1,721,067 research outputs found
Determination of furan fatty acids in extra virgin olive oil
No full textThe presence of 4 different furan fatty acids (F-acids) was detected in 18 samples of transmethylated monovarietal extra virgin olive oil: methyl 10,13-epoxy-11,12-dimethyloctadeca-10,12-dienoate [diMeF(9,5)], methyl 12,15-epoxy-13,14-dimethyleicosa-12,14-d [diMeF(11,5)] and both olefinic derivatives of diMeF(11,5) with one unsaturation on the side chains conjugated with the furan ring. Transmethylated oils were analyzed by normal phase high-performance liquid chromatography coupled on-line with capillary gas chromatography. After the gas chromatographic separation step, a more selective detection of F-acids was achieved by using a photoionization detector mounted in series with a flame ionization detector. The concentration off-acids ranged between 50 ppb (detection limit of the method) and 2.1 ppm in the oil. The olefinic derivatives of diMeF(11,5) acids detected were not artifacts created during the sample preparation or during the chromatographic analysis
Mineral oil polyaromatic hydrocarbons in foods, e.g. from jute bags, by on-line LC-solvent evaporation (SE)-LC-GC-FID
No full textOn-line and automated LC-SE-LC-GC-FID was used for the analysis of polyaromatic hydrocarbons in foods contaminated with mineral oil products. The detection limit for a fraction was around 1 mg/kg. Batching oil from jute bags introduces two-ring and three-ring aromatic compounds into foods (shown for rice), and environmental contamination of fish introduces primarily two-ring compounds. For other foods containing mineral oil material from unknown sources, the analysis provided important information about the type of oil involved (shown for a sample of linseed oil, a safflower oil and a chocolate)
On-line high-performance liquid chromatography-solvent evaporation-high-performance liquid chromatography-capillary gas chromatography-flame ionisation detection for the analysis of mineral oil polyaromatic hydrocarbons in fatty foods
No full textAn automated on-line method is described that involves a first LC separation on a large column, evaporation of a 6-ml fraction in an on-line solvent evaporator, a second LC separation using a different mobile phase, fractionating the components of interest and transfer to GC through the in-line vaporiser/overflow interface. The method is designed for the injection of a large amount of food extract (e.g. up to 200 mg of fat) and is applied to the analysis of mineral oil material in a linseed oil
Solvent Trapping during Large Volume Injection with an Early Vapor Exit, Part 3: The Main Cause for the Loss of Volatile Components during Partially Concurrent Evaporation
No full textWhen 0.53 mm i.d. uncoated precolumns connected to a solvent vapor exit are used for sample introduction with partially concurrent solvent evaporation, substantial losses of volatile solutes are often observed. They were found to be the consequence of solute accumulation at the front end of the flooded zone, which in turn is the result of a strong pressure drop over the flooded zone owing to the formation of plugs of sample liquid, The pressure drop causes significant solvent evaporation at the front, which enriches the solute material there and causes its loss. The use of 0.32 mm i.d. restrictions between the uncoated precolumn and the vapor exit greatly reduced this problem
Capacity of Uncoated 0.53 mm id Pre-Columns for retaining Sample Liquid in Presence of a Solvent Vapor Exit
No full text0.53 mm i.d. uncoated precolumns of about 10 m in length followed by a solvent vapor exit have become a standard set-up for large volume on-column injection. It went unnoticed, however, that the introduction of a vapor exit requires two modification of previous working guidelines. First, the capacity of the precolumn to retain sample liquid is increased by a factor of 2.3-3 as a result of the around 100 times higher carrier gas flow rate. Secondly, it must be considered that this gain in retention of liquid is lost again upon closure of the exit: as the gas flow rate is reduced to a few mL/min, the layer of the residual sample liquid expands about 2.3-3 times. Hence, closure should occur late, and a section of the precolumn must be assigned for this secondary spreading
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
On-line LC-solvent evaporation (SE)-LC-GC for the determination of aromatic hydrocarbons in food contaminated with mineral oil
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
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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