Quality assurance of arsenic, lead, tin and zinc in copper alloys using axial inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS)

Abstract

Results for As, Pb, Sn and Zn are reported for five copper alloys. Following dissolution in a refluxing HCl-HNO ₃ mixture and subsequent dilution, the elements were determined by inductively coupled plasma time-of-flight mass spectrometry (ICP-TOF-MS) using In as an internal standard. The following isotopes: ⁶⁴ Zn, ⁶⁶ Zn, ⁶⁷ Zn, ⁶⁸ Zn, ⁷⁰ Zn, ⁷⁵ As, ²⁰⁶ Pb, ²⁰⁷ Pb ²⁰⁸ Pb, ¹¹⁵ In, ¹¹⁶ Sn, ¹¹⁸ Sn and ¹²⁰ Sn were monitored and the intensity ratios to ¹¹⁵ In as an internal standard were used. The analytical results were compared with results obtained by flame atomic absorption spectrometry (FAAS) for assessment of accuracy. The results agreed fairly well, except for Zn in some compositions, which was due to background interference effects, and for Sn, where dissolution problems occurred. The relative standard deviations, % RSDs, for six replicate measurements of the elements in each copper alloy were in the range 2.0-6.1% for As, 3.8-11.0% for Pb, 1.4-9.4% for Sn and 3.6-12.9% for Zn. Uncertainty budgets for Sn and Zn associated with these determinations are described. The detection limits (3s criterion) in the solid materials with a 1.0 g sample intake and appropriate dilutions were 0.7 µg g ^–1 for Pb, 2.5 µg g ^–1 for Sn, 11 µg g ^–1 for As and 15 µg g ^–1 for Zn.