Abstract
A simple and selective ion-exchange preconcentration technique is described for the graphite-furnace atomic-absorption spectrometric determination of trace amounts of iron in high-purity copper. Iron(III) was separated from large amounts of copper(II) by complexing iron(III) with sulfosalicylate, followed by passing the solution through a chloride-form anion-exchange column (Dowex1-X8, 3 ml) at a flow rate of about 5 ml min−1 in a 0.02 M chloride medium (pH = 3.2). The column was washed with 10 ml of 0.02 M hydrochloric acid, and then the adsorbed iron(III)-sulfosalicylate complex was eluted from the column with 10 ml of 2 M nitric acid. After anion-exchange separation, the iron contents were determined by GFAAS. Iron(III) could be quantitatively adsorbed on a small column (13 mm i.d. and 30 mm bed length) up to 200 ml of a sample solution. The calibration graph prepared with the standard iron(III) solution was linear over the concentration range of 1∼50 ng ml−1 with a relative standard deviation (n = 3) of 1.2% at 10 ng ml−1. The proposed method was applicable for determinations down to 0.16 μg g−1 of iron in copper with a preconcentration factor of 20. Such elements as Ag, Al, Bi and Sn were also adsorbed on the column, but the maximum permissible concentrations of these elements exceeded the concentrations normally found in high-purity copper. The optimized method can be applied to the determination of iron at the μg g−1 level or lower in high-purity copper samples with a recovery of more than 99%. The time required for an analysis was within 3 h.
