Determination of Zinc in Iron and Steel by Reversed-phase High-performance Liquid Chromatography with α, β, γ, δ-tetrakis(4-carboxyphenyl)porphine as a Precolumn Derivatizing Agent

A novel method for the determination of trace amounts of zinc in iron and steel has been demonstrated by a reversed-phase HPLC using α, β, γ, δ-tetrakis(4-carboxyphenyl)porphine as a derivatizing reagent. Certified reference materials of iron and steel were used to prepare digestive samples by decomposition followed by 4-methyl-2-pentanone extraction and sulfuric acid fuming. The digested sample solutions were derivatized with Cd(II)-α, β, γ, δ-tetrakis(4-carboxyphenyl)porphine solution in ammonium buffer (pH 9.0) solution, using 5-sulfosalicylate as a masking reagent. Aqueous-acetonitrile (45:55 w/w) containing 7.0 × 10-2 mol kg-1 of lactate buffer (pH 4.15) was used as an eluent and was monitored at 422 nm.A linear calibration was observed in the concentration range from 1 × 10-8 mol dm-3 to 1 × 10-6 mol dm-3. The detection limit (3σ) of Zn(II) was 1.3 × 10-9 mol dm-3, which corresponded to 0.32 ppm in iron and steel samples. The recoveries of zinc added to the digested solution of iron and steel were with in 97 to 107%. The good recovery and high sensitivity indicate that the proposed system is of great promise for the determination of zinc present in iron and steel.