PARAMETER OPTIMIZATION OF ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY FOR OLIGOELEMENT DETERMINATION IN STANDARD REFERENCE MATERIALS

The operational parameters of the graphite furnace for electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) , i.e. the internal carrier gas flow rate, the total carrier gas flow rate, the sample pretreatment temperature and the volatilization tempe rature, are optimized for oligoelement determinations (As-75, Be-9, Cd -112, Cr-50, Cu-65, Rh-103, Sb-123). The volatilization temperatures o f As and Cr are compared to those obtained by graphite furnace atomic absorption spectrometry (GFAAS). Several modifiers Mg(NO3)(2), Pd(NO3) (2), Mg(NO3)(2)/Pd(NO3)(2), Ni(NO3)(2), KI, (NH4)H2PO4 have been teste d using the concentrations recommended for GFAAS. The concentration of Mg(NO3)(2) alone and in combination with NaCl has been varied to find the optimal modifier conditions. ETV-ICP-MS signal enhancements by a factor of 10 to 130 respective to those of conventional nebulization h ave been obtained. The optimized parameters are evaluated by analyzing the water standard reference NIST 1643c and the aqua regia solution o f the lake sediment reference material BCR 280.