An electrothermal vaporization unit with axially focusing convection upstream and influence of modifiers. Part I: Experimental

A novel, further improved construction of an electrothermal vaporization (ETV) unit is described, and new measurements are presented. Its main feature is an upstream within a vertical tube creating an axially focusing convection zone, where the condensation occurs in a laminar flow predominantly apart from the colder walls. The upstream is shielded against incandescent emission of the graphite furnace (GF) and surrounded with different cooling gas flows, that have additional focusing effect. The transported ETV generated aerosol is electrostatically precipitated onto a secondary platform that is subsequently analyzed for the transported analytes. Transport efficiencies (TEs) for Cu, Fe, Mn, Ni, and Pb are studied using a continuum source coherent forward scattering multi-element spectrometer coupled to the ETV. Increasing TE is observed with the ageing of the GF. The effect is presumably ascribed to the growing content of carbon particulates released during the vaporization. A positive impact of K and Pd modifiers in microgram amounts foremost on the TEs of more volatile species is observed and discussed.