Extractive-spectrophotometric determination of manganese(II) using 3-bromobenzohydroxamic acid as chelating agent

Summary A new extractive spectrophotometric method is described for determining trace amounts of Mn(II) based on its reaction at pH 10.2 with 3-bromobenzohydroxamic acid (3BrHA) and subsequent extraction into Adogen 464 in toluene. The apparent molar absorptivity of the 1:3:1 (Mn:3BrHA:Adogen 464) complex is 8.7×10³ l·mol⁻¹ cm⁻¹ at 450 nm. Beer's law is obeyed from 0.5 to 6.0 mg·1⁻¹ of Mn(II) in the aqueous phase with a C.V. of 1.2%. The detection limit is 0.18 mg·1⁻¹. The method has been successfully applied to the determination of manganese in standard steel samples, natural water samples and plant material.