Flow injection systems employing potassium peroxydisulphate as oxidizing reagent, immobilized on the anionic exchange resin AG1-X8 are proposed for spectrophotometric determination of nickel in steel alloys and for the speciation of iron (III)/iron (II) in waters. The flow networks were designed to provide facilities to perform on line analyte oxidation and resin reconditioning steps. The feasibility was ascertained by determining nickel in acid solutions of steel alloys and performing speciation of iron (III)/iron (II) in waters, using as chromogenic reagents dimethylglyoxime for nickel and potassium thiocyanate for iron. Profitable features such as a throughput of 80 and 60 samples per hour, 1.0 and 1.5% (n = 10) as relative standard deviations for nickel (21.5% m/m) and iron (III) (3.17 mg L-1), low reagents consumption (10 and 3.5 mg of potassium peroxydisulphate, 8.0 mg dimethylglyoxime and 5.4 mg of potassium thiocyanate, for nickel and iron, respectively) were observed. The accuracy for both procedures were ascertained by applying paried t-test between results obtained with flame atomic absorption spectrophotometry (FAAS) for Ni and 1,10-phenantroline spectrophotometric method for Fe (II), and no significant difference at 95% confidence level were observed.
flow analysis; immobilized reagent; chemical speciation; steel alloys
