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 mu g in 30 - 500 mi of a sample solution. The relative standard deviation for eight measurements at 0.5 mu g of iron(II) was 5.4%. The detection limit was 10 ng of iron(II) in 500 mi (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.