Beam-shaped electrothermal graphite tube furnace for atomic-absorption spectrophotometry

Abstract

Commercial graphite tubes (Massmann type) generally have a cylindrical shape and only a portion of the internal volume is available for absorption, owing to the geometry of the focused light beam. The aim of this work was to find the best geometry of the atomisation chamber to exploit the absorbing power of the optical system.Starting from the geometry of the light beam of an atomic-absorption spectrophotometer (Pye Unicam SP1900), the size and geometry of the tube have been defined. The temperature distribution along the axis of the tube, the diffusion of the atomic vapour from the centre to the ends of the tube and the residence time of the atoms within the tube were studied to determine their influence on the analytical sensitivity.As theoretical calculations demonstrated that the improved tube should give an appreciable enhancement of the sensitivity, a graphite tube was constructed according to this new geometry. The experimental results obtained with different elements confirmed the expected improvement in the analytical performance.