Spectrophotometric determination of traces of iron using a poly(vinyl chloride) membrane containing bathophenanthroline

Abstract

A sensitive and simple spectrophotometric method for the determination of traces of iron using a poly(vinyl chloride) (PVC) membrane containing 4,7-diphenyl-1,10-phenanthroline (bathophenanthroline) and o-nitrophenyl octyl ether ( o-NPOE) was developed. To a 5-ml water sample containing iron, 0.5 ml of 6.5 × 10 −2 M hydroxylammonium sulphate, 1.3 × 10 −2 M potassium iodide, and acetic acid-sodium acetate buffer solution (pH 5.0) were added. A sheet of PVC membrane consisting of 1.0 wt.% bathophenanthroline and 64.8 wt.% o-NPOE was then placed in the sample solution and stirred with a magnetic stirrer at 60°C. After stirring for a fixed time, the absorbance of the red membrane was measured at 538 nm using a spectrophotometer. The iron concentration in the sample solution was calculated using a calibration graph. The detectable concentration of iron was in the range 6.80 × 10 −7 −4.29 × 10 −5 M. Seven repeated measurements with 2.15 × 10 −5 M iron under the same conditions gave an average, relative standard deviation and repeatability for the absorbances of the membranes of 0.180, 4.3% and 0.0215, respectively.