1,721,023 research outputs found
Determination of Pesticides in Wheat Flour Using Microextraction on Packed Sorbent Coupled to Ultra-High Performance Liquid Chromatography and Tandem Mass Spectrometry
No full textAn ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) method for multiclass analysis of pesticide and fungicide residues in wheat flour based is presented. An efficient and rapid cleanup based on microextraction by packed sorbent (MEPS) has been developed in order to have a good enrichment factor together with a low matrix effect. The target analytes were 25 pesticides widely used in wheat, with different physico-chemical characteristics and different mechanism of action: acetylcholinesterase inhibitors such as organophosphorus, carbamates, neonicotinoids, and inhibitors of ergosterol such as imidazoles and triazoles. MEPS was shown to be successful with reduction of the amount of solvent required and possibility of automation of the cleanup procedure. The whole method was then validated according to the SANCO/12571/2013 guidelines, proving its suitability as confirmation method for the selected analytes
Press-transferred carbon black nanoparticles on board of microfluidic chips for rapid and sensitive amperometric determination of phenyl carbamate pesticides in environmental samples
No full textThe authors describe a strategy for rapid and sensitive determination of phenyl carbamate pesticides in environmental samples. It consists of the following steps: (a) Enrichment and clean-up of the analytes using a C18 microtip based procedure; (b) alkaline hydrolysis of the carbamates (carbofuran, isoprocarb and carbaryl) to form phenol derivatives; and (c) fast separation and amperometric detection in a microfluidic chip (MCs). The microchips were fabricated by using press-transferred carbon black nanoparticles (CB-NPs) as electrochemical sensing nanomaterial. The excellent electrochemical behavior of the CB-NPs coupled to the microchip warrants good separation and allows for the voltammetric determination (best at a working voltage of +0.70 V vs Ag/AgCl) of the carbamates within < 6 min. The authors also describe a rapid procedure for the clean-up and enrichment of the carbamates from real samples by using a C18 microtip. The procedure allowed a 10-fold enrichment of the analytes, and this led to a detection limits in ̴the 0.7 to 1.2 μM concentration range. The assay was applied to samples of river, lake and irrigation water that were spiked with carbamates at 50 and 100 μM levels. Recoveries are in the 87 to 108 % range, and RSDs (n = 3) in the 5 to 11 % range. The exploitation of the such nanomaterials coupled to microfluidics and microextraction procedures for real sample analysis in our preception represents a most viable tool for the analysis of complex real samples, for on-site environmental monitoring, and for rapid diagnosis. [Figure not available: see fulltext.
Press-Printed Conductive Carbon Black Nanoparticle Films for Molecular Detection at the Microscale
No full textCarbon black nanoparticle (CBNP) press-transferred film-based transducers for the molecular detection at the microscale level were proposed for the first time. Current-sensing atomic force microscopy (CS-AFM) revealed that the CBNP films were effectively press-transferred, retaining their good conductivity. A significant correlation between the morphology and the resistance was observed. The highest resistance was localized at the top of the press-transferred film protrusions, whereas low values are usually obtained at the deep crevices or grooves. The amount of press-transferred CBNPs is the key parameter to obtain films with improved conductivity, which is in good agreement with the electrochemical response. In addition, the conductivity of such optimum films was not only Ohmic; in fact, tunneling/hopping contributions were observed, as assessed by CS-AFM. The CBNP films acted as exclusive electrochemical transducers as evidenced by using two classes of molecules, that is, neurotransmitters and environmental organic contaminants. These results revealed the potential of these CBNP press-transferred films for providing new options in microfluidics and other related micro- and nanochemistry applications
Integrated 3D-Printed Microfluidic Device for Immunocapture and Electrochemical Assessment of Transferrin Saturation in Point-of-Care Stroke Diagnostics
No full text: A 3D-printed electrochemical microfluidic device (3D-EMD) was developed to assess the transferrin saturation (TSAT) biomarker in ischemic stroke patients. The all-in-one 3D-EMD integrates a strategically engineered immunoassay module for the direct and selective isolation of transferrin (Tf) from unpretreated clinical samples, unaffected by sample coloration, with an interchangeable electrochemical sensor for the simultaneous detection of Tf and Tf-bound iron. Both modules are interconnected through microfluidic channels whose flow is regulated by a cylindrical rotary valve. The analytical workflow enables magnetic bead-based direct Tf immunocapture and simultaneous electrochemical detection of Tf and Tf-bound iron via square wave voltammetry, allowing TSAT assessment within 60 min using only 50 μL of sample. Validation with certified reference materials demonstrated excellent accuracy (Er ≤ 5%) and precision (RSD ≤ 4%). Application to human serum from ischemic stroke patients showed strong correlation (r = 0.87) and agreement (slope 0.9 ± 0.3; intercept 6 ± 10; p < 0.05) with the urea-PAGE reference method, which typically requires up to 18 h. Overall, the 3D-EMD constitutes an elegant, fully integrated dual-functionality platform that seamlessly combines customizable sample preparation with online electrochemical detection in a single device. This configuration enables direct serum analysis and supports clinical decision-making in time-critical conditions. The device shows strong potential as a rapid point-of-care testing candidate for ischemic stroke and as a next-generation platform for broader clinical diagnostics
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
Press-transferred carbon black electrodes coupled to microchip electrophoresis for food pesticides detection
No full textIn this work the assembling of novel carbon black (CB) press-transferred electrodes (CB-PTEs) is reported. The press-transferred nanomaterial based - Approach presented may open new gates for electrochemical sensing since this technology does not require clean room facilities [1-2]. The electrodes have been designed to be coupled to microchip electrophoresis (ME) that gives excellent opportunities to carry out a quantitative multi-residual screening analysis characterized by rapidity, low sample and reagent consumption, and extremely low waste generation
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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