Titrimetric method for phosphite determination in agricultural chemical samples

Quimica nova

Gomes Neto, José Anchieta¹  Franzini, Vanessa Pezza¹ 

[1] Universidade Estadual Paulista, Araraquara, Brasil

关键词: phosphite;    titrimetry;    iodine.;   

DOI  :  10.1590/S0100-40422007000200013

学科分类：化学（综合）

来源: Sociedade Brasileira de Quimica

【 摘 要 】

A new titrimetricmethod for the determination of phosphite in fertilizer samples, based on reactionof H3PO3 with standard iodine solution in neutral media,is proposed. Diluted samples containing ca. 0.4% m/v P2O5are heated and titrated with 0.05 mol L-1 iodine standard until thesolution becomes faint yellow. Back titration is also feasible: a slight excessof titrant is added followed by starch indicator and titration is completedtaking as the end point the change in color from blue to colorless. The influenceof chemical composition and pH of buffers, temperature and foreign species onwaiting time and end-point detection were investigated. For the Na2HPO4/NaH2PO4buffer (pH 6.8) at 70 °C, the titration time was 10 min, corresponding toabout 127 mg iodine, 200 mg KI and 174 mg Na2HPO4 and176 mg NaH2PO4 consumed per determination. Accuracy waschecked for phosphite determination in seven fertilizer samples. Results obtainedby the proposed procedure were in agreement with those obtained by spectrophotometryat 95% confidence level. The R.S.D. (n=10) for direct and back titrationwas 0.4% and 1.3% respectively.

【 授权许可】

CC BY