Anal. Chem. 1981, 53, 1437-1442
1437
Influence of Instrumental Response Time on Interference Effects in Graphite Furnace Atomic Absorption Spectrometry Erlk Lundberg" and Wolfgang Frech Department of Analytical Ghemistty, University of Umea, S-901 87 Umea, Sweden
The Influence of Instrumental response time on observed Interference effects in giraphite furnace atomic absorption spectrometry was Illustrated by the systems lead In sodlum chlorlde or sodlum nitrate and manganese and beryllium In aluminum nltrate. For the accomplishment of these studies, a spectrometer with a small time constant and an on-line data acqulsitlon system was used. It Is shown that concomltants can affect the vaporiratlon characterlstlcs of the analyte by changing (i) the atomlratlon Interval and/or (11) the rate of atom formation. From the experlmental results It Is concluded that such changes cannot be established adequately when the detector/readout system has a too slow response tlme, which is the case In miany commercial instruments. This means that many emplirlcal studies of interference effects reported In the literature, where such instruments have been used, are of llmited value.
The degree of observed interference effects in graphite furnace atomic absorption spectrometry (GFAAS) is determined by two different categories of factors which should be considered separately. The first category concerns the basic principles which underlie this technique and includes all factors which bring about changes in the efficiency of free atom formation or which alteir the temporal as well as spatial distribution of free atoms within the measuring cell. Interference effects belonging to thiei category originate from changes in the chemical or physical properties of the sample or the measuring cell and are referred to as chemical and physical interferences. The second category is instrumental in origin and includes (i) the ability of the spectrophotometer to discriminate the specific absorbance from the absorbance caused by particles, molecules, or atoms and (ii) changes in peak shapes as well as displacements of peak maxima arising from a too slow temporal response of the detector/readout system. The absorption signal obtained during the vaporization of atoms in the cell is time dependent and can be monitored with a relatively small error (
