MATRIX VAPORS AND PHYSICAL INTERFERENCE EFFECTS IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY .1. END-HEATED TUBES

Two types of physical interference effects in graphite furnace atomic absorption spectrometry were identified and investigated. The first type concerns analyte trapping in the cooler ends of HGA-type atomizers. Trapping was investigated using analytes of different volatilities (Cd, Pb, Mn, Ga and Au) in the presence of a Ag matrix. The total decrease in the analyte signal depended on the atomization temperature used and on the volatility of the analyte. By using mini-flow conditions, instead of gas-stop, trapping could be eliminated. At the same time, for some elements, the peak area signals in Ar were increased by up to 15% in the presence of Ag in comparison to aqueous solutions. This second tv e of interference is explained by an increased analyte residence time due to high partial pressures of matrix vapours, which change the diffusion coefficients of the atoms. This type of interference effect was also observed for a K2SO4 matrix when Ga and Al were used as analytes.