Use of negative chemical ionization mass spectrometry for the trace analysis of metals.

The synthesis of various volatile and thermally stable derivatives of metals ions has permitted the use of conventional mass spectrometry for trace metal analysis. This paper reviews the development of the field using electron impact and chemical ionization mass spectrometry. This latter methodology produces simple mass spectra that enable complex mixtures to be analyzed. In addition the use of negative ion detection has produced selective ionization since many metal chelates contain heteroatoms which are electronegative. A discussion of the use of this general methodology for trace metal analysis is included, together with its applications to the analysis of ruthenium in automobile exhaust emissions and iron in red blood cells from laboratory rats. The future use of this methodology is expected to be for the monitoring of stable metal isotopes. This procedure could be used to follow these tracers in clinical and environmental studies and it is expected that their use will replace radioactive isotopes in most studies.