We attempted a simple pretreating method consisting of solid-phase extraction using bonded silica with octadecyl (C18) as the solid-phase sorbent to determine trace elements in pure iron samples by means of inductively coupled plasma mass spectrometry (ICP-MS). The isotope dilution method was used along with the method mentioned above to ensure precise determination of Ni. We dissolved the sample of 1.00 g by nitric and hydrochloric acid, subsequently adding tartaric acid as a masking agent. The analytes could be separated by sodium diethyldithiocarbonate (DDTC) as chelate from the matrix by solid-phase extraction after adjusting the pH and adding DDTC. The optimum condition was 0.1 kmol/m3 DDTC, 4 cm3; tartaric acid, 15 g as the masking reagent; pH, 10.6; C18, 0.5 g as the solid-phase solvent; and 6 kmol/m3 nitric acid, 5 cm3 as eluate including 1% hydrogen peroxide. In this method, some trace elements, such as Bi, Pb, Ni, Co, Cu, Cd and In, were determined by ICP-MS using the eluate. The limits of detection in ng/g were Co 0.38, Ni 0.43, Cu 2.90, Cd 0.93, In 0.23, Pb 0.23 and Bi 0.42. The RSD was 2% or less for each element. We precisely determined the Ni content by jointly using the isotope dilution method.
