Application of inductively coupled plasma mass spectrometry (ICP-MS) for trace metal determination in foods

Abstract

The application of inductively coupled plasma mass spectrometry (ICP-MS) for trace and ultra-trace metal determination in foodstuffs has been investigated. The ICP-MS technique was compared with electrothermal atomisation atomic absorption spectrometry (ETA-AAS) for Cd and Pb in three biological standard materials. Results for Mo and V by ICP-MS were compared with the certified values. The ETA-AAS gave results that were closest to the certified values, with good precision. The ICP-MS results were encouraging and compared well for Cd and Pb, with both ETA-AAS and the certified results. The precision was acceptable at the higher element concentrations but degraded considerably at the lower levels. An investigation into the causes of the poor precision revealed molecular interferences and instrument hardware were partially to blame. Noticeable improvements in accuracy and dramatic improvements in precision were then obtained. Molecular ion interferences over the 51–81 a.m.u. mass range were investigated using several chemical matrices (HNO₃, HCl, H₂SO₄, H₃PO₄, H₂O₂ and NH₃) and the results confirmed that dilute HNO₃ is the most suitable acid matrix. Data are presented on the problems of the determination of As and V in the presence of ⁵¹CIO⁺ and ⁷⁵ArCl⁺ and the possibilities for data correction explored.