1,720,968 research outputs found
Nanostructured Au/Ti bimetallic electrodes in selective anodic oxidation of carbohydrates
No full texthe anodic oxidation of species possessing potentially oxidisable functionalities has been studied on a non conventional electrode system based on a Ti substrate partially coated by electrodeposited Au nanoparticles. The results show that the electrocatalytic behaviour of the Au nanoparticles, in the frame of such a bimetallic system, is very different from that of pure Au. In particular, catalytic synergy between Au and Ti leads to the electro-oxidation of aldoses and aldehydes, while ketoses and monohydric alcohols result electrochemically inert. A different behaviour has been observed in the case of bulk Au surface: all the species under investigation undergo oxidation, so that no selectivity is activated. A correlation is found between the actual electroactivity and the nature of the functional group, when considered together with the chemical structure of the molecule
Preliminary evaluation of the use of a disposable electrochemical sensor for selective identification of Δ9-tetrahydrocannabinol and cannabidiol by multivariate analysis
No full textThe widespread diffusion of products deriving from Cannabis sativa L. led to the necessity of rapid and reliable
methods for the identification of samples containing Δ9-tetrahydrocannabinol (THC), the psychoactive component
of the plant, which imparts mental distortions and hallucinations. Although some efficient electrochemical
sensors have been already proposed for such a purpose, they do not consider that the plant may also contain huge
amounts of cannabidiol (CBD), which possesses an electroactive moiety quite similar to that of THC. The definition
of both THC and CBD concentration is at the basis of discrimination between recreational-type and fibretype
cannabis samples; detection of these species is not only important in vegetable samples but also in relevant
commercial products and in biological fluids. We proposed here a screen-printed electrode coated with a layer of
carbon black for the rapid identification of samples containing THC irrespectively of the simultaneous presence
of CBD. The most performing carbon black typology used for such a purpose was chosen among various commercial
products tested on the basis of preliminary tests performed on 1,3-dihydroxybenzene, constituting the
redox active moiety of cannabinoids. The voltammetric responses collected in various solutions containing
different amount of THC and CBD were initially elaborated by Principal Component Analysis, assessing the
possibility of identifying samples with similar concentrations of THC irrespectively of the CBD concentration
values, and vice-versa. Afterwards a preliminary Partial Last Square regression was performed to evaluate the
possibility of a quantitative analysis of both THC and CBD. This approach suggests the possibility of using the
sensor proposed to screen samples containing THC even in the presence of high amounts of CBD
Development of an electrochemical sensor based on carbon black for the detection of cannabidiol in vegetable extracts
Full text linkA glassy carbon electrode chemically modified with a carbon black coating is proposed here for the rapid and portable determination of cannabidiol (CBD) in a commercial Cannabis seed oil and in fibre-type Cannabis sativa L. leaves. The mechanism of CBD oxidation was studied in relation to simpler phenyl derivatives bearing the same electroactive group, namely resorcinol and 2-methylresorcinol. These molecules also allowed us to determine the best conditions for the electrochemical detection of CBD, as to the pH value and to the best solvent mixture to use. Carbon black was chosen among nanostructured carbon-based materials owing to its outstanding features as an electrode modifier for analyte detection. The performance of the modified electrode was determined by flow injection analyses of standard solutions of CBD, obtaining a linear correlation between the oxidation current and the analyte concentration; the sensor response is characterised by suitable repeatability and reproducibility. The analysis of commercial products by the standard addition method allowed us to ascertain the accuracy of the sensor for the detection of CBD in real samples
An electrochemical approach for the prediction of Δ9-tetrahydrocannabinolic acid and total cannabinoid content in Cannabis sativa L
No full textTwo electrochemical sensors are proposed here for the first time for the fast screening of cannabinoids in Cannabis sativa L. plant material (inflorescences). The accurate control of cannabinoid content is important for discriminating between recreational, i.e. illegal, and fibre-type C. sativa samples, which differ mainly according to the amount of Δ9-tetrahydrocannabinol (Δ9-THC) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA). Two screen printed electrodes obtained using different electrode materials were tested for the analysis of extracts from recreational and fibre-type C. sativa and their performance was compared with a consolidated method based on high-performance liquid chromatography (HPLC). The voltammetric responses recorded in the different samples reflected the compositional differences of the recreational and fibre-type extracts in accordance with the results of HPLC analyses. Moreover, the quantification of Δ9-THCA and the total cannabinoid content on the basis of the intensity of the peaks of the voltammograms was possible through a simple and fast electrochemical procedure
On the feasibility of a portable electrochemical measuring system for the on-site measurement of cannabinoids
No full textGiven the neuroprotective, anti-inflammatory, and analgesic properties of cannabidiol (CBD), many countries have recently legalized the use of fiber-type Cannabis products, including those known as 'Cannabis light'. Nonetheless, in freely commercialized products, it is not uncommon to find Δ9-tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, in concentrations exceeding the legal limit. To determine whether a product is commercially viable, the THC/CBD ratio is typically analyzed using chromatographic techniques. However, chromatographic techniques have costs, complexity, and response times that prevent their in-situ use, making control actions much more expensive and ineffective. In this work, we report our preliminary activities aimed at verifying the possibility of performing in-situ analysis of cannabinoids in cannabis-derived products using an ad-hoc designed measuring system based on screen-printed electrodes modified with carbon black. The results obtained from preliminary tests comparing fiber cannabis (legal THC concentration) and recreational cannabis (illegal THC concentration) suggest that the proposed system can allow the effective and efficient in-situ analysis of cannabis-derived products
Voltammetric determination of hydrogen peroxide at high concentration level using a copper electrode
No full textThe determination of strong oxidizing species is of outmost importance in a number of practical applications. However, the currently available analytical tools should be improved in terms of reliability, automation, and costs. With this respect amperometric techniques are particularly promising candidates; nevertheless, the performance of conventional electrode materials, such as Au and Pt, are unsatisfactory, particularly in terms of resistance to fouling. In addition, electroanalytical methods and devices most commonly pay highest attention to the determination of similar analytes present in trace. On the other hand, the determination of high concentrations is of particular importance in industrial and environmental frames. Especially with reference to similar situations, the present paper reports the electrochemical behavior and analytical effectiveness of an alternative electrode material, namely Cu, in the presence of H2O2 at high concentrations (up to 0.5 M) and at different pH values. Furthermore, the behavior in real, harsh matrices, namely wastewater samples exhibiting different levels of chemical oxygen demand, is also reported. The results have been fruitfully employed in the development of an analytical procedure for the determination of H2O2 in similar matrices. A statistical treatment of the electrochemical responses suggests that the repeatability and reproducibility are well adequat
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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