SIGNAL ENHANCEMENT EFFECT OF HALOGEN MATRIX IN ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

In tungsten furnace electrothermal vaporization(ETV)-inductively coupl ed plasma mass spectrometry(ICP-MS), the presence of halogen matrices caused a signal enhancement for volatile elements such as Zn, Cd and P b, whose halides melting and boiling points were relatively low. In or der to clarify the mechanism of signal enhancement in ETV-ICP-MS, the effects of chemical interaction between analytes and halogen matrices on the surface of ETV furnace, the transport efficiency of vaporized a nalytes from the furnace into the ICP and the physical properties of t he ICP itself and of the micro plasma (interface plasma) in the interf ace region between the sampling and the skimmer cones were investigate d by atomic absorption and atomic emission spectrometry. Among the eff ects mentioned above, neither the chemical interaction on the surface of the ETV furnace nor the transport efficiency of vaporized analytes could be related to the analyte signal enhancements. The degree of enh ancement was found to depend on the ionization potential of the coexis ting halogen and was not caused by a variation in the physical propert ies of the ICP but rather by a variation of those of the interface pla sma. These results suggest that the halogen matrices may affect the ph ysical properties of the interface plasma, contributing to the promoti on of the ionization of analytes.