Mechanistic studies on the vaporization and atomization of molecular and atomic species in an electrothermal vaporizer using spatial and temporal distributions

Some of the matrix effects associated with the vaporization of selected elements {dollar}rm(sp{lcub}59{rcub}Cosp+, sp{lcub}63{rcub}Cusp+, sp{lcub}133{rcub}Cssp+, sp{lcub}208{rcub}Pbsp+, sp{lcub}209{rcub}Bisp+, sp{lcub}238{rcub}Usp+){dollar} with electrothermal vaporization (ETV) inductively coupled plasma mass spectrometry (ICP-MS) were investigated. The temporal behaviour of water, HCl and HNO{dollar}sb3{dollar} showed that these species are retained in the ETV even after a pyrolysis temperature of 400{dollar}spcirc{dollar}C. In most cases, higher concentrations of acid resulted in higher signals suggesting that the acids may act as a physical carrier and improve the vaporization and mass transport of many elements to the ICP-MS.; Mechanisms of vaporization and atomization of elements which form refractory oxides and carbides with a heated graphite surface were studied. Vaporization curves of {dollar}rmsp{lcub}10{rcub}Bsp+{dollar} using ETV-ICP-MS reveal the temporal distribution of molecular and atomic boron species. Experiments using the ETV-ICP-MS showed that for graphite furnace atomic absorption spectrometry (GFAAS), pre-atomization losses as molecular species at temperatures well below the appearance temperature for boron account for poor sensitivity of this elements by GFAAS. Vaporization and atomization of boron was also investigated using digital imaging techniques with a CCD camera. Using and interference filter and a molecular absorption band which is coincident with the BO band at 254 nm, high concentrations of molecular boron species were localized in the centre of the graphite tube at low temperatures (1800{dollar}spcirc{dollar}C). At high temperatures (2600{dollar}spcirc{dollar}C), the molecular boron species ar probably reduced on the graphite tube wall and desorbed from the surface forming concentric rings of B (g) having different number densities.; Investigations of vaporization and atomization of uranium, yttrium and the Rare Earth Elements using ETV-ICP-MS and GFAAS were made. Investigations were also made on techniques to improve ETV-ICP-MS signal quality, sensitivity and to reduce memory effects associated with refractory carbide formation. the following methods for improving ETV-ICP-MS signal quality were established: (i) vaporizing the analyte from a tungsten surface; (ii) use of lower vaporization temperatures and (iii) use of 0.2% CHF{dollar}sb3{dollar} as gas-phase matrix modifier in the internal argon carrier flow.