Selective spectrophotometric determination of iron in river waters using 4-(4-methyl-2-thiazolylazo)resorcinol

Abstract

Thiazolylazophenols react sensitively with iron(II) to form brown complexes, which show a characteristic absorption in the near-infrared region. These compounds possess a hydroxyl group in the o-position next to the azo group. Amongst them, the iron(II)- 4-(4-methyl-2-thiazolylazo)resorcinol complex has an absorption maximum at 735 nm. The absorbance is constant at pH 8.9–11.6 and Beer's law is obeyed for up to 2 p.p.m. of iron, with a molar absorptivity of 2.49 × 10⁴ l mol^–1 cm^–1. Many ionic species can be tolerated, especially transition metal ions of the 3d series. The method has been applied successfully to the analysis of river waters, coffee, green tea and synthetic mixtures containing transition metal ions.