Investigation of spectral interference in the determination of Pb in road dust using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Abstract

Direct solid sample analysis using graphite furnace atomic absorption spectrometry (GF AAS) is an attractive alternative because no sample pretreatment is necessary. However, the major obstacles of this technique are spectral interference and the limited background correction capability of conventional line source AAS instruments. The introduction of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) has brought about a significant change in this direction due to its superior background correction capabilities. In this study, a method has been developed for the determination of Pb in road dust using HR-CS GF AAS and direct solid sample analysis. The analytical lines at 261.418 nm (2.1% relative sensitivity), with detection of 1 pixel, and at 283.306 nm (42% relative sensitivity), with side pixel evaluation, were used for Pb determination. Pyrolysis and atomization temperatures were 900 °C and 2300 °C, respectively, using a mixture of Pd and Mg as the chemical modifier. Twelve samples and three certified reference materials (CRMs) have been analyzed. A significant structured background has been observed at the optimum atomization temperature, which overlapped with the analyte atomic absorption wavelength. The background has been identified as AlCl, SiO and SiS molecules at 261.418 nm, and SiS at 283.306 nm. Least-squares background correction (LSBC) has been applied after the identification of the diatomic molecules and the results obtained for the CRMs were in agreement with the certified ones. The use of this correction technique allowed the elimination of spectral interference in the determination of Pb in road dust.