Full text
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| Author(s): |
Marco Rogério Barrios
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 1999-08-18 |
| Examining board members: |
Arthur Pinto Chaves;
Alcídio Abrão;
Patricia Helena Lara dos Santos Matai
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| Advisor: | Arthur Pinto Chaves |
| Abstract | |
This text describes the development of carbono paste electrodes modified by Es-346 (poli-amidoxime) resin for the potenciometric determination of gallium in alcaline médium, pH = 11,0. Through a systematic study it was possible to establish that best compositions for the carbono paste (% of grafite : resin : mineral oil) have been 50% : 25% and 40% : 35% : 25%. Electrodes containing 25 and 35% of resin have shown the same reproducibility, but in the former case the determination limit was three times higher. The best previous conditioning times for these electrodes in gallium solution have been 15 and 10 minutes. Potenciometric tests have shown that there are two mechanisms for these sensors: below 4,0X10-4 mol.L-1 the potencial in the cell varied linearly with the gallium concentration in solution. Above this value the potential varies with the log of the concentrations. In this last case the slope of analytical curve was 40 mV/decade in Ga(III) concentration, showing that the electrode response was due the [Ga(OH)2]+ (sub nernstian response) or [Ga(OH)2]+ (super nernstian response. (AU) | |