Spatially resolved absorption measurements of antimony atom formation and dissipation in quartz tube atomizers following hydride generation

Abstract

The cross-sectional distribution of free antimony atoms generated from admission of stibine into quartz tube atomizers was measured by atomic absorption spectrometry. A CCD camera was used for the spatially resolved detection. In the unheated flame-in-tube atomizer, the highest free atom concentration was found near the tube axis, decreasing towards the walls. The free atom distribution was not influenced by atomization conditions such as purge gas flow rate and oxygen delivery. Significant changes in the free atom distribution were obtained by changing the position of the oxygen delivery capillary tip. Analyte reactions within the tube were revealed from an analysis of the curvature of the calibration curve. In the externally heated atomizer (900°C), the free atom distribution was much more homogeneous compared to the unheated atomizer under analytical conditions. However, pronounced inhomogeneity (higher concentration of free atoms near the tube axis and in the regions close to the walls) was obtained at high Sb concentrations in a roll-over part of the calibration curve (over 300 ng ml −1). This is explained on the basis of free atom decay on the surface of polyatomic particles formed at high analyte concentrations. From a practical point of view, no effects caused by the inhomogeneous free atom distribution are to be expected in the heated `flameless' tubes, the most widely used in routine analysis, since cross-sectional inhomogeneity observed under typical working conditions was negligible.