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Master's Dissertation
DOI
10.11606/D.46.1994.tde-06112009-141955
Document
Author
Full name
Simone Jaconetti Ydi
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1994
Supervisor
Committee
Tokoro, Roberto (President)
Baccan, Nivaldo
Oliveira, Elisabeth de
Title in Portuguese
Determinação espectrofotométrica de cobalto na presença de zinco, manganês e níquel
Keywords in Portuguese
Complexo de cobalto (II)-bipiridina
Determinação espectrofotométrica de cobalto
Estabilização de boro-hidreto
Química analítica
Química analítica instrumental
Abstract in Portuguese
O ion Co2+, quando coordenado com ligante bipiridina (bipy), pode ser reduzido por ataque químico de redutores fortes, como NaBH4 (boroidreto de sódio), formando [Co(I) (bipy)3]+, azul. Este complexo pode ser determinado espectrofotometricamente por conferir um espectro na região do visível com λmax = 600 nm (ε = 5,8x103 L.mol-1 .cm-1). Somente cobalto estabiliza-se na forma de [M(i)(bipy)3]+, enquanto que outros metais como Mn, Ni e Zn reduzem-se ao estado metálico. A estabilização do NaBH4 foi conseguida em DMF (N,N´-dimetilformamida). Foi utilizado o método da adição de padrão, condicionando-se o sistema ao meio H20:DMF na proporção de 2:1 (v/v) , T = 25°C, excesso de ligante e excesso de 240 vezes de NaBH4. Níquel interfere acima de 2,5x10-5 mol.L-1 , manganês acima de 5,0x10-5 mol.L-1 e zinco acima de 1,0x10-4 mol.L-1, quando CCO2+ = 5,0x10-5 mol.L-1. Este procedimento foi realizado em amostra NBS167, encontrando-se valores 1% menores que o valor certificado.
Title in English
Spectrophotometric determination of cobalt in the presence of nickel, manganese and zinc
Keywords in English
Analytical chemistry
Bipyridine-cobalt (II) complex
Boronhydride stabilization
Spectrophotometric determination of cobalt
Abstract in English
The cobalt (II) ion complexed with bipyridine (bipy) can be reduced chemically by reductant like sodium boronhydride yelding blue [Co(I)(bipy) 3]+. This complex can be determined spectrophotometrically using visible spectra at λ = 600 nm (ε = 5,8x103 L.mol-1 . cm-1). When Mn, Ni and Zn are present togheter with cobalt (II) and the mixture is complexed by bipyridine and furtherly treated by boronhydride, the ions of niekel, manganese and zinc are reduced to fundamental state remaining [Co(I)(bipy)3]+ soluble complex. The stabilization of NaBH4 was achieved in N,N'-dimetilformamide (DMF). Interference studies showed for [Co2+] = 5,0x10-5 mol.L-1, 2:1 of H20:DMF, t = 25°C, excess presence of bipyridine ligand and 240 times excess of NaBH4 : nickel start interfere at 2,5x10-5 mol.L-1, manganese at 5,0x10-5 mol.L-1 and zinc at 1,0x10-4 mol.L-1. The procedure was apllied at a cobalt alloy NBS167 using standard addition method and the recovery was 1% less than certificated value.
 
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Publishing Date
2009-11-10
 
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