THE ROLE OF MODIFIERS IN ELECTROTHERMAL VAPORIZATION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY (ETV-ICP-MS) FOR THE DETERMINATION OF B, LA AND U

The role of modifiers in electrothermal vaporization inductively coupl ed plasma mass spectrometry (ETV-ICP-MS) for the determination of refr actory elements such as La or U and carbide forming elements such as B has been studied. Solutions of NH4F, NH4Cl, NH4Br, NaCl, NaF, NH4HSO4 , (NH4)(2)HPO4, the gaseous halogenated hydrocarbons CHF3 and CCl2F2 a nd HCl have been used as modifiers. The mechanism of the modifier effe ct and the influence of modifiers on sensitivity enhancement have been investigated. The sensitivity enhancements are great enough to achiev e absolute detection limits of 2-6 pg for boron and 10 fg for La and U . The signal reproducibility is 0.5-3.0% for a concentration of 1 mu g 1(-1) La and U, and 20 mu g 1(-1) boron. Therefore, by adding modifie rs, the use of ETV-ICP-MS can be extended to trace element determinati on of refractory and carbide forming elements in mu l amounts of sampl e.