Spectrophotometric determination of iron(II) after adsorption of its 2,2'-dipyridyl complex with tetraphenylborate ion on microcrystalline naphthalene.

A procedure is described for the spectrophotometric determination of iron(II) after adsorption of its 2, 2'-dipyridyl complex with tetraphenylborate on microcrystalline naphthalene. In the pH range 2.2-6.6, iron(II) forms a water-insoluble stable ion-pair in the presence of 2, 2'-dipyridyl and tetraphenylborate. The ion-pair is easily adsorbed on microcrystalline naphthalene by vigorous shaking for a few seconds. The adsorbed mixture is separated from aqueous solution, dried, dissolved in acetonitrile and the absorbance of the solution is measured at 521 nm. The effects of various factors such as pH, amounts of 2, 2'-dipyridyl and tetraphenylborate, shaking time, and diverse ions were studied. The method has been applied to the determination of iron(II) in standard material, metallic alloy and metal salt samples. The results were compared with the those of conventional 1, 10-phenanthroline colorimetric method.