Dear Stefano,

One major interference using tetrabromophenolphthalein ethyl ester (TBPE) in the determination of nonionic surfactants in wastewater is the presence of Fe(II) which is known to be sensitive to this method (Tsurubou & Sakai, 1984).

Hoping this will be helpful,

Rafik

Thank you for your kind reply. I am looking for the paper you suggested, but I can not find it. Can you give me the complete reference?

Dear Stefano,

I do not have the full paper but you can get it from your library:

Paper High-sensitivity extraction-spectrophotometric determination of iron with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine and tetrabromophenolphthalein ethyl ester

Shigekazu Tsurubou and Tadao Sakai

Analyst, 1984,109, 1397-1399

DOI: 10.1039/AN9840901397

A sensitive extraction-spectrophotometric method for the determination of iron has been developed. Iron(II) forms a complex cation with 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) in aqueous solution and may be extracted into 1,2-dichloroethane (DCE) with tetrabromophenolphthalein ethyl ester (TBPE) as an ion pair at pH 5–7.5. The maximum absorbance of the extracted species occurs at 610 nm. The calibration graph is rectilinear over the range 0–0.25 p.p.m. of iron(II) and the apparent molar absorptivity of the ion-association complex is 1.9 × 105 l mol–1 cm–1. The extracted species has a molar ratio of Fe(II): PDT : TBPE = 1:3:2. The method has been applied to the determination of iron in various sera and also to river and well waters.

Rafik

thank you

stefano