Reversed-phase liquid chromatographic simultaneous determination of iron(III) and iron(II) as complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol: Determination of iron(III) and iron(II) in water samples and ultrasound field effect on distributio

The formation of Fe(III) and Fe(II) chelates with pyridylazo and thiazolylazo reagents was examined. Optimum conditions for the formation of Fe(III) and Fe(II) chelates with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) were in detail evaluated. The LC method for simultaneous separation of Fe(III) and Fe(II) ions as 5-Br-PADAP chelates was evaluated using the PEEK column with C18 e.c. stationary phase and acetonitrile+water (90:10, v/v) eluent containing the 1×10−3 mol l−1 C12H25SO3Na, the ion-pairing reagent, pH 3.4–3.6. The simultaneous determination of 20–500 μg l−1 Fe(II) ions (detection at 555 nm) and 20–500 μg l−1 Fe(III) ions (detection at 585 nm) as 5-Br-PADAP chelates (for both ions, detection limit, 18 μg l−1 for 20 μl loop) was established. The chromatographic method was applied to the water analysis. Although the present method is able to determine both Fe(III) and Fe(II) ions, the Fe(III) ion was not detected in all water samples. The Fe(II) was detected only in fresh gathered oligocene water at the level of 135 μg l−1. The present method was used to the investigation of the distribution of Fe(III)/Fe(II) ions in aqueous and micellar solutions after action of external, ultrasonic field.