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Search Results: 1 - 10 of 117 matches for " Celio;Rohwedder "
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Flow system for pre-concentration and spectrophotometric determination of reactive mercury
Yonehara, Fernando S.;Pasquini, Celio;Rohwedder, Jarbas J. R.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000600007
Abstract: a new flow system to pre-concentrate and determine reactive mercury in effluents by photometry is presented. the system is based on the reduction of the reactive mercury present in a 500 ml sample with a sn(ii) solution. the reduced mercury is swept out by an argon stream and carried to a straight glass tube (60 cm long, 3 mm i.d.) inclined in an angle of 15o. the inner surface of this tube has been previously covered by a renewable liquid layer of an oxidant solution containing h2o2 (12%, m/v) and hno3 (3.0 mol l-1) produced after introduction and passage of a liquid monosegment containing those reagents. the swept hg0 undergoes an oxidative process and the hg(ii) formed is retained in the layer. after a 10 min sweep time interval the argon flow is stopped and a reagent monosegment (350 μl) containing par [4-(2-pyridylazo)resorcinol], 1.0 x 10-3 mol l-1, in an ammonia/ ammonium chloride buffer (4.0 mol l-1; ph 9.0) is introduced and passes through the glass tube. a strongly coloured complex between par and hg(ii) is formed and carried to the detection system composed of a light emitting diode (led, lmax = 525 nm) and a photodiode detector. sample processing time is about 12 min. the system is washed and a fresh liquid layer is formed, preparing the system for a new determination. this method concentrates the sample by a factor of 148 and achieves a detection limit of 0.16 μg l-1.
Gran method for end point anticipation in monosegmented flow titration
Aquino Emerson V,Pasquini Celio,Rohwedder Jarbas J. R,Raimundo Jr Ivo M
Journal of the Brazilian Chemical Society , 2004,
Abstract: An automatic potentiometric monosegmented flow titration procedure based on Gran linearisation approach has been developed. The controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. Alternatively, the end point can be determined by the second derivative procedure. In this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. The performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. The system employs a tubular Ag2S/AgCl indicator electrode. A typical titration, performed according to the IUPAC definition, requires only 60 mL of sample and about the same volume of titrant (AgNO3) solution. A complete titration can be carried out in 1 - 5 min. The accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the Gran and 1% and 0.5% for the Gran/derivative end point determination procedures, respectively. The proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.
Design and development of a multichannel potentiometer for monitoring an electrode array and its application in flow analysis
Jarbas J. R. Rohwedder,Celio Pasquini,Ivo M. Raimundo, Jr.,M. Concei ao,B. S. M. Montenegro,Alberto N. Araújo,Cristina M. C. M. Couto
Journal of Analytical Methods in Chemistry , 2002, DOI: 10.1155/s1463924602000147
Abstract: A versatile potentiometer that works with electrode arrays in flow injection and/or monosegmented flow systems is described. The potentiometer is controlled by a microcomputer that allows individual, sequential multiplexed or random accesses to eight electrodes while employing only one reference electrode. The instrument was demonstrated by monitoring an array of seven flow-through ion-selective electrodes for Ag
Gran method for end point anticipation in monosegmented flow titration
Aquino, Emerson V;Pasquini, Celio;Rohwedder, Jarbas J. R;Raimundo Jr, Ivo M;Montenegro, M. Concei??o B. S. M;Araújo, Alberto N;
Journal of the Brazilian Chemical Society , 2004, DOI: 10.1590/S0103-50532004000100017
Abstract: an automatic potentiometric monosegmented flow titration procedure based on gran linearisation approach has been developed. the controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. alternatively, the end point can be determined by the second derivative procedure. in this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. the performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. the system employs a tubular ag2s/agcl indicator electrode. a typical titration, performed according to the iupac definition, requires only 60 ml of sample and about the same volume of titrant (agno3) solution. a complete titration can be carried out in 1 - 5 min. the accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the gran and 1% and 0.5% for the gran/derivative end point determination procedures, respectively. the proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.
Near Infrared Spectroscopy: fundamentals, practical aspects and analytical applications
Pasquini, Celio;
Journal of the Brazilian Chemical Society , 2003, DOI: 10.1590/S0103-50532003000200006
Abstract: this paper intends to review the basic theory of near infrared (nir) spectroscopy and its applications in the field of analytical science. it is addressed to the reader who does not have a profound knowledge of vibrational spectroscopy but wants to be introduced to the analytical potentialities of this fascinating technique and, at same time, be conscious of its limitations. essential theory background, an outline of modern instrument design, practical aspects, and applications in a number of different fields are presented. this work does not intend to supply an intensive bibliography but refers to the most recent, significant and representative material found in the technical literature. because this paper has been produced as consequence of the first workshop on near infrared spectroscopy, whose venue was campinas - brazil, as a pre-conference activity of the xi national meeting on analytical chemistry (enqa), it also depicts the state of the art of nir spectroscopy in brazil, pointing out the current achievements and the need to take the technology to a level consistent with this country's economical activities.
Cues to the usefulness of grooming behavior in the evaluation of anxiety in the elevated plus-maze
Estanislau, Celio;
Psychology & Neuroscience , 2012, DOI: 10.3922/j.psns.2012.1.14
Abstract: grooming behavior has been reported to be a response to novelty and other stressors. however, studies that sought to identify anxiety-related measures in the elevated plus-maze have not found grooming as a reliable index. grooming has been implied with dearousal after a stressful experience. in the present work, a detailed investigation of this behavior was performed in a test with a longer duration (i.e., 10 min) than the usual duration in the elevated plus-maze. the level of anxiety was manipulated prior to the test by confining male rats to environments known to differ in the degree of aversive stimulation, including a familiar cage, a closed arm of the elevated plus-maze, and an open arm (i.e., the most aversive arm) of the elevated plus-maze. grooming behavior was classified into three constituent elements: rostral grooming, head grooming, and body grooming. the groups were compared with regard to conventional measures of the elevated plus-maze and grooming behavior. prior confinement to an open arm led to a delayed effect of decreased open-arm exploration undetectable during the first half of the test compared with rats previously confined to a closed arm. prior confinement to an open arm also increased the total duration of grooming during the second half of the test. these increases were found to be partially attributable to increases in the rostral element of grooming. the percentage of interrupted bouts was also found to discriminate the group previously confined to an open arm. these results indicate that prolongation of the session can reveal effects that are otherwise undetectable and that under such conditions some grooming measures can be useful in the evaluation of anxiety-like behavior.
Cues to the usefulness of grooming behavior in the evaluation of anxiety in the elevated plus-maze
Celio Estanislau
Psychology & Neuroscience , 2012,
Abstract: Grooming behavior has been reported to be a response to novelty and other stressors. However, studies that sought to identify anxiety-related measures in the elevated plus-maze have not found grooming as a reliable index. Grooming has been implied with dearousal after a stressful experience. In the present work, a detailed investigation of this behavior was performed in a test with a longer duration (i.e., 10 min) than the usual duration in the elevated plus-maze. The level of anxiety was manipulated prior to the test by confining male rats to environments known to differ in the degree of aversive stimulation, including a familiar cage, a closed arm of the elevated plus-maze, and an open arm (i.e., the most aversive arm) of the elevated plus-maze. Grooming behavior was classified into three constituent elements: rostral grooming, head grooming, and body grooming. The groups were compared with regard to conventional measures of the elevated plus-maze and grooming behavior. Prior confinement to an open arm led to a delayed effect of decreased open-arm exploration undetectable during the first half of the test compared with rats previously confined to a closed arm. Prior confinement to an open arm also increased the total duration of grooming during the second half of the test. These increases were found to be partially attributable to increases in the rostral element of grooming. The percentage of interrupted bouts was also found to discriminate the group previously confined to an open arm. These results indicate that prolongation of the session can reveal effects that are otherwise undetectable and that under such conditions some grooming measures can be useful in the evaluation of anxiety-like behavior.
Why it is called monosegmented flow analysis
Pasquini Celio
Journal of the Brazilian Chemical Society , 1999,
Abstract:
Near Infrared Spectroscopy: fundamentals, practical aspects and analytical applications
Pasquini Celio
Journal of the Brazilian Chemical Society , 2003,
Abstract: This paper intends to review the basic theory of Near Infrared (NIR) Spectroscopy and its applications in the field of Analytical Science. It is addressed to the reader who does not have a profound knowledge of vibrational spectroscopy but wants to be introduced to the analytical potentialities of this fascinating technique and, at same time, be conscious of its limitations. Essential theory background, an outline of modern instrument design, practical aspects, and applications in a number of different fields are presented. This work does not intend to supply an intensive bibliography but refers to the most recent, significant and representative material found in the technical literature. Because this paper has been produced as consequence of the First Workshop on Near Infrared Spectroscopy, whose venue was Campinas - Brazil, as a pre-conference activity of the XI National Meeting on Analytical Chemistry (ENQA), it also depicts the state of the art of NIR spectroscopy in Brazil, pointing out the current achievements and the need to take the technology to a level consistent with this country's economical activities.
Criar para o tempo, tempo para o criar, para criar o tempo: uma revisita??o da (ex) temporalidade na Recherche proustiana
Freire, José Celio;
Estudos de Psicologia (Natal) , 2001, DOI: 10.1590/S1413-294X2001000100009
Abstract: this work treats the relation between temporality and creation in marcel proust's masterpiece ? a la recherche du temps perdu ? and intends the discussion of the extemporality as dimension of the existence and of the process of subjectivation.
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