1,720,971 research outputs found
Chemical Vapour Generation of Arsane in the presence of l-Cysteine. Mechanistic studies and their analytical feedback
No full textHuman exposure to thallium through tap water: A study from Valdicastello Carducci and Pietrasanta (northern Tuscany, Italy)
Full text linkA geological study evidenced the presence of thallium (Tl) at concentrations of concern in groundwaters near Valdicastello Carducci (Tuscany, Italy). The source of contamination has been identified in the Tl-bearing pyrite ores occurring in the abandoned mining sites of the area. The strongly acidic internal waters flowing in the min- ing tunnels can reach exceptional Tl concentrations, up to 9000 μg/L. In September 2014 Tl contamination was also found in the tap water distributed in the same area (from 2 to 10 μg/L). On October 3, 2014 the local authorities imposed a Do Not Drink order to the population.
Here we report the results of the exposure study carried out from October 2014 to October 2015, and aimed at quantifying Tl levels in 150 urine and 318 hair samples from the population of Valdicastello Carducci and Pietrasanta. Thallium was quantified by inductively coupled plasma — mass spectrometry (ICP-MS). Urine and hair were chosen as model matrices indicative of different time periods of exposure (short-term and long- term, respectively).
Thallium values found in biological samples were correlated with Tl concentrations found in tap water in the living area of each citizen, and with his/her habits. Thallium concentration range found in hair and urine was 1–498 ng/g (values in unexposed subjects 0.1–6 ng/g) and 0.046–5.44 μg/L (reference value for the European population 0.006 μg/L), respectively. Results show that Tl levels in biological samples were significantly associat- ed with residency in zones containing elevated water Tl levels. The kinetics of decay of Tl concentration in urine samples was also investigated. At the best of our knowledge, this is the first study on human contamination by Tl through water involving such a high number of samples
Determination of S-nitrosoglutathione in plasma: comparison of two methods.
No full textIn this work we compared the results of the GSNO determination in human plasma by two independent methods. The first method is based on the pre-column derivatization of GSNO thiolic part by p-hydroxymercury benzoate (PHMB) and followed by the determination of GS-PHMB product by reversed phase chromatography coupled to chemical vapour generation atomic fluorescence spectrometry (RPC-CVGAFS). The second method is based on RPC separation of GSNO from interfering compounds and the post-column, on-line enzymatic hydrolysis of GSNO by commercial γ-glutamyl transferase (GGT) and fluorescence detection. Endogenous GSNO was determined only in plasma from blood sampled by syringe (not by Vacutainers®) and ranged between 157 and 257 nM on the basis of RPC-CVGAFS method, and between 90 and 225 nM by RPC-FD method. There was a good correlation between the two methods (slope = 1.06 ± 0.09, R2 = 0.9543). RPC-CVGAFS method based on PHMB derivatization determined a GSNO concentration 60 ± 20 nM in excess with respect to RPC-FD method. Sampling issues connected with common blood sampling procedures like venipuncture and sampling in syringe or Vacutainers® still introduce in GSNO analysis unknown factors, which require further investigations
Determination of hydrogen sulfide and volatile thiols in air samples by mercury probe derivatization coupled with liquid chromatography-atomic fluorescence spectrometry
No full textEffect of Additives on Chemical Vapour Generation of Bismuthane by Derivatization by Tetrahydroborate(III)
No full textInfluence of environmental and anthropogenic parameters on thallium oxidation state in natural waters
Full text linkThe abandoned mining area of Valdicastello Carducci (Tuscany, Italy) is characterized by the massive presence of thallium in the acid mine drainages and in the valley stream crossing the region. We previously found that Tl(III), generally considered the less stable oxidation state of thallium, is present both in the stream and in tap water distributed in the area, whereas acid mine drainages only contain Tl(I). These findings posed some concern related to the reactivity and dispersion of this toxic element in the environment. Since the valence state of thallium determines its toxicity, distribution and mobility, the study of thallium redox speciation appears crucial to understand its environmental behaviour. In this work, water samples collected from the mine drainages and the contaminated stream were adopted as model to study the distribution of aqueous Tl(I)/Tl(III) as a function of light exposure and solution properties and composition. The influence of three light sources and organic acids was evaluated. Thallium speciation was also assessed in tap water after treatment with common oxidizing agents, and in the rust crust collected from the public waterworks
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
Determination and Characterization of Phytochelatins by Liquid Chromatography Coupled with On Line Chemical Vapour Generation and Atomic Fluorescence Spectrometric Detection
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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