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

Abstract

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.