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Please use this identifier to cite or link to this item: http://acervodigital.unesp.br/handle/11449/25907
Title: 
Método titrimétrico para determinar fosfito em amostras agroindustriais
Other Titles: 
Titrimetric method for phosphite determination in agricultural chemical samples
Author(s): 
Institution: 
Universidade Estadual Paulista (UNESP)
ISSN: 
0100-4042
Sponsorship: 
  • Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Abstract: 
A new titrimetric method for the determination of phosphite in fertilizer samples, based on reaction of H3PO3 with standard iodine solution in neutral media, is proposed. Diluted samples containing ca. 0.4% m/v P2O5 are heated and titrated with 0.05 mol L-1 iodine standard until the solution becomes faint yellow. Back titration is also feasible: a slight excess of titrant is added followed by starch indicator and titration is completed taking as the end point the change in color from blue to colorless. The influence of chemical composition and pH of buffers, temperature and foreign species on waiting time and end-point detection were investigated. For the Na2HPO4/NaH2PO4 buffer (pH 6.8) at 70 °C, the titration time was 10 min, corresponding to about 127 mg iodine, 200 mg KI and 174 mg Na2HPO4 and 176 mg NaH2PO4 consumed per determination. Accuracy was checked for phosphite determination in seven fertilizer samples. Results obtained by the proposed procedure were in agreement with those obtained by spectrophotometry at 95% confidence level. The R.S.D. (n=10) for direct and back titration was 0.4% and 1.3% respectively.
Issue Date: 
1-Apr-2007
Citation: 
Química Nova. Sociedade Brasileira de Química, v. 30, n. 2, p. 308-311, 2007.
Time Duration: 
308-311
Publisher: 
Sociedade Brasileira de Química
Keywords: 
  • phosphite
  • titrimetry
  • iodine
Source: 
http://dx.doi.org/10.1590/S0100-40422007000200013
URI: 
Access Rights: 
Acesso aberto
Type: 
outro
Source:
http://repositorio.unesp.br/handle/11449/25907
Appears in Collections:Artigos, TCCs, Teses e Dissertações da Unesp

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