Photoacoustic Spectrometric Determination of Trace Iron(II) after Preconcentration on a Membrane Filter with a Finely Pulverized Anion-Exchange Resin

A sensitive method based on preconcentration on a membrane filter with a finely pulverized anion-exchange resin has been developed for the determination of iron(II) in water samples by photoacoustic spectrometry. Iron(II) reacts with 2-nitroso-5-(N-propyl-N-sulfopropylamino)phenol (Nitroso-PSAP) to form a water-soluble chelate anion, which is adsorbed on the resin at pH 8.0; the resulting resin is filtered through a membrane filter (13 mm in diameter). The resin with the membrane filter is inserted into a cell, and the intensity of the photoacoustic signal of iron(II) is measured at 826 nm. The calibration graph for iron(II) was linear over the range 0.05–0.8 mg in 30–500 ml of a sample solution. The relative standard deviation for eight measurements at 0.5 mg of iron(II) was 5.4%. The detection limit was 10 ng of iron(II) in 500 ml (20 ngFe l–1). The interference of various ions was studied and the optimum conditions were developed for the determination of iron(II) in mine-drainage and river-water samples.