ICP-MS determination of trace amounts of zinc, copper, lead and bismuth in high-purity aluminum after electrolytic separation

A simple electrolytic preconcentration technique is described for the simultaneous determination of trace amounts of zinc, copper, lead and bismuth in high-purity aluminum by inductively coupled plasma-mass spectrometry (ICP-MS). The technique is based on the electrochemical deposition and dissolution of trace elements. The optimized operating conditions were as follows: the desired trace metal ions in 1 ml of a diluted hydrochloric acid solution (pH = 2.3) were deposited in a mercury-plated glassy-carbon electrode (surface area of about 2 cm(2)) as metals at (-)1.30 V vs. SCE for 90 min; the resulting deposits were then anodically dissolved in another solution (1 ml of 0.1 M nitric acid) at 0.10 V vs. SCE for 1 min. After electrolytic separation, the concentrations of the desired elements were determined by ICP-MS. Deposition yields greater than 97% were generally obtained in the presence of 2 mg ml(-1) aluminum(III). The calibration graphs of the desired elements were linear with relative standard deviations (n = 5) of less than 5.7% at the 2 ng ml(-1) level for each of the elements. The possible interferences have been evaluated, The minimum limits of determinations (10sigma) of zinc, copper, lead and bismuth in aluminum, calculated from repeated measurements n = 10) of a blank solution, were approximately 0.35, 0.18, 0.05 and 0.03 mug g(-1), respectively. The proposed method was successfully applied to the determinations of zinc, copper, lead and bismuth at the mug g(-1) level or lower in two high-purity aluminum samples. The time required for an analysis was within 3 h.