1,720,966 research outputs found
Comparison of two analytical methods for the determination of organotin compounds in marine organisms
No full textPassive sampling and stir bar sorptive extraction for the determination of endocrine disrupting compounds in water by GC-MS
No full textA new method using the extraction and preconcentration capabilities of stir bar sorptive extraction, combined with high-resolution gas chromatography and mass spectrometry, was developed for the determination of five selected endocrine-disrupting compounds (4-n-nonylphenol, bisphenol A, estrone, 17β-estradiol, and 17α-ethinylestradiol) in water. In situ derivatization to transform the phenolic compounds into lipophilic and volatile analytes was carried out with acetic anhydride. Two different methods of headspace derivatization to further improve the chromatographic properties of 17β-estradiol and 17α-ethinylestradiol were developed and compared.
The optimized method provided good sensitivity (limits of
quantitation 1.2–2.6 ng), repeatability (relative standard
deviation 2–9%), and reproducibility (relative standard
deviation 10–17%). Passive sampling by means of polar
organic chemical integrative samplers was applied to monitor river waters used as supply sources for drinking water treatment plants in the Liguria region of Italy. The analytes showed a different distribution at the three sites considered; bisphenol A proved to be the most abundant, ranging from 185 to 459 ng per sampler
Multivariate optimization approach for the analysis of butyltin compounds in mussel tissues by gas chromatography-mass spectrometry
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Determination of endocrine disrupting compounds in drinking waters by fast liquid chromatography-tandem mass spectrometry
No full textGrowing attention has been recently paid to safety of food and drinking water, making necessary the adoption of policies for water sources protection and the development of sensitive and rapid analytical methods to identify micropollutants.
Endocrine-disrupting compounds (EDCs) have emerged as amajor issue as they alter the functioning of the endocrine system. Since ingestion of EDCs via food is considered themajor exposure route, there is a growing interest in understanding EDC fate during drinking water treatment and inmonitoring potential contamination of surface waters and groundwaters. In this work, a fast liquid chromatography–electrospray ionization–tandemmass spectrometrymethodwas developed for the determination of 4-n-nonylphenol (NP), bisphenol A (BPA), estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in drinking waters.
In the literature analytical articles seldom provide details regarding fragmentation pathways. In this paper spectra of the five EDCs in negative ESI were interpreted with the support of accurate mass spectra acquired by a quadrupole time-of-flight instrument; fragmentation pathways were also proposed. The chromatographic separation of EDCswas optimized on a Pinnacle DB Biphenylic column with awater–acetonitrile gradient.Quantitative analysiswas performed inmultiple reaction monitoring (MRM) mode using bisphenol A-d16 (BPA-d16) as internal standard; calibration curves showed good correlation coefficients (0.9989–0.9997). All figures of merit of the method were satisfactory; limits of detection were in the range 0.2–0.4 ng/ml. The method was applied to the determination of the analytes in waters sampled by polar organic chemical integrative samplers in
a drinking water treatment plant. Rather low concentration of BPA, NP and E1 were measured in the inlet, while none of theconsidered EDCs was detected in the outlet
Development of a fast liquid chromatography-tandem mass spectrometry method for the determination of endocrine disrupting compounds in waters
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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
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