1,720,966 research outputs found
Poly(methyloctylsiloxane) Immobilized On Silica As A Sorbent For Solid-phase Extraction Of Some Pesticides
No full textA laboratory-made sorbent for solid-phase extraction (SPE) was obtained by thermal immobilization of poly(methyloctylsiloxane) (PMOS) onto silica. Cartridges packed with the new sorbent were used for the simultaneous determination of imazethapyr, nicosulfuron, diuron, linuron and chlorimuron-ethyl in water. These pesticides were separated and quantified using high-performance liquid chromatography with diode array detection (HPLC-DAD). The recoveries achieved with the laboratory-made PMOS cartridges were compared with those of some commercially available silica-based and polymer-based cartridges having C18, C8 and NH2 pendant groups. Method validation using the laboratory-made sorbent was performed for the five pesticides at three fortifications levels (1×, 2× and 10× the limit of quantification of each pesticide). The laboratory-made PMOS cartridge has low cost preparation and showed good recoveries (72-111%) for all pesticides. Repeatability and intermediate precision were lower than 15%. Its performance was similar or even better, in some cases, than those of the commercial cartridges. © 2006 Elsevier B.V. All rights reserved.11142211215Zhu, Q., Degelmann, P., Niessner, R., Knopp, D., (2002) Environ. Sci. Technol., 36, p. 5411Majors, R.E., (2003) LC-GC Eur., 16, p. 2Maurer, H.H., (2000) Comb. Chem. High Throughput Screen, 3, p. 467Moors, M., Massart, D.L., McDowall, R.D., (1994) Pure Appl. Chem., 66, p. 277Jardim, I.C.S.F., Collins, K.E., Collins, C.H., (2004) Microchem. J., 77, p. 191Jardim, I.C.S.F., Anazawa, T.A., (1994) J. Liq. Chromatogr., 17, p. 1265Jardim, I.C.S.F., Collins, K.E., Anazawa, T.A., (1999) J. Chromatogr. A, 849, p. 299Tonhi, E., Collins, K.E., Collins, C.H., (2002) J. Chromatogr. A, 948, p. 109Bottoli, C.B.G., Collins, K.E., Collins, C.H., (2003) J. Chromatogr. A, 987, p. 87Lopes, N.P., Collins, K.E., Jardim, I.C.S.F., (2003) J. Chromatogr. A, 987, p. 77Collins, K.E., Bottoli, C.B.G., Vigna, C.R.M., Bachmann, S., Albert, K., Collins, C.H., (2004) J. Chromatogr. A, 1029, p. 43Bottoli, C.B.G., Vigna, C.R.M., Fischer, G., Albert, K., Collins, K.E., Collins, C.H., (2004) J. Chromatogr. A, 1030, p. 17Morais, L.S.R., Jardim, I.C.S.F., (2005) J. Chromatogr. A, 1073, p. 127Queiroz, S.C.N., Melo, L.F.C., Jardim, I.C.S.F., (2002) J. Chromatogr. A, 948, p. 171Pozzebon, J.M., Queiroz, S.C.N., Melo, L.F.C., Kapor, M.A., Jardim, I.C.S.F., (2003) J. Chromatogr. A, 987, p. 381Melo, L.F.C., Collins, C.H., Jardim, I.C.S.F., (2004) J. Chromatogr. A, 1032, p. 51Melo, L.F.C., Collins, C.H., Jardim, I.C.S.F., (2005) J. Chromatogr. A, 1073, p. 75Ribani, M., Bottoli, C.B.G., Collins, C.H., Jardim, I.C.S.F., Melo, L.F.C., (2004) Quím. Nova, 27, p. 771Tolosa, I., Readman, J.W., Mee, L.D., (1996) J. Chromatogr. A, 725, p. 93Brouwer, E.R., Struys, E.A., Vreuls, J.J., Brinkman, U.A.Th., (1994) Fresenius J. Anal. Chem., 350, p. 487Slobodník, J., Louter, A.J.H., Vreuls, J.J., Liska, I., Brinkman, U.A.Th., (1997) J. Chromatogr. A, 768, p. 23
Preparation Of Stationary Phases For Reversed-phase High-performance Liquid Chromatography Using Thermal Treatments At High Temperature
No full textBatches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 °C for 24 h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4 h at higher temperatures (150-400 °C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, 29Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 °C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 °C and an increase in the resolution of the components, mainly for the phase heated at 300 °C. Such results demonstrate that a two-step thermal treatment (100 °C then 150-300 °C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography. © 2007 Elsevier B.V. All rights reserved.11561-2 SPEC. ISS.6067Schomburg, G., (1991) Trends Anal. Chem., 10, p. 163Petro, M., Berek, D., (1993) Chromatographia, 37, p. 549Jardim, I.C.S.F., Collins, K.E., Collins, C.H., (2004) Microchem. J., 77, p. 191Anazawa, T.A., Jardim, I.C.S.F., (1994) J. Liq. Chromatogr., 17, p. 1265Collins, K.E., Granja, M.L.M.M., Pereira, R.G., Anazawa, T.A., Jardim, I.C.S.F., (1997) Chromatographia, 45, p. 99Mano, E.B., Mendes, L.C., (1999) Introdução a Polímeros. second revised ed., , Edgard Blücher, São PauloPetsev, N.D., Perov, G.I., Alexandrova, M.D., (1985) Chi. Dimitov, Chromatographia, 20, p. 228Gawdizik, J., (1991) Chromatographia, 31, p. 258Bemgard, A., Blomberg, L.G., (1987) J. Chromatogr., 395, p. 125Chuang, C.H., Shanfield, H., Zlatkis, A., (1987) Chromatographia, 23, p. 169Markides, K., Blomberg, L., Buijten, J., Wännman, T., (1983) J. Chromatogr., 267, p. 29Schomburg, G., Köhler, J., Figge, H., Deege, A., Bien-Vogelsang, U., (1984) Chromatographia, 18, p. 265Jardim, I.C.S.F., Collins, K.E., Anazawa, T.A., (1999) J. Chromatogr. A, 849, p. 299Bottoli, C.B.G., Vigna, C.R.M., Fischer, G., Albert, K., Collins, K.E., Collins, C.H., (2004) J. Chromatogr., 1030, p. 217Bottoli, C.B.G., Collins, K.E., Collins, C.H., (2003) J. Chromatogr. A, 987, p. 87Collins, K.E., Bottoli, C.B.G., Vigna, C.R.M., Bachmann, S., Albert, K., Collins, C.H., (2004) J. Chromatogr. A, 1029, p. 43Morais, L.S.R., Jardim, I.C.S.F., (2005) J. Chromatogr. A, 1073, p. 127Lopes, N.P., Collins, K.E., Jardim, I.C.S.F., (2003) J. Chromatogr. A, 987, p. 77Tonhi, E., Collins, K.E., Collins, C.H., (2005) J. Chromatogr. A, 1075, p. 87Faria, A.M., Collins, K.E., Collins, C.H., (2006) J. Chromatogr. A, 1122, p. 114Pozzebon, J.M., Queiroz, S.C.N., Melo, L.F.C., Kapor, M.A., Jardim, I.C.S.F., (2003) J. Chromatogr. A, 987, p. 381Ohmacht, R., Kele, M., Matus, Z., (1989) Chromatographia, 28, p. 19Collins, K.E., Sá, A.L.A., Bottoli, C.B.G., Collins, C.H., (2001) Chromatographia, 53, p. 661Bottoli, C.B.G., Chaudhry, Z.F., Fonseca, D.A., Collins, K.E., Collins, C.H., (2002) J. Chromatogr. A, 948, p. 121Collins, K.E., Franchon, A.C., Jardim, I.C.S.F., Radovanovic, E., Gonçalves, M.C., (2000) LC-GC, 18, p. 106Bachmann, S., Melo, L.F.C., Silva, R.B., Anazawa, T.A., Jardim, I.C.S.F., Collins, K.E., Collins, C.H., Albert, K., (2001) Chem. Mater., 13, p. 1874Snyder, L.R., Kirkland, J.J., (1979) Introduction to Modern Liquid Chromatography. second ed., , Wiley, New YorkLopes, N.P., Collins, K.E., Jardim, I.C.S.F., (2004) J. Chromatogr. A, 1030, p. 225Nawrocki, J., (1991) Chromatographia, 31, p. 177Kirkland, J.J., Boyes, B.E., DeStefano, J.J., (1994) Am. Lab., 26, p. 3
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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