472 research outputs found

    Influenceof measuring conditions on the quantification of spectroscopic signals inTA-FTIR-MS systems

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    Simultaneous thermal analysis (TA) and evolved gas analysis by mass spectrometry (MS) and/or Fourier transform infrared spectroscopy (FTIR) is a powerful hyphenated technique combining direct measurement of mass loss and sensitive spectroscopic analysis. In the present study the influence of several experimental parameters which may affect the quantification of FTIR signals have been studied using a combined TA-FTIR-MS system. Parameters studied include: sample mass (1-400 mg), carrier gas flow rate (25-200 mL min-1), resolution of the FTIR spectrometer (1-32 cm-1), and location of injection of the calibrating gas. MS analysis, which was not significantly affected by the experimental conditions, was used as a reference for assessing the accuracy of quantification by FTIR. The quantification of the spectroscopic signals was verified by the decomposition (NaHCO3) or dehydration (CuSO4·5H2O) of compounds with well-known stoichiometry. The systematic study of the parametric sensitivity revealed that spectral resolution and carrier gas flow rate, which affect the acquisition time in the IR-cell, are key parameters that must be adjusted carefully for reliable quantification. The dependence of the reliability of quantification on these parameters is illustrated and conditions leading to proper quantification are discussed. As an example, for a standard spectral resolution of 4 cm-1 and a FTIR gas cell volume of 8.7 mL, the carrier gas flow must be lower than 100 mL min-1 for warranting accurate results (relative deviation <2%). The concentration range of analyzed species is limited but can be extended by proper selection of the wavenumber regions for molecules giving strong IR signal

    A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species

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    As espécies de Hemibrycon que ocorrem a leste das Cordilheiras dos Andes são revisadas com base na análise do material tipo e exemplares adicionais. Nove espécies são redescritas: H. beni da bacia do río Beni, Bolívia; H. helleri do alto río Ucayali, Peru; H. huambonicus para as bacias dos ríos Huallaga e Marañon, Peru; H. jeslkii para as porções superiores das bacias dos rios Marañon, Ucayali e Madeira, Bolívia, Brasil e Peru; H. metae para a bacia do río Orinoco, Colômbia e Venezuela, e bacias costeiras do Caribe na Venezuela; H. polyodon (espécie-tipo) para a bacia do río Pastaza, Equador; H. surinamensis para as bacia costeiras da Guiana Francesa e Suriname, e porção inferior das bacias dos rios Tapajós, Tocantins e Xingu, Brasil; H. taeniurus para os rios da ilha de Trinidad, Trinidad and Tobago; H. tridens para a bacia do alto río Ucayali, Peru. Duas espécies novas são descritas: H. inambari para a bacia do alto río Madre de Dios, Peru e H. mikrostiktos para a bacia do río Ucayali, Peru. Estas espécies distinguem-se principalmente pelo padrão de colorido e caracteres merísticos. A área de distribuição do gênero é ampliada para as porções inferiores das bacias do Tapajós, Tocantins e Xingu, Brasil, com o primeiro registro de H. surinamensis para este país. Uma nova diagnose e descrição são fornecidas para a espécie-tipo do gênero, apesar de ter sido recentemente redescrita. A série-tipo de H. helleri previamente considerada questionável é encontrada e descrita. Hemibrycon coxeyi e H. pautensis são considerados sinônimos juniores de H. polyodon. Tetragonopterus (Hemibrycon) trinitatis, anteriormente considerada como species inquirenda em Characidae, e Hemibrycon guppyi são sinônimos juniores de H. taeniurus. Hemibrycon orcesi é transferida para Boehlkea. É apresentada uma chave taxonômica para as espécies do gênero a leste das Cordilheiras dos Andes.The species of Hemibrycon occurring in the east of the Andean Cordilleras are reviewed based on their type series and additional specimens. Nine species are redescribed: H. beni from río Beni basin, Bolivia; H. helleri from the upper rio Ucayali, Peru; H. huambonicus from the ríos Huallaga and Marañon basins, Peru; H. jeslkii from the upper portions of ríos Marañon, Ucayali and Madeira basins, Bolivia, Brazil, and Peru; H. metae from río Orinoco basin, Colombia and Venezuela, and Caribbean coastal basins of Venezuela; H. polyodon (type species) from río Pastaza basin, Ecuador; H. surinamensis from coastal basins of French Guiana and Suriname, and from lower rios Tapajós, Tocantins and Xingu basins, Brazil; H. taeniurus from river basins from Trinidad Island, Trinidad and Tobago, and H. tridens from upper río Ucayali basin, Peru. Two new species are described: H. inambari from the upper río Madre de Dios basin, Peru and H. mikrostiktos from río Ucayali basin, Peru. These species are distinguished among themselves mainly by the color pattern, and meristic characters. The distribution area of the genus is enlarged reaching the lower Tapajós, Tocantins and Xingu river basins, Brazil, with the first record of the occurrence of H. surinamensis in this country. A new description and diagnosis is provided for the type species of the genus, regardless its recent redescription. The type series of H. helleri that was previously considered dubious is found and described. Hemibrycon coxeyi and H. pautensis are considered junior synonyms of H. polyodon. Tetragonopterus (Hemibrycon) trinitatis, previously considered species inquirenda in Characidae, and Hemibrycon guppyi are junior synonyms of H. taeniurus. Hemibrycon orcesi is transferred to Boehlkea. A taxonomic key for the species of the genus to the east of the Andean Cordilleras is presented
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