Determination of iron in nickel-iron alloy thin films by FIA

A highly accurate method for the determination of iron in nickel-iron alloy thin films has been developed by applying the spectrophotometric detection of FIA. The method is based on the injection of reagent/sample/ reagent into carrier water and reaction at high temperature. Carrier solution (deionized water) was propelled by a 2 channel piston pump (flow rate : 1.0 ml/min), the reagent and the sample solution were injected in the following order; reagent (60 μl), sample (60 μl) and reagent (60 μl) by a 16-port injection valve. The reagent solution was prepared by dissolving 0.5 mM 4, 7-diphenyl-1, 10-phenanthrolinedisulfonic acid disodium salt (DPPS) and 10 mM ascorbic acid in 0.3 M sodium acetate buffer solution (pH 4.6). Ten meter long teflon tubing (0.5 mm i.d.) was used as a reaction coil and maintained at 95 °C. The absorbance of iron(II)-DPPS complex was measured at 535 nm using a flow cell (18 μl). At the sampling rate of 20 samples per hour, the relative standard deviation was 0.08% (n=14) for the determination of 1 ppm iron(III). The accuracy of the calibration curve {0.51.5 ppm iron(III)} was ±0.2%. Application of this method to a permalloy thin film, allowed iron in minute amounts of sample (ca. 0.10.3 mg) to be determined with high accuracy.