Abstract

Microwave plasma torch (MPT) is a simple and low power-consumption ambient ion source. When MPT
mass spectrometry is applied in the detection of some metal elements, the metallic ions exhibit some
novel features which are different from traditional ICP mass spectrometry and may be helpful for the
metal element analysis. Zinc and cadmium both are important transition metals with wide applications
in modern industry. Here, we presented the research results of the MPT mass spectra of zinc and cadmium
elements by a linear ion trap mass spectrometer (LTQ) both in positive and negative modes. Without
any sample pretreatment, the aqueous samples were pneumatically nebulized and the aerosols were
generated. The dried aerosols were introduced into the plasma through the central tube of the MPT to
generate the complex metallic ions. For the positive composite ions of zinc and cadmium, the general
forms are the hybrid of M(NO3)·nOH·mH2O, thus the MPT mass spectra are extremely complicated and
unsuitable for the quantitative monitoring. However, the MPT negative ionic of zinc and cadmium is quite
regular in the forms of M(NO3). We also showed that the limit of detection (LOD) for zinc and cadmium
in negative mode can be achieved at the level of 10 g/L (ppb). Therefore, the negative mode MPT mass
spectrometry can be used as one of the alternative supplements of ICP-MS applied in on-line monitoring
of zinc and cadmium metal ions in water at trace levels, which will be promising in the field analysis of
metal elements and the rapid water quality inspection.

Keywords: Microwave plasma torch; Linear ion trap mass spectrometry; Zinc; Cadmium; Water inspection

2016-蒋涛-Int. J. Mass Spectrom.pdf