Determination of trace amounts of copper in iron and steel by anodic stripping voltammetry after extraction of the matrix.

Abstract

A simple and highly sensitive method is described for the determination of copper in iron and steel based on differential pulse anodic stripping voltammetry using an iron (III) excluding technique by means of 4-methyl-2-pentanone (MIBK) extraction. A 3 cm3 aliquot of an acidic sample solution (4 mol dm-3 hydrochloric acid-0.5 mol dm-3 nitric acid) saturated with sodium chloride and 8 cm3 of the MIBK were transferred into an electrochemical cell, and iron (III) was extracted above 99.95% into MIBK phase after vigorous stirring for 1 min. Electrodes were inserted in the aqueous phase (bottom) without excluding the MIBK phase from the cell. Copper (II) remaining in the aqueous phase was electrodeposited on a rotating glassy carbon electrode at -0.8 V vs. Ag/AgCl for 5 min; the deposit was then anodically stripped at a scan rate of 50 mV s-1 to 0 V vs. Ag/AgCl. The calibration graph was linear over a concentration range (7.9∼78.7) × 10-7 mol dm-3 of copper (II) and passed through the origin. The detection limit (3σ) was 4.7 × 10-8 mol dm-3. The determination of 1.62 to 138 μg g-1 of copper in iron and steel was achieved with good precision and accuracy within ca. 50 min. The possible interferences have been evaluated. The proposed method is applicable to the determination of copper (II) down to 1.3 μg g-1 in 40 mg cm-3 of iron (III) for a deposition time of 5 min.