Journal of the Brazilian Chemical Society

URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/13322

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2003 - 20072

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Data final: 2009Assunto: search.filters.subject.Solos e nutrição do cafeeiro

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Agora exibindo 1 - 2 de 2
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    Comparative studies of the sample decomposition of green and roasted coffee for determination of nutrients and data exploratory analysis
    (Sociedade Brasileira de Química, 2007) Amorim Filho, Volnei R.; Politoa, Wagner L.; Gomes Neto, José A.
    The contents of some nutrients in 35 Brazilian green and roasted coffee samples were determined by flame atomic absorption spectrometry (Ca, Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K) and Kjeldahl (N) after preparing the samples by wet digestion procedures using i) a digester heating block and ii) a conventional microwave oven system with pressure and temperature control. The accuracy of the procedures was checked using three standard reference materials (National Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM 1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of data after application of t-test showed that results obtained by microwave-assisted digestion were more accurate than those obtained by block digester at 95% confidence level. Additionally to better accuracy, Other favorable characteristics found were lower analytical blanks, lower reagent consumption, and shorter digestion time. Exploratory analysis of results using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal elements to discriminate between green and roasted coffee samples.
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    Boron isotope dilution in cellular ractions of coffee leaves evaluated by inductively coupled plasma mass spectrometry with direct injection nebulization (DIN-ICP-MS)
    (Sociedade Brasileira de Química, 2003) Bellato, Ana Cláudia S.; Menegário, Amauri A.; Giné, Maria Fernanda
    Enriched 10B (94.14 atom %) was supplied to coffee plantlets for three months. Then boron isotope ratios were determined in the leaf cell compartments, cell wall, nuclei and chloroplast, after a sub-cellular fractionation procedure. The isotopic measurements were performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) provided with a direct injection nebulizer (DIN), introducing a sample volume of 50 µL. Isotopic ratios from 1.002 to 1.326 were determined with precision characterized by RSD lower than 1.5% for the enriched cell fractions with B concentrations ranging from 3.3 to 10.8 µg g-1. The detection limit (3σ) was 0.5 ng B mL-1. The average enrichments in 10B atom % found in the cell walls, nuclei and chloroplasts were 46.7, 44.5 and 48.8, respectively.