Determinação de traços de maganes por espectrofotometria de absorção atomica apos pre-concentração seletiva em coluna contendo 1-(2-Piridilazo)-2-Naftol [PAN] absorvido em naftaleno microcristalino

AUTOR(ES)

Aparecida Pereira dos Anjos

DATA DE PUBLICAÇÃO

1992

RESUMO

The great diversity of methods concerning the determination of trace levels of manganese, in different matrices, demonstrates the importance of this element. One of the most common methods is that based on atomic absorption spectrophotometry, usually performed after a preconcentration step. Among several preconcentration techniques of trace metaIs, the adsorption of organic reagents onto solid supports has been frequently used. In these cases, the determination is performed after the metal elution by a suitable solvent. In this work, a new system for preconcentration of trace manganese is proposed. The system employs a 3% (w/w) 1-(2-Pyridylazo)-2-Naphthol (PAN), adsorved on microcrystalline naphthalene. 200 mg of this complexing mixture is placed in a glass column (15 cm x 0.4 cm i.d.) and conditioned with a NH4Cl/NH4OH buffer solution (pH = 9.5). The aqueous sample, containing manganese, is treated with sodium potassium tartrate solution, to avoid hydrolyses of other ions, then with hydroxylamine, to prevent the oxidation of Mn(II) to Mn(III) and finally with buffer solution at pH 9.5. Then this resulting solution is passed through the column where the Mn(II) is retained. The column is first washed with deionized water and then with 10,0 mL dymetilformamide to dissolve the Mn(II)-PAN/naphthalene complex. Finally the manganese is determined by air-acetilene flame atomic absorption spectrophotometry. About 1 mg of manganese can be concentrated from 200 mL of aqueous in samples, where its concentration is as low as 5 mg L. The accuracy was acertained using certified samples of urine and glass. Water samples of the Campinas region were analyzed and the results are in good agreement with those obtained by the graphite furnace atomic absorption spectrophotometry.

ASSUNTO(S)

quimica analitica manganes - eletrometalurgia

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