Surface and gas phase temperatures of a tungsten coil atomizer

The electrothermal atomization of elements is critically affected by the volatility of the analyte and its compounds, the matrix constituents, the atomizer material and the surface and gas phase temperatures. There are scarce temperature data about the tungsten coil atomizer (TCA). This paper involves measurements of surface and gas phase temperatures of a TCA (Osrarn 150 W). Three strategies were adopted to assess the surface temperature: electric current measurements in each applied voltage to calculate resistivity and correlation of this latter parameter with temperature; melting points of organic and inorganic compounds in the 120-800 degreesC range, and optical pyrometer measurements in the 1000-3000 degreesC range. The first two methods led to at least estimate values and more accurate results were attained with the optical pyrometer. The gas phase temperature was estimated based on the two-line absorption method using tin as thermometric element. The data showed a pronounced difference between surface and gas phase temperatures that can reach values higher than 1000 degreesC depending on the applied voltage and observation height. Data are discussed considering thermochemical processes in a double layer tungsten coiled filament. (C) 2002 Elsevier Science B.V. All rights reserved.