Abstract

The vertical spatial distribution of Sn in the graphite furnace was determined in the presence of 0.5% HCl (standards) and 10 µg of KCl, K₂SO₄, and NiSO₄, with and without 5 µg of Pd, using a spectrometer capable of measuring spatially resolved absorbance. A normal gradient (decreasing concentration with increasing height in the furnace) was observed for Sn in HCl and KCl. This gradient was dramatically reversed in the presence of K₂SO₄ (at all pyrolysis temperatures) and NiSO₄ (at pyrolysis temperatures below 900 °C) and was accompanied by poor analytical recoveries. Accurate analytical recoveries and a normal gradient were obtained for NiSO₄ when a pyrolysis temperature of 900 °C was used. Pd yielded normal gradients statistically different (steeper) than those obtained with Sn Standards in HCl. The gradient for Sn in the presence of Pd was not affected by 10 µg of KCl, K₂SO₄, and NiSO₄. Accurate analytical recoveries were obtained for Sn in Pd in all the matrices tested in this study and at all pyrolysis temperatures. The change in the Sn gradient induced by KCl, K₂SO₄, and NiSO₄ resulted in photometric errors that are problematic for conventional, line-source AAS. Selection of the height of the viewing region within the furnace can exacerbate or improve the analytical recoveries. The constant Sn gradient established by Pd removed photometric error as an error source in the determination of Sn.