Extração e determinação simultanea por emissão em plasma de nutrientes e elementos toxicos em amostras de interesse agronomico

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

The objective of this study was to evaluate chemical elements extraction processes for soil, plant and residue analysis by inductively coupled plasma atomic emission spectrometry (ICP-AES) technique. The critical step of the chemical analysis using the ICP-AES technique, is the sample extraction or dissolution. In the case of soil analysis, boron was a troublesome micronutrient. Hot water is the most widely extractor used for boron extraction in soils for the diagnosis of the nutrient availability. This procedure is tedious and requires some especial cares. An alternative procedure was developed in this thesis using a domestic microwave oven and BaCI2 as extraction solution. Good correlation (r=0.960) was found between the extraction by boiling water and the proposed method, for 13 soils, using ICP-AES. The B contents determined by ICP-AES did not significantly differ from those obtained by spectrophotometric method (r=0.980). The microwave method is the official procedure for soils of the State of São Paulo (Brazil), since 1994. Plant digestion may be performed by dry ashing or wet digestion, using heating by conduction or microwave. Since results in the literature for sample digestion are, in general, not consistent, it was necessary to establish a proper routine for plant analysis and nutrient diagnosis. Four samples from International Plant-Analytical Exchange (IPE) program and one NIES (National Institute for Environmental Studies - Japan Environmental Agency) certified reference material were used and the elements AI, B, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S e Zn were analyzed by ICP-AES. The results obtained with the HNO3-HCIO4 digestion method presented higher variability for the element contents in the samples studied; Na and B showed the largest range of variation (148% and 325%, respectively). The dry ashing method presented relatively better results, except for Na (583%), B (236%) and S (54%). The results with the microwave digestion method were more consistent and reproducible for most elements, but this procedure requires special cares for routine analysis. The dry ashing was chosen for routine analysis in the Plant and Soil Laboratory of Instituto Agronômico, nevertheless the microwave method is used for special analysis, when more precision is required. Three procedures for the digestion of residues were compared; (1) open system using HNO3-HClO4 , (2) closed system in microwave oven using HNO3 (EPA-3051 method) and (3) closed system in microwave oven using aqua-regia. Urban domestic wastes, swine and dairy manure and NIES sediment certified reference material were used as samples. All extractions were analyzed for Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn by ICP-AES. Microwave digestion with aqua- regia extracted higher amounts of metals, with recoveries greater than 90% for Fe, Mn, Cu, Pb, Zn and Cd, 76% for Ni and 61 % for Cr. This procedure also presented higher amounts of Fe, Mn, Zn and Cr for the municipal waste compost, the sewage sludge and for the swine manure, when compared with other methods. The CETESB ("Companhia de Tecnologia de Saneamento Básico") legislation for the application of biologically treated sludge in agricultural areas was based in these studies.

ASSUNTO(S)

quimica vegetal plantas - analise solos - analise solos - amostragem

ACESSO AO ARTIGO

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