaches for determination of total Hg and MeHg were compared. Simultaneous determination of MeHg and inorganic mercury (Hg2+) was based on alkaline dissolution and/or acid leaching, followed by ethylation, room temperature precollection, isothermal gas chromatography (GC), pyrolysis and detection with cold vapour atomic fluorescence spectrometry (CVAFS). The sum of MeHg and Hg2+ was compared to total Hg results obtained by acid digestion and CVAAS detection. The accuracy of MeHg determination was checked by its determination using acid leaching at room temperature, solvent extraction, back extraction into Milli-Q water, ethylation, GC and CVAFS detection. For the insoluble phase it is recommended to use solvent extraction for MeHg and acid digestion CVAAS for total Hg. For determination of MeHg and Hg2+ in the lyophilised sample and water soluble fractions containing low concentrations of mercury species, the simultaneous measurement of MeHg and Hg2+ after alkaline dissolution is the most appropriate method.
A low-cost non instrumental method for semiquantitative determination of mercury in fish by A. V. Yallouz; R. Calixto de Campos; S. Paciornik (pp. 461-465).
A non instrumental method for the semiquantitative determination of mercury in fish is described. The sample is acid digested and the mercury vapor released after chemical reduction with SnCl2. The mercury vapor is then collected on a detecting paper covered with an emulsion of Cu2I2, 3% carboxymethylcellulose and MgCl2 as moistener agent. The colored Cu2[HgI4] complex is formed and the color intensity is proportional to the mercury concentration in the original sample. Parameters such as sample mass/digestion solution volume ratio, emulsion composition, paper covering technique, carrier gas flow were investigated. Comparative studies using CVAAS and digital color analysis after scanning the papers confirmed the applicability of the method to real samples.
Determination of methylmercury in fish tissue by gas chromatography with microwave-induced plasma atomic emission spectrometry after derivatization with sodium tetraphenylborate by H. E. L. Palmieri; L. V. Leonel (pp. 466-469).
The detection of methylmercury species (MeHg) in fish tissue was investigated. Samples were digested with KOH-methanol and acidified prior to extraction with methylene chloride. MeHg was back-extracted from the organic phase into water. An aliquot of this aqueous solution (buffered to pH 5) was subjected to derivatization with sodium tetraphenylborate (NaBPh4) and then extracted with toluene. The organic phase containing MePhHg was injected into a gas chromatograph (GC) which is on-line with a microwave-induced plasma atomic emission spectrometer (MIP-AED). The quantification limit was about 0.6 μg/g and 0.1 μg/g of MeHg (as Hg) for 0.08 g of freeze-dried fish powder and 0.5 g of fresh samples, respectively. Two certified reference materials, CRM 464 (tuna fish) from Community Bureau of Reference-BCR and DORM-2 (dogfish muscle) from National Research Council Canada-NRC were selected for checking the accuracy of the method. This methodology was applied to the determination of MeHg in some kinds of fish from ¶the Carmo river with alluvial gold recovery activities (“garimpos”) in Mariana, Minas Gerais, Brazil.
Discovery of a transalkylation mechanism – Identification of ethylmercury+ at a tetraethyllead-contaminated site using sodiumtetrapropylborate, GC-AED and HPLC-AFS by M. Hempel; J. Kuballa; E. Jantzen (pp. 470-475).
Although organolead as a gasoline additive is banned in most countries, contamination by organolead compounds is still present. Little is known about transformation reactions of organolead compounds and especially transalkylation reactions with other metals. Laboratory experiments to clarify transalkylation reactions between organolead and inorganic mercury, and investigations of sites, where organolead compounds were emitted, are reported. Under laboratory conditions, inorganic mercury is ethylated to ethylmercury+ in presence of tetraethyllead. These transalkylations take place very fast and almost completely. In soil samples from an industrial site contaminated with organolead compounds and inorganic mercury, EtHg+ was clearly identified in high concentrations (up to 46 mg Hg/kg dw). Furthermore, methylmercury+ was found in concentrations up to 27 mg Hg/kg dw. It is the first time, that a transethylation of an organolead compound to an organomercurial compound in the environment is reported. It must be assumed, that this transalkylation takes place at sites, where organolead compounds occur and Hg2+ is available. Thus, it will be necessary to assess the risk of these sites.
Optimization of HPLC-ICP-AES for the determination of arsenic species by M. Chausseau; C. Roussel; N. Gilon; J. M. Mermet (pp. 476-480).
High performance liquid chromatography coupled to ICP-AES detection provides a rapid, reliable and sensitive method for arsenic speciation. The separation of As(III), As(V), DMA and MMA was achieved with ion exchange chromatography coupled to an axially-viewed sequential ICP-AES. After optimization of the chromatographic parameters (pH and concentration of the mobile phase), a careful study of the interface was conducted. Five nebulizers associated to three spray chambers were tested. Response of the ICP to each arsenic species was strongly affected by the selection of the nebulizer and spray chamber, however similar responses were obtained for each arsenic species. Best signal-to-noise ratios were obtained by using a microconcentric nebulizer and a cyclone spray chamber and did not affect the chromatographic resolution. Detection limits better than 10 μg L–1 were obtained for As(III), DMA, MMA and 20 μg L–1 for As(V), which is a significant improvement over previously published results.
Fiber-optic microsensor for high resolution pCO2 sensing in marine environment by G. Neurauter; I. Klimant; O. S. Wolfbeis (pp. 481-487).
A fast responding fiber-optic microsensor for sensing pCO2 in marine sediments with high spatial resolution is presented. The tip diameter varies typically between 20 and 50 μm. In order to make the pH-indicator ¶8-hydroxypyrene-1,3,6-trisulfonate soluble in the ethyl cellulose matrix, it was lipophilized with tetraoctylammonium as the counterion [HPTS-(TOA)4]. The microsensor was tuned to sense very low levels of dissolved carbon dioxide which are typically present in marine systems. The detection limit is 0.04 hPa pCO2 which corresponds to 60 ppb CO2 of dissolved carbon dioxide. A soluble Teflon derivative with an extraordinarily high gas permeability was chosen as a protective coating to eliminate interferences by ionic species like chloride or pH. Response times of less than 1 min were observed. The performance of the new microsensor is described with respect to reproducibility of the calibration curves, dynamic range, temperature behavior, long term stability and storage stability. The effect of hydrogen sulfide as an interferent, which is frequently present in anaerobic sediment layers, was studied in detail.
Analysis of low molecular weight organic acids in water with capillary zone electrophoresis employing indirect photometric detection by J. Dahlén; J. Hagberg; St. Karlsson (pp. 488-493).
A capillary zone electrophoretic method for the analysis of low molecular weight carboxylic acids in water was developed. The application uses the chromophore trimellitic acid that allows for indirect photometric detection at 254 nm. Selectivity control by the addition of Ca2+ to the carrier electrolyte made possible a baseline resolved separation of 14 carboxylic acids. Good linearity and repeatability were obtained for both electrokinetic and hydrostatic injection modes. The usefulness of the method is demonstrated by the analysis of a snow sample.
Determination of Al, Cu, Li and Mn in spruce seeds and plant reference materials by slurry sampling graphite furnace atomic absorption spectrometry by C. Engelsen; G. Wibetoe (pp. 494-503).
An ultrasonic slurry sampling graphite furnace AAS method was developed for the determination of Al, Cu, Li and Mn in spruce seeds, NBS SRM 1575 pine needles and GBW CRM 07602 bush branches and leaves. The only sample preparation was grinding in a Mixer Mill before preparing a slurry by adding 0.14 mol/L nitric acid to a small sample aliquot. Cryogenic grinding was used for the spruce seeds to solve the problem of agglomerating during grinding at room temperature. A modified sample tray was applied allowing the use of both the commercial 1.5 mL vials and home-made 15 mL vials. With optimal conditions for ultrasonic agitation the homogeneity and particle size distributions in the slurries prepared in the two different vials were similar. Several aspects of the slurry sampling approach are discussed and data of important parameters are given, including the total number of particles injected into the graphite furnace, densities of the materials and percentage of analyte extracted into the liquid phase of the slurry. The density of the materials was determined by two methods; by using a Coulter particle analyser and by using a gravimetric method. The two methods gave similar accuracy and precision. The concentration ranges of the elements (in μg g–1) were: 80–2100 for Al, 3–15 for Cu, 0.06–2.5 for Li and 50–700 for Mn. External calibration with aqueous standards was employed. Chemical modifiers were not found to be necessary. The relative standard deviations were in the range 1.7–7%. Analyses of the two certified plant reference materials confirmed the accuracy of the method. In addition no significant difference was found for analyses of digested and slurried spruce seeds. The detection limit was 10 ng g–1 for Li and 170 ng g–1 for Cu. The characteristic mass (area measurements) was 4.4 pg for Li and 11 pg for Cu. For Al and Mn less sensitive wavelengths were used.
Cationic cyanine as a near-infrared fluorescent probe for the determination of nucleic acids by Hong Zheng; Dong-Hui Li; Chang-Qing Zhu; Xiao-Lan Chen; Jin-Gou Xu (pp. 504-507).
A new method with a cationic near-IR cyanine as fluorescent probe was developed for the determination of nucleic acids. The near-IR cyanine shows maximum excitation and emission wavelengths at 765 and 790 nm, respectively, in aqueous solution. The method is based on the fluorescence decrease of near-IR cyanine in the presence of nucleic acids. Under optimal conditions, the ratio of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of ¶nucleic acids over the range 0.10–1.2 μg/mL for CT (calf thymus) DNA or SM (salmon sperm) DNA, and 0.10–¶1.6 μg/mL for yeast RNA. The detection limits were ¶30 ng/mL for CT DNA, 25 ng/mL for SM DNA and ¶70 ng/mL for yeast RNA. The relative standard deviation (n = 6) was 2.1% for 500 ng/mL CT DNA, 2.4% for ¶500 ng/mL SM DNA and 2.7% for 500 ng/mL yeast RNA, respectively.
New strategy for the determination of microcystins and diarrhetic shellfish poisoning (DSP) toxins, two potent phosphatases 1 and 2A inhibitors and tumor promoters by C. Hummert; M. Reichelt; B. Luckas (pp. 508-513).
A new analytical strategy was established to improve the determination and identification performance during analyses of microcystins and diarrhetic shellfish poisoning (DSP) toxins in different matrices. Automated high performance size exclusion chromatography (gel permeation chromatography, SEC) was applied for the clean-up of raw extracts from algae and mussel tissue containing either microcystins or DSP toxins. The cleaned raw extracts are well suited for the direct determination of microcystins and DSP toxins by HPLC/MS. The analyses of cleaned raw extracts containing microcystin by HPLC and UV/diode array detection (DAD) revealed chromatograms without interfering peaks. Additionally, methods for the identification of unknown microcystins and those not available as standards were developed and established. The proposed strategy is exemplarily demonstrated for the analyses of a natural algae community from a lake in Slowakia and a naturally contaminated mussel from Portugal.