1,721,017 research outputs found
Simultaneous determination of halogenated contaminants (PCBs and PCNs) and polycyclic aromatic hydrocarbons (PAHs) in biota integrated into a single method
Full text linkIn this study, a novel analytical approach for the simultaneous determination of 127 polychlorinated biphenyls (PCBs), together with 6 polychlorinated naphthalenes (PCNs) and 16 polycyclic aromatic hydrocarbons (PAHs) was developed and validated.
The number of environmental contaminants which undergo legislation continues to increase, fostering the development and validation of sensitive, selective, fast and inexpensive analytical methods.
The determination of such analytes often requires long and expensive procedures for each class of compounds. This does not allow the rapid and fast analysis of large quantity of samples for food safety screening purposes.
The aim of this study was to develop a method for the simultaneous determination of PCBs, PCNs and PAHs in biological samples (bivalves tissues) from extraction to instrumental analysis.
The method uses pressurized liquid extraction (PLE), gel permeation chromatography (GPC) for lipid fraction removal, automatic preparative liquid chromatography for the clean-up and a single run in HRGC-LRMS.
We integrate analyses of these three groups of POPs into a single analytical protocol from sampling to injection. Not only does this method a lower amount of sample and less time, but it also allows one to increase the sample throughput.
The use of one single pre-analytical method allows one to simplify the procedures and save time, while the single run in GC-MS enables the collection of more data simultaneously and in less time (about 75 minutes for 149 analytes) compared to separate analyses
Brominated Flame Retardants in edible bivalves: food control and lack of specific legislation
Full text linkPolybrominated diphenyl ethers (PBDEs) are among the most important classes of additive brominated flame retardants (BFR). They have been identified in every compartment of aquatic ecosystems, from abiotic to biotic matrices, and in industrialized areas as well as in remote ones. PBDEs are persistent, highly bioaccumulative and can move up to high trophic levels through biomagnifications [1].
Due to the growing concern about the potential health risks of PBDEs, their characterization in biological organisms that are widely and frequently consumed as food is paramount. Furthermore, at present there is no local or international regulatory limit for PBDEs in food.
We investigated the spatial distribution and levels of PBDEs in two bivalve species (Mytilus galloprovincialis and Ruditapes philippinarum) sampled from the north-western coast of the Adriatic Sea, that are widely used in the regional cuisine. Analyses were carried out using analytical protocols already developed in the laboratory [2] and were performed by HRGC/HRMS for the simultaneous determination of 14 PBDE congeners in biota tissues. Quantifications were carried out by isotope dilution.
The total concentrations ranged from 0.003 ng g-1 wet weight to 6.66 ng g-1, with strong variations within the same sampling site. No significant differences between species were found. As for decabrominated diphenyl ether, in literature the determination of the BDE-209 is often neglected. However, the results of this study show that Deca-BDE is one of the most abundant congeners. However high, the levels of PBDEs in the samples collected near an industrial area subject to a fishing ban are lower than the values of four edible samples gathered in aquaculture farms and intended for human consumption. The concentrations of ΣPBDEs detected in this study are relatively higher than those reported for the Mediterranean area.
Considering the potentially toxic effects of PBDEs and the lack of specific legislation, this study emphasizes the need to further investigate these compounds and to establish maximum levels in foodstuff.
This work was funded by the Italian Ministry of Education, Universities and Research (MIUR) through the project PRIN (Prot. 2010AXENJ8).
[1] C.A. de Wit, Chemosphere 46 (2002) 583-624.
[2] S. Pizzini et al., Microchemical Journal 121 (2015) 184-191
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
Variations 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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Quality by Design meets combination drugs: simultaneous determination of captopril, hydrochlorothiazide and their impurities by capillary electrophoresis
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Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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