A radiotracer study on the volatilization and transport effects of thermochemical reagents used in the analysis of alumina powders by slurry electrothermal vaporization inductively coupled plasma mass spectrometry

A neutron-activated Al2O3 powder SRM 699 (NIST) containing the gamma-radiation emitting radionuclides Cr-51, Fe-59, Co-60 and Zn-65 has been used to study the influence of thermochemical reagents on the volatilization and transport efficiency for these trace elements in electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) of Al2O3 powders. From the signals in the gamma-spectra for the radiotracers it has been found that less than 2% of the elements Cr, Fe, Co and Zn is left back in a graphite furnace from Al2O3 powders at 2200 degrees C even without addition of a thermochemical reagent and the latter even was found to decrease the volatilization efficiencies. The recovery for the radiotracers on filters at the end of the transport tube as measured from the signals in the gamma-spectra, however, was found to increase in most cases (i.e. from about 10% to more than 20%) when Pd(NO3)(2), Pd(NO3)(2) +Mg(NO3)(2), PdCl2, IrCl3, SnCl2, AgCl, NaF, NH4Cl and NH4F were added at amounts generally used in electrothermal vaporization inductively coupled plasma mass spectrometry. However, when adding higher amounts as stoichiometrically required for a complete halogenation of the sample matrix in the case of AgCl, C8F15O2Na, IrCl3 or PdCl2 the transport efficiencies considerably decrease again. As shown in the case of NH4Cl the amount of thermochemical reagent used has to be optimized so as to obtain maximum analyte transport efficiencies. A comparison of the influence of NH4Cl on the transport efficiencies with its influence on the ETV-ICP-MS signals for Fe demonstrates the importance of transport efficiency changes for the effects of thermochemical reagents in electrothermal vaporization inductively coupled plasma mass spectrometry. (c) 2007 Elsevier B.V. All rights reserved.