Visual colorimetry of iron(II)-1,10-phenanthroline after preconcentration onto polyurethane foam.

Abstract

A simple solid-phase colorimetry using polyurethane foam (PUF) for the determination of iron(II) has been proposed. The 1,10-phenanthroline (phen) method is selective and sensitive, and is widely used for the determination of Fe(II) in aqueous solution. It is worthwhile to develop this method, which is suitable for visual colorimetry. An iron(II)-phen complex and its ion-associates, such as Br−, SCN− and ClO4−, were not extracted onto PUF at all. In the presence of sodium dodecyl sulfate (SDS), we found iron(II)-phen complex was adsorbed onto PUF and the iron concentration was visually measured from the resulting color onto PUF. The recommended procedure is as follows. Five ml of a 1 M acetate buffer solution (pH 4.7), 1 ml of 10 w/v% ascorbic acid, 3 ml of 0.1 w/v% phen, and 4 ml of 5×10−3 M SDS were added to a 200 ml sample solution containing less than 200 ppb of Fe(II). A chip of PUF (2×2×2 cm) was put into the solution and stirred with a magnetic stirrer for 20 minutes. The chip taken up from the solution was rinsed with distilled water and squeezed to remove any water. The color intensity of the PUF was then visually compared by a standard series method.