A longitudinally heated graphite furnace for a longitudinal magnetic field. Formation of absorbance signals

Abstract

The physical properties and analytical characteristics of a longitudinally heated graphite furnace placed in a longitudinal a.c. magnetic field have been investigated. This graphite furnace is used in a commercially available (Cortech Ltd., Russia, model Z.ETA) Zeeman atomic absorption spectrometer. The analytical signals presented by convolution of the supply and removal functions have been determined for a number of elements (Cd, Pb, Cu, Al, Mo) with various behavioural patterns in a graphite furnace. The release of analyte atoms from the wall of a furnace is described by a first-order rate constant with Arrhenius-type temperature dependence. It has been shown that the supply function is determined mainly by the heating rate of the furnace. At a furnace heating rate of 9.5 K (ms) −1 the atomization time is ∼ 30 ms. A diffusion model of atom transfer satisfactorily predicts the residence time of analyte atoms. The gas temperature has been measured by the two-line method with approximation of the tails of the absorbance pulses by exponential functions. The values of the residence time for the Z.ETA furnace are 100–200 ms. Satisfactory agreement of simulated and experimental absorbance signals has been obtained. Characteristic masses of elements for the Z.ETA furnace have been measured and compared with characteristic mass data for known atomizers.