1,721,019 research outputs found
Discussion of "Heroin, morphine, and hydromorphone determination in postmortem material by high performance liquid chromatography" [letter; comment]
No full text(On HPLC isolation and identification oh heroin and 6-monoacetylmor.) Letter to the Editors.
No full textThe local approach combined with a FE modeling technique for fatigue analysis of a steel tubular fillet-welded joint
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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
Liquid chromatography with pre-column dansyl derivatisation and fluorimetric detection applied to the assay of morphine in biological samples
No full textA simple method employing pre-column dansylation and liquid chromatography is proposed for a very sensitive and specific assay of morphine in biological samples. Nalorphine is used as an internal standard. The detection limit is 0.2 picomol of injected morphine. In the assay of human sera spiked with 150 nmol/l, the intra- and inter-assay coefficients of variation were 3.7% (n = 10) and 4.5% (n = 10), respectively. No interferences were observed from more than 70 opiate and non-opiate drugs. Urine, plasma and total blood were assayed, using different extraction methods, with negligible interference from coextractives
Collisional spectroscopy for unequivocal and rapid determination of morphine at ppb level in the hair of heroin addicts
No full textA new analytical procedure for the identification of morphine in the hair of heroin addicts has been developed using collisional spectroscopy, on a commercially available, reverse geometry, double focusing instrument. Either collision-induced dissociation (B/E = const) linked scans or mass analysed ion kinetic energy spectra lead to an unequivocal and rapid determination of morphine in hydrolysed hair extract which may be compared with the data obtained by different and more traditional analytical methods
Development of post-column enzymic reactors with immobilized alcohol oxidase for use in the high-performance liquid chromatographic assay of alcohols with electrochemical detection
No full textThe development of a very sensitive, direct injection high-performance liquid chromatographic method, using a post-column reactor with immobilized alcohol oxidase, was undertaken with the aim of determining methanol and ethanol levels in microlitre volumes of biological samples. After reversed-phase chromatography to separate methanol and ethanol, the analytes were enzymically converted into the respective aldehydes with formation of stoichiometric amounts of hydrogen peroxide, which could be measured via electrochemical oxidation at a platinum electrode. Some problems were encountered in the development of solid-phase enzymic reactors, using a delicate enzyme, that is prone to lose activity, such as alcohol oxidase. Owing to the slightly alkaline pH required for the optimum activity of alcohol oxidase, polymeric columns seemed to be preferable for the chromatography. HEMA copolymer was chosen as the stationary phase, but the methanol and ethanol peaks eluted close together and posed severe problems of limiting post-column band spreading. Reactors based on coarse supports for enzyme immobilization gave unacceptable band spreading, causing the methanol and ethanol peaks to overlap. On the other hand high-performance liquid chromatographic packings maintained the efficiency of the chromatographic separation, quite independently of the reactor volume. Polymeric supports proved superior to silicas in maintaining the enzyme activity. However, relevant changes in the enzyme substrate specificity were observed after immobilization
Direct injection high-performance liquid chromatographic assay of morphine with electrochemical detection, a polymeric column and an alkaline eluent
No full textA simple method is described for the direct determination of morphine in untreated plasma or serum, using reversed-phase high-performance liquid chromatography with amperometric electrochemical detection. A basic eluent [0.05 mol/l phosphate buffer-isopropanol-tetrahydrofuran (88:10:2) (pH 9.5)] allows both reversed-phase chromatography of morphine under ionization control conditions and its detectability at an unprotected thin-layer glassy carbon electrode at a potential of 350 mV (vs. an Ag/AgCl reference electrode). In addition, the alkaline mobile phase promotes the ionization of serum proteins, which, being poorly retained by the hydrophobic column packing [poly(styrene-divinylbenzene) copolymer], elute early in the chromatogram, leaving a clean baseline. Up to 50 microliters of simply filtered plasma can be injected. The absolute limit of detection is 0.75 ng on-column. No interferences were observed from more than 80 opiate and non-opiate drugs. The intra- and inter-assay relative standard deviations (n = 5) were 3.2 and 6.6%, respectively, at a morphine concentration of 100 ng/ml in plasma and 0.09 and 4.2%, respectively, at the level of 500 ng/ml
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