1,720,962 research outputs found
Ion chromatography and fluorescence detection of trace metal ions
No full textA method based on separation with ion chromatography and post-column fluorescence detection has been developed for the determination of Al(III), Cd(II), Ga(III), ln(III) and Zn(II). AI(III) and Ga(III) separation was achieved by an eluting system containing two ligands namely pyridine-2,6-dicarboxylic acid and tartaric acid. Calibration graphs were linear for at least two orders of magnitude for all analytes (10-2,000 mug/1) and detection limits ranged from 0.5 to 1.6 ng
Distribution of minor and trace metals in Carezza Lake (Antarctica) ecosystem
No full textThis paper reports the distribution of a series of metals in natural samples collected at Carezza Lake in Antarctica, during the Italian Expedition in the austral summer 1989/90. The considered elements are: water, sediments and soil sampled from the surroundings of the lake and algae. The determination of the total concentration of the following metals was performed: Al, As, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Zn. In addition, for sediment and soil samples, a speciation study was performed for some metals, namely Cd, Co, Cr, Cu, Fe, Mn, Ni, Zn, using the Tessier procedure
Mercury speciation in biological samples
No full textAn extraction method is proposed in order to evaluate mercury speciesin biological samples (e.g. fish, mushrooms). Sulphur-containing ligands have been considered and thiourea was chosen for the optimised extraction procedure according to the best recovery obtained (65.9%, 75.8%, 47.1% and 98.2% for CH3Hg+, C2H5Hg+, C6H5Hg+ and Hg2+ respectively)and the chromatographic performance. Thiourea solutions added to biological samples enabled extraction of organomercury species; the influence of reaction time and recovery yields were evaluated. The proposed procedure, coupled with an on-line preconcentration step, allows to reduce contamination problems and to obtain detection limits at ng/g levels. The method has been evaluate with reference materials (BCR)
Distribution of minor and trace metals in lake and sea environments (Antarctica)
No full textWe report the distribution of a series of metals in natural samples collected from Antarctic lakes (Carezza lake no. 3, Edmonson Point lake no. 13C, Inexpressible Island lake no. 9) during the Italian Expeditions in the austral summers 1990/91 and 1991/92. The considered elements are :water, sediments, soil sampled from the surroundings of the lake and algae, for the samplings of 1990/91, and water for the samplings of 1991/92. The determination of the total concentration of the following metals was performed: Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Pb, Si, Sr, Zn. The determination of some metals, namely Cd, Cu, Fe, Mn, Ni, was also performed on sea water samples collected in 1990/91 on one vertical profile for one off-shore Antarctic Ocean site, and on a series of sampling stations of Ross Sea Bay
Determination of copper, cadmium, iron, manganese, nickel and zinc in Antarctic seawater. Comparison of electrochemical and spectroscopic procedures
No full textDifferent procedures for the determination of ultratrace metal ions in Antarctic sea water have been adopted and critically compared. The investigated metal ions were Cd, Cu, Fe, Mn, Ni and Zn. Sea water samples were analysed with adsorptive cathodic stripping voltammetry and with graphite furnace atomic absorption spectroscopy. Different treatments, such as UV irradiation, acidification and on-line sample enrichment were adopted and the results for samples collected in different sites and on a vertical profile were discussed and compared
Ion chromatographic separation and on-line cold vapour atomic absorption spectrometric determination of methylmercury, ethylmercury and inorganic mercury
No full textThe ion chromatographic separation of methylmercury, ethylmercury and inorganic mercury as cysteine complexes was investigated. The chromatographic apparatus was interfaced with cold vapour atomic absorption spectrometry for detection using an on-line continuous flow cell coupled with a reduction system (sodium tetrahydroborate). The influence of the composition of the eluent (pH, ionic strength, cysteine concentration) and stripping gas flow-rate was investigated. The method was optimized by coupling an on-line preconcentration step. The detection limits, evaluated on 100.0-ml samples, were 2, 10 and 4 ng for Hg, CH3Hg and C2H5Hg, respectively. The method was applied to synthetic mixtures and natural samples (tap water) and furnished satisfactory results
Ion-pair reversed-phase high-performance liquid chromatography for trace metal preconcentration followed by ion-interaction chromatography
No full textIon-interaction chromatography of Plasmocorinth B (a disulphonated azo dye) complexes of Co(III), Cu(II), Fe(III), Ga(III), In(III), Ni(II), V(V) and Zr(IV) was studied. The behaviour of two different reversed-phase C18 columns (5 and 10 mum) was compared and an on-line enrichment procedure was developed following the optimization of eluent (pH, ligand concentration, ionic strength and organic modifier). The described technique, applied to the analysis of metal ions at mug/l levels in natural waters, gave satisfactory precision and accuracy in comparison with inductively coupled plasma atomic emission spectroscopic results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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